WO2022243575A2

WO2022243575A2 - Battery system and method of assembly

Info

Publication number: WO2022243575A2
Application number: PCT/EP2022/063945
Authority: WO
Inventors: Arjun Mehta; Sean Cleary
Original assignee: Edge Mobility Ltd
Current assignee: Edge Mobility Ltd
Priority date: 2021-05-21
Filing date: 2022-05-23
Publication date: 2022-11-24
Anticipated expiration: 2023-11-21
Also published as: WO2022243575A3

Abstract

A battery system and method for assembling such a system. The battery system comprises an enclosure, an array of cells within the enclosure, a coolant comprising a dielectric fluid that is electrically non-conductive, and a PCB installed over the array. The PCB comprises a substrate, a first conductive layer on a side of the substrate opposite the array, the first conductive layer comprising a plurality of cell-bonding pads, and an array of through-holes, each of the through-holes being adjacent to at least one of the cell-bonding pads. The PCB includes positive and negative power pads conductively coupled to the cell-bonding pads to create a power circuit that allows for the transfer of power to and from the array of cells. The PCB includes mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use. Terminals of the cells are wire-bonded to corresponding cell-bonding pads on the PCB through the through-holes. At least part of one or more cells and at least some of the electronic components are in direct contact with the coolant when the battery system is in use. The coolant enables the transfer of heat from one or more of the cells to one or more of the electronic components and vice versa.

Description

BATTERY SYSTEM AND METHOD OF ASSEMBLY

FIELD

The present invention relates to battery systems and methods of assembly.

BACKGROUND

Battery systems can comprise an array of battery cells, connected together and controlled by a battery management system.

SUMMARY

According to a first aspect, there is provided a battery system comprising: an enclosure; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; a coolant comprising a dielectric fluid that is electrically non-conductive; and a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell bonding pads; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; wherein: the cell terminals on the top surface of the cells are wire-bonded to corresponding cell-bonding pads on the PCB through the through-holes; at least a part of an outer surface of one or more cells and at least some of the electronic components are in direct contact with the coolant when the battery system is in use; and the coolant enables the transfer of heat from one or more of the cells to one or more of the electronic components and vice versa. The PCB may comprise a further conductive layer on an opposite side of the substrate from the first conductive layer, wherein one or more of the electronic components are mounted to mounting pads on the further conductive layer.

The electronic components installed onto the mounting pads on the PCB may comprise heating elements for heating the coolant.

The heating elements may take the form of balancing resistors for use in balancing voltages of the cells.

The battery system may comprise at least 10 of the heating elements, at least 25 of the heating elements, at least 50 of the heating elements, or at least 100 of the heating elements.

The electronic components installed onto the mounting pads on the PCB may comprise cooling elements for cooling the coolant.

The heating and/or cooling elements may be mounted in a region of the PCB above the array of cells.

The heating and/or cooling elements may be mounted in a region of the PCB within which the cell-bonding pads are located.

The heating and/or cooling elements may be distributed so as to provide even heating and/or cooling of the array of cells.

The electronic components installed onto the mounting pads on the PCB may comprise temperature sensors for providing signals to a battery management and/or monitoring system (BMS).

At least some the electronic components installed onto the mounting pads on the PCB may together comprise a BMS.

The enclosure may comprise a scaffolding that locates the array of cells and provides a flow path for the coolant so that the coolant can pass across the cells when the battery system is in use.

The scaffolding may comprise a plurality of channels, wherein each channel is arranged to provide a flow path for the coolant so that the coolant passes across the cells, preferably wherein each scaffolding comprises at least three channels, at least six channels, and/or at least ten channels.

The PCB may comprise transfer holes/cut-outs, arranged to align with the channels of the scaffolding, such that the coolant enters the channels of the scaffolding and/or leaves the channels of the scaffolding by passing through the transfer holes/cut-outs of the PCB.

One or more temperature sensors may be mounted on the PCB adjacent one or more exits through which the coolant leaves the channels of the scaffolding.

One or more temperature sensors may be mounted on the PCB adjacent one or more entrances through which the coolant enters the channels of the scaffolding. The battery system may comprise a plurality of the temperature sensors mounted adjacent the exits, and one or more temperature sensors mounted adjacent the entrances, wherein the number of temperature sensors located at the exits is greater than the number of temperature sensors located at the entries.

The temperature sensors may be arranged to: determine a faulty battery cell; and/or determine a temperature distribution in the coolant; and/or control the operation of one or more cells, preferably in dependence on the temperature distribution in the coolant; and/or determine a temperature of a cell based on a temperature of the coolant; and/or control the operation of a pump, preferably in dependence on the temperature distribution in the coolant.

The heating and/or cooling elements may be arranged to operate in dependence on a/the temperature sensor(s) in the battery system.

The electronic components installed onto the mounting pads of the PCB may collectively perform some or all the functions of a battery monitoring and/or management system (BMS).

According to a second aspect, there is provided a battery system comprising: an enclosure; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell-bonding pads, wherein the cell terminals on the top surface of the cells are wire-bonded to corresponding cell bonding pads on the PCB through the through-holes; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; a positive power connector, wherein a top surface of the positive power connector is internal to the enclosure and positioned adjacent to the positive power pad, and is wire-bonded to the positive power pad of the PCB; and a negative power connector, wherein a top surface of the negative power connector is internal to the enclosure and positioned adjacent to the negative power pad, and is wire-bonded to the negative power pad of the PCB.

The enclosure may comprise a first enclosure aperture and a second enclosure aperture; the positive power connector may electrically couple the inside of the enclosure to the outside of the enclosure through the first enclosure aperture, such that the positive power connector is electrically accessible from outside of the enclosure; and the negative power connector may electrically couple the inside of the enclosure to the outside of the enclosure through the second enclosure aperture, such that the negative power connector is electrically accessible from outside of the enclosure.

Each of the positive power connector and the negative power connector may comprise a solid block formed from a conductor, the solid blocks being exposed within the enclosure, and exposed outside the enclosure on the other sides of their respective enclosure apertures.

The enclosure may comprise one or more internal shelves on which the first and second enclosure apertures are located.

The battery system may comprise one or more gaskets between the one or more shelves and the positive and negative power connectors, wherein the one or more gaskets comprise one or more gasket apertures through which the positive and negative power connectors pass, the one or more gaskets creating a seal between the enclosure and the positive and negative connectors respectively.

The positive and negative power connectors may comprise an insulating retainer to galvanically isolate conductive portions of the respective power connectors from the enclosure.

The or each insulating retainer may comprise a supporting lip extending under the corresponding power pad on the PCB, the supporting lip being configured to galvanically isolate the enclosure from the PCB.

The insulating retainer may comprise a supporting lip extending under the corresponding power pad on the PCB, the supporting lip being configured to support the PCB whilst the wire-bonds are being formed between the power connector and power pad.

The positive and negative power pads may both be disposed at a same edge of the PCB.

The array of cells may define a first sub-array corresponding to a first side of the PCB in plan, and a second sub array corresponding to a second side of the PCB in plan, the second side being opposite the first side, the first sub array and second sub-array comprising an equal number of cells, and the power circuit may comprise a first conductive path extending through the first side and the first sub-array, and a second conductive path extending through the second side and the second sub-array, the first and second conductive paths being joined at an edge of the PCB opposite to the edge upon which the positive and negative power pads are disposed, configured such that current flows from the positive power pad through the first conductive path in a first direction, and then through the second conductive path to the negative power pad in a second direction substantially opposite to the first direction. The battery system may comprise a third conductive path joining the first and second conductive paths, configured such that current flows through the third conductive path in a direction generally normal to the first and second directions.

The electronic components may comprise one or more switching components for selectively opening and closing the power circuit, and the switching component(s) may be disposed at an opposite edge of the BMS to the positive and negative power pads.

The switching component(s) may be positioned at a mid-point of the power circuit.

The number of wire bonds between each power connector and its corresponding power pad may be selected such that in the event of an over-current situation, the wire bonds will act as a fuse and melt.

According to a third aspect, there is provided a method of assembling the battery system of any other aspect, comprising: lowering the positive and negative power connectors into the enclosure; lowering the PCB into position above the array of cells, such that the positive connector is positioned adjacent to the positive power pad and the negative connector is positioned adjacent to the negative power pad; and making wire-bonded connections between the cell terminals and the cell-bonding pads, and between the top surfaces of the power connectors and the corresponding power pads.

The method may comprise: prior to lowering the positive and negative power connectors into the enclosure, placing the one or more gaskets onto the one or more shelves such that the gasket apertures are aligned with the first and second enclosure apertures; and fixing the power connectors to the enclosure so as to compress the one or more gaskets between the one or more shelves and the power connectors, thereby sealing the first and second enclosure apertures.

The method may comprise fastening the PCB to the enclosure prior to making wire-bonded connections between the cell terminals and the cell-bonding pads.

According to a fourth aspect, there is provided a battery system comprising: an enclosure comprising a signal connector aperture; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; and a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell-bonding pads, wherein the cell terminals on the top surface of the cells are wire-bonded to corresponding cell bonding pads on the PCB through the through-holes; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; wherein the electronic components comprise a signal connector for transferring signals to and from the other electronic components, the signal connector passing through the signal connector aperture in the enclosure such that the signal connector is directly accessible from outside of the enclosure.

The PCB may comprise a further conductive layer on an opposite side of the substrate from the first conductive layer, wherein the further conductive layer comprises one or more of the mounting pads and wherein the signal connector is mounted on one of the mounting pads on the further conductive layer.

The enclosure may comprise a shelf through which the signal connector aperture passes.

The battery system may comprise a gasket between the shelf and the PCB, wherein the gasket has a gasket aperture through which the signal connector passes, the gasket creating a seal between the signal connector and the enclosure.

According to a fifth aspect, there is provided a method of assembling the battery system of any other aspect, comprising: disposing the array of cells within the enclosure; lowering the PCB into position above the array of cells such that the signal connector passes through the signal connector aperture; fastening the PCB to the enclosure; and making wire-bonded connections between the cell terminals and the cell-bonding pads.

The method may comprise: prior to lowering the PCB into position, placing the gasket onto the shelf such that the gasket aperture is aligned with the signal connector aperture; and fixing the PCB to the enclosure so as to compress the gasket between the shelf and the PCB, thereby sealing the signal connector aperture.

The method may comprise: prior to lowering the PCB into position, placing the gasket onto the PCB such that the gasket surrounds the signal connector; and fixing the PCB to the enclosure so as to compress the gasket between the shelf and the PCB, thereby sealing the signal connector aperture.

According to a sixth aspect, there is provide a PCB, the PCB comprising: a substrate; a first side, the first side comprising first connector mounting pads to which a first connector can be mounted; and a second side opposite the first side, the second side comprising second connector mounting pads to which a second connector can be mounted; the first and second connector mounting pads having at least one conductive connection to the PCB in common, such that the first connector or the second connector can be mounted to the respective first and second connector mounting pads, depending upon the use to which the PCB is to be put.

The first and second connector mounting pads may have the same conductive connections to the PCB.

The first and second connector mounting pads may be coincident with each other.

The PCB may comprise: a first gasket sealing surface surrounding the first connector mounting pads; and a second gasket sealing surface surrounding the second connector mounting pads.

The PCB may comprise: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell-bonding pads; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use. According to a seventh aspect, there is provided the battery system of any aspect, comprising the PCB of the sixth aspect.

According to an eighth aspect, there is provided the PCB of the sixth aspect, for use in at least first and second related products, wherein the first product uses a first connector mounted to the first connector mounting pads, and the second product uses a second connector mounted to the second connector mounting pads.

According to a ninth aspect, there is provided a first product comprising the PCB of the sixth aspect, and a second product comprising the PCB of the sixth aspect, wherein: the PCB of the first product comprises a first connector mounted to the first connector mounting pads; and the PCB of the second product comprises a second connector mounted to the second connector mounting pads.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a printed circuit board (PCB);

Figure 2 is a perspective view of the reverse of the PCB of Figure 1;

Figure 3 is a plan view of the PCB of Figures 1 and 2;

Figure 4 is a plan view of the reverse of the PCB of Figures 1-3;

Figure 5 is a perspective view of a PCB populated with electronic components;

Figure 6 is a perspective view of the reverse of the PCB of Figure 5;

Figure 7 is a perspective view of the PCB of Figures 5 and 6, installed over an array of cells;

Figure 8 is a perspective view of the underside of the PCB and array of cells of Figure 7;

Figure 9 is a perspective view of an enclosure for a battery system;

Figure 10 is a perspective view of the enclosure of Figure 9, with an array of cells installed;

Figure 11 is a perspective view of the enclosure of Figures 9 and 10, with the PCB of Figures 5 and 6 installed over the array of cells; Figure 12 is a perspective view of an alternate battery system comprising the enclosure of Figure 9 and a lid;

Figure 13 is a plan view of the enclosure of Figures 9-11, showing wire bonded connections;

Figure 14 is a detailed perspective view of wire bonds between a cell-bonding pad and terminals of battery cells;

Figure 15 is a detailed perspective view of a power connector of the enclosure of Figure 11;

Figure 16 is a section through the power connector of Figure 15;

Figure 17 is a schematic section through the PCB of Figures 1-4;

Figure 18 is a plan view of the PCB and power connectors of the enclosure of Figure 11;

Figure 19 is a detailed perspective view of a PCB showing first connector mounting pads;

Figure 20 is a detailed perspective view of the reverse of the PCB of Figure 19 showing second connector mounting pads;

Figure 21 is the PCB of Figures 19 and 20, with a first connector mounted to the first connector mounting pads;

Figure 22 is the PCB of Figures 19-21, with a second connector mounted to the second connector mounting pads;

Figure 23 is a flowchart showing a method of assembling a battery system such as that shown in Figure 12;

Figures 24a, 24b, 24c, 24d and 24e show an embodiment of a scaffolding for locating the array of cells; and

Figure 25 shows a PCB installed on top of the scaffolding of Figure 24.

DETAILED DESCRIPTION

The following description relates to a printed circuit board (PCB), a PCB populated with electronic components to form a battery management and/or monitoring system (BMS), a battery system comprising such a PCB and BMS, a method of assembling such a battery system, and a PCB having first and second connector mounting pads on opposite sides of a substrate. These aspects have initially been developed with a focus on electric and hybrid vehicle systems. However, the skilled person will appreciate that the principles described have application beyond such systems. Referring to the drawings, and Figures 1-4 in particular, there is shown a printed circuit board (PCB) 100. The term "PCB" is used to refer to both a PCB without components, and PCB with electronic components installed. For example, in some implementations, electronic components are installed such that the PCB comprises a battery management and/or monitoring system ("BMS"). The term "populated PCB" can be used to refer to a PCB that includes at least some electronic components, which may or may not comprise some or all of such a BMS. The meanings of these terms are clear from their context.

PCB 100 is configured for installation over an array of cells with cell terminals. A non-limiting example of such an installation is described in detail below.

PCB 100 comprises a substrate 102. In the illustrated example, substrate 102 comprises a multi-layer fibreglass PCB substrate, but substrate 102 can take any suitable form. As shown in Figure 17, substrate 102 has several fibreglass layers 190, separated by intermediate copper layers 192. Each copper layer is of 1-3 oz thickness, for example.

PCB 100 also comprises first conductive layer, in the form of an upper conductive layer 104, disposed upon its surface. In the illustrated embodiment, upper conductive layer 104 comprises a layer of 2 oz copper, which has been etched or otherwise processed to form various conductive traces and other elements, as described in more detail below.

As best shown in Figures 1, 3, and 13, upper conductive layer 104 comprises a plurality of cell-bonding pads 106.

In general, each cell-bonding pad 106 is for making at least one wire-bonded connection from upper conductive layer 104 to at least one cell terminal. In the illustrated example, each cell-bonding pad 106 is for making a plurality of wire-bonded connections from the upper conductive layer 104 to cell terminals as described below.

PCB 100 also comprises an array of through-holes 108. Through-holes 108 are machined or otherwise formed through substrate 102. In general, each of through-holes 108 is adjacent to at least one of cell-bonding pads 106, although in the illustrated embodiment, each of through-holes 108 is adjacent to a pair of cell-bonding pads 106.

In general, each through-hole 108 is sized and configured to allow a wire-bonded connection to be made from at least one of the cell-bonding pads 106, through through-hole 108, to at least one cell terminal, as described in more detail below. In the illustrated embodiment, each through-hole 108 is sized and configured for allowing a plurality of wire-bonded connections to be made between a plurality of adjacent cell-bonding pads and the cell terminals of a plurality of the cells through through-hole 108, as described in more detail below.

In the illustrated example, each cell-bonding pad 106 is elongate in plan and extends parallel to the elongate direction of its adjacent through-hole 108. In other implementations, each cell-bonding pad can extend along more than one through-hole, and each such through-hole optionally allows access to one or more cells for the making of one or more wire-bonding connections. PCB 100 comprises mounting pads 110 for mounting electronic components for managing and/or monitoring the battery cells, as described in more detail below. Mounting pads 110 are connected with each other and other pads on PCB 100 via copper traces, wires, and/or other connectors. The electronic components can include, for example, at least one microcontroller or microprocessor, along with active and passive components that, when installed onto mounting pads 110, comprise a BMS for monitoring and/or management of the cells, as described in more detail below. In other implementations, some or all of the components of a BMS are provided separately for managing and/or monitoring the cells and other electronic components attached to PCB 100.

PCB 100 comprises a positive power pad 112 and a negative power pad 113. Positive and negative power pads 112 and 113 are conductively coupled to cell-bonding pads 106. In the illustrated example, positive power pad 112 and negative power pad 113 are disposed on the same side or edge 117 at one end of PCB 100. This may simplify power connections, as described in more detail below. However, power pads can be placed on different sides or edges relative to each other.

Conductive coupling between power pads 112, 113 and cell-bonding pads 106 is achieved by way of conductive traces 114 formed in conductive layer 104. In the illustrated example, conductive traces 114 are also connected to one or more additional conductive layers, such as intermediate copper layers 192, by way of via connections 116. The additional conductive layers can electrically mirror conductive traces 114. This mirroring of conductive traces 114 increases overall current-carrying capability without the need for, for example, bus bars or additional wiring. The skilled person will appreciate that any such additional conductive traces need not be the same size, shape or configuration as the conductive traces 114 they electrically mirror.

Cell-bonding pads 106, power pads 112, 113, conductive traces 114, and any additional conductive traces (not shown) together form a power circuit that allows for the transfer of power to and from the array of cells in use, as described in more detail below. Figure 18 shows the general current flow 194 through the power circuit. The skilled person will appreciate that the term "power circuit" means that the circuit carries a relatively high current relative to, for example, the current involved in signalling and control circuitry. As a non-limiting example, six cells in parallel, each capable of 30A peak current, would result in a power circuit carrying a peak current of around 180A, compared with signalling current that is typically less than a few amps, or sub 1A, or even sub 200mA. In general, the power circuit can be characterised by a current capacity that is an order of magnitude, two orders of magnitude, or more, greater than a current associated with signalling.

PCB 100 comprises balancing component mounting pads 118. Balancing component mounting pads 118 are for mounting balancing resistors and/or switches for balancing cell voltages under control of the BMS in use, as described in more detail below. At least some of the balancing component mounting pads 118 can be distributed through a region of the PCB within which cell-bonding pads 106 are located. For example, balancing resistors can be installed on balancing component mounting pads 118 disposed adjacent to one or more cell-balancing pads 106 connected to one or more cells for which the resistors provide balancing. This allows for heat generated by such balancing resistors to be distributed across PCB 100, which reduces excessive heat build-up that can occur when balancing resistors are localised in one area of a PCB. Balancing component mounting pads 118 can also be used for switching components that control current to balancing resistors, as described in more detail below.

In the illustrated example, balancing component mounting pads 118 are positioned such that, in use, balancing components installed onto the balancing component mounting pads can be used to heat cells that are wire- bonded to the PCB, as described in more detail below.

In the illustrated example, mounting pads include switching circuit pads 120 coupled within the power circuit. Switching circuit pads 120 are for mounting switching components for selectively opening and closing the power circuit, as described in more detail below. Switching circuit pads 120 are disposed at an opposite edge 121 of the PCB relative to the positive and negative terminals, although other positions are possible. Switching circuit pads 120 are positioned at a mid-point of the power circuit, which may offer physical advantages, such as improved space for the switching circuit. The skilled person will appreciate that other positions for switching circuit pads 120 are possible.

PCB 100 comprises a further conductive layer in the form of a lower conductive layer 122 on the opposite side of the substrate 102 from the upper conductive layer 104.

Lower conductive layer 122 comprises a plurality of thermal sensor mounting pads 124 for mounting thermal sensors for providing temperature signals to be monitored by the BMS in use, as described in more detail below.

Lower conductive layer 122 also comprises signal connector pads 180 for mounting one or more signal connectors for transferring data and signals to and from the BMS in use.

Turning to Figures 5 and 6, there is shown a populated PCB 126. Populated PCB 126 is based on the PCB of Figures 1 to 4, but with electronic components 128 installed onto the mounting pads that allow for monitoring and/or managing the cells when the battery system is in use. Electronic components 128 can include, for example, one or more microcontrollers or microprocessors (not shown), along with active and passive components (not shown). Optionally, the components provide some or all of the functionality required of a BMS.

Other components can also be installed on PCB 126. For example, thermal sensors in the form of, for example, thermistors 130 can be installed on thermal sensor mounting pads 124, balancing resistors 132 can be installed on balancing component mounting pads 118, and switching components (such as one or more relays or transistors, such as field effect transistors) 134 can be installed on switching circuit pads 120.

Populated PCB 126 includes a signal connector 178, connected to signal connector mounting pads 180 on the underside of populated PCB 126. Signal connector 178 extends away from the plane of substrate 102.

Additional supporting components and circuitry (not shown) can also be installed. This can include circuits and components for switching, scaling, filtering or otherwise modifying signals that pass around populated PCB 126 in use. The skilled person is familiar with such supporting circuits and components, and so they are not described in detail.

Once all components have been installed, populated PCB 126 can itself be installed as part of a battery system, such as battery system 136 shown in Figure 12. The skilled person will appreciate that populated PCB 126 can also be installed within battery systems differing from that shown in Figure 12.

Battery system 136 includes an enclosure 138. Enclosure 138 includes a generally planar base 140. A wall 142 extends upwards from edges of base 140 to define an interior space 144. Enclosure 138 is formed from aluminium, although any other suitable material or combination of materials may be used in construction of enclosure 138. Preferably, enclosure 138 is at least partly formed from electrically conductive materials to shield the populated PCB inside from electromagnetic interference. Flowever, electrically non-conductive materials may be used in particular implementations.

In the illustrated example, a support framework 146 (see Figures 7 and 8) is disposed within interior space 144. Support framework 146 is formed from a plastic, such as ABS plastic, although any other suitable polymeric or other material may be used in construction of support framework 146. Preferably, support framework 146 is formed from materials that are not electrically conductive. Populated PCB 126 is screwed to support framework 146 and enclosure 138 by screws 147 passing through holes 149 in substrate 102, although in other implementations, populated PCB 126 can be screwed only to holes 149 or enclosure 138, or to neither.

In other implementations, a separate support framework is not provided. In that case, battery cells can be self- supporting, and/or the enclosure itself can be configured to provide any necessary support.

Enclosure 138 includes a recessed shelf 160 along one edge. Shelf 160 is sized and configured to receive a corresponding portion of populated PCB 126, and includes a signal connector aperture 161.

Battery system 136 includes an array 148 of vertically orientated cells 150 disposed within interior space 144 of enclosure 138. Cells 150 are typically rechargeable, and can use any suitable rechargeable battery technology. In the illustrated implementation, alternate rows of cells 150 within array 148 are offset relative to each other, to reduce space between the cells and improve packing density.

In the illustrated implementation, each cell 150 has a positive cell terminal 152 and a negative cell terminal 154 at its upper end. Positive cell terminal 152 is centrally located on the upper end, and negative cell terminal 154 is located around a periphery of the upper end. Positive and negative cells terminals may alternatively be placed at opposite ends of the cells, or in any other suitable position.

In the illustrated implementation, array 148 of cells 150 defines a first sub-array of cells 150, indicated by arrow 181, and a second sub-array of cells 150, indicated by arrow 183. First sub-array 181 corresponds to a first side (in plan) of PCB 100, and second sub-array 183 corresponds to a second side (in plan) of PCB 100. First sub-array 181 and second sub-array 183 comprise an equal number of cells 150.

Current flow 194 shown in Figure 18 indicates the path taken by current when array 148 is providing power from cells 150. The power circuit providing this path comprises a first conductive path extending through the first side and first sub-array 181 of cells 150, and a second conductive path extending through the second side and second sub-array 183. The first and second conductive paths are joined at edge 121 of PCB 100, which is opposite to the edge upon which the positive and negative power pads 112 and 113 are disposed.

Current flows from positive power pad 112 through the first conductive path in a first direction, and then through the second conductive path in a second direction substantially opposite to the first direction.

Optionally, a third conductive path joins the first and second conductive paths. For example, the illustrated implementation comprises a third conductive path in the form of a large copper trace 185. Current flows through the copper trace 185 in a direction generally normal to the first and second directions.

The skilled person will appreciate that current flow is reversed when cells 150 are being charged.

Enclosure 138 comprises a first enclosure aperture 191 and a second enclosure aperture 193 formed through shelf 160. A positive power connector 156 and a negative power connector 158 are supported by recessed shelf 160, and extend through first enclosure aperture 191 and second enclosure aperture 193 respectively.

While positive power connector 156 and negative power connector 158 may take any suitable form to suit implementation requirements, in the illustrated implementation, both positive power connector 156 and negative power connector 158 comprise a solid block formed from a conductor. For example, positive power connector 156 comprises a positive terminal 164 in the form of a solid block of aluminium, copper, or any other conductive material or combination of materials, and negative power connector 158 comprises a negative terminal 168 in the form of a solid block of aluminium, copper, or any other conductive material or combinations of materials. Each block may be machined, moulded, forged, or otherwise manufactured into the required configuration. In the illustrated implementation, a solid block of aluminium is used, which provides a relatively low-cost and robust positive power connector 156 and negative power connector 158.

Positive power connector 156 electrically couples the inside of enclosure 138 to the outside of enclosure 138 through first enclosure aperture 191, such that positive power connector 156 is electrically accessible from outside enclosure 138. Similarly, negative power connector 158 electrically couples the inside of enclosure 138 to the outside of enclosure 138 through second enclosure aperture 193, such that negative power connector 158 is electrically accessible from outside enclosure 138. For example, one surface of positive terminal 164 is exposed within enclosure 138, and another surface of positive terminal 164 is exposed outside of enclosure 138 on the other side of the corresponding enclosure aperture. Similarly, one surface of negative terminal 168 is exposed within enclosure 138, and another surface of negative terminal 168 is exposed outside enclosure 138 on the other side of the corresponding enclosure aperture.

Positive power connector 156 comprises an insulating retainer 162 formed from a polymer, within which is disposed positive terminal 164. Similarly, negative power connector 158 comprises insulating retainer 166 formed from a polymer, within which is disposed negative terminal 168. Insulating retainers 162 and 166 are screwed to shelf 160 of enclosure 138, adjacent to respective positive and negative power pads 112, 113.

Insulating retainers 162 and 166 galvanically isolate their respective terminals from the body of enclosure 138. If enclosure 138 is formed from a non-conductive material, it may not be necessary to galvanically insulate the conductive portion of the power connectors from enclosure 138.

While separate insulating retainers 162 and 166 are shown, the skilled person will appreciate that a single insulating retainer may be used for insulating both positive terminal 164 and negative terminal 168 from enclosure 138.

One or more gaskets may be disposed between shelf 160 and the positive and negative power connectors 156 and 158. The (or each) gasket can individually or collectively have a first gasket aperture and a second gasket aperture through which the positive and negative power connectors 156 and 158 pass. The gasket(s) create a seal between enclosure 138 and positive and negative power connectors 156 and 158 respectively. The seal can be sufficient to prevent liquid ingress (e.g., from splashing or rain) and/or liquid egress (e.g., to ensure that any dielectric fluid within enclosure 138 cannot leak out).

As best shown in Figures 15 and 16, insulating retainer 166 includes a supporting lip 170 that extends beneath PCB 126 to provide vertical support to negative power pad 113. Supporting lip 170 assists during the wire bonding process described below, holding the power pads rigidly in a vertical direction and preventing excessive vibration under the force of a wire-bonding head when the wire bonds are being formed on the upper surface of negative power pad 113. Supporting lip 170 also galvanically isolates enclosure 138 from PCB 126. Insulating retainer 162 includes a corresponding supporting lip (not shown) that provides similar support and galvanic isolation to positive power pad 112.

Several wire bonds are formed between PCB 126 and other components of battery system 136. Wire bonding is a way of making electrical interconnections between components. A bonding head uses ultrasonic energy to create a bond between an aluminium or copper bond wire and a first surface. The wire is then drawn to a second surface and a second bond is made in a similar fashion. The bonding head then cuts the wire leaving behind a wire bond connection between the two surfaces.

Referring to Figure 14, each cell 150 has a single wire bond connection 172 from its positive cell terminal 152 to an adjacent cell-bonding pad 106 via through-hole 108, and a single wire bond connection 173 from its negative cell terminal 154 to an opposite adjacent cell-bonding pad 106 via through-hole 108. Since, in this implementation, there are two cells 150 exposed by each through-hole 108, there are two wire bond connections 172, 173 made to each cell bonding pad 106.

Each cell 150 is wire-bonded to its adjacent cell-bonding pads 106 in a similar fashion. In other implementations, different wire-bonding connection numbers and configuration can be used between cells and cell-bonding pads.

Although Figure 14 shows single wire bond connections 172, 173 between each cell terminal 152, 154 and adjacent cell-bonding pads 106, the skilled person will appreciate that one or more wire bond connections can extend from each cell terminal 152, 154 to one or more adjacent cell-bonding pads 106.

Also, although the through-hole 108 of Figure 14 exposes two cells 150 for wire bonding connection, the skilled person will appreciate that each through-hole 108 can be configured to expose only a single cell, or more than two cells.

Referring to Figure 15, negative terminal 168 of negative power connector 158 is wire-bonded to negative power pad 113 by way of several wire bond connections 174. Multiple wire bond connections 174 are used to meet the current capacity requirements of battery system 136. Similar wire bond connections (not shown) are used to wire- bond positive terminal 164 of positive power connector 156 to positive power pad 112.

The number and thickness of wire bond connections 174 can be selected such that they collectively act as an overcurrent fuse for the array of cells. If the current passing through wire bond connections 174 becomes excessive, at least one of wire bond connections 174 will melt and break. This will cause an increase in the average current passing through the remaining wire bond connections 174, causing the remaining wire bonds to melt and break, thereby disconnecting the array of cells and preventing an ongoing overcurrent fault.

Optionally, one or more of balancing resistors 132 are thermally connected to one or more of 150 cells, and the BMS is configured to provide for selective heating of the cells. Such thermal connection can be conductive and/or convective, for example. Optionally, a thermal transfer medium comprising a material having a high thermal conductivity relative to air can be used, in contact with one or more of the balancing resistors and one or more cell surfaces. Such a thermal transfer medium can be, for example, a solid, a liquid or a paste, preferably a non- electrically conductive or dielectric material.

Optionally, one or more of thermistors 130 are thermally connected to one or more of the cells, and, as for the balancing resistors, such thermal connection can include the use of a thermal transfer medium.

A gasket 182 is located between shelf 160 and the surface of populated 126 PCB surrounding signal connector 178. Gasket 182 has a gasket aperture 184 that matches the signal connector aperture 161 of shelf 160. Populated PCB 126 is positioned such that signal connector 178 passes through gasket aperture 182 and signal connector aperture 161. Screws 186 pull populated PCB 126 towards shelf 160. This urges a lower surface of PCB 126 into contact with an upper surface of gasket 182, which compresses gasket 182 such that it seals around signal connector 178. Due to signal connector 178 passing through gasket aperture 184 and signal connector aperture 161, it is accessible from outside enclosure 138. The seal can be sufficient to prevent liquid ingress (e.g., from splashing or rain) and/or liquid egress (e.g., to ensure that any dielectric fluid within enclosure 138 cannot leak out).

In other implementations, any suitable number of gaskets can be used for sealing signal connector 178, positive power connector 156, and negative power connector 158. A suitable aperture or apertures is provided for signal connector 178, positive power connector 156, and negative power connector 158. Optionally, one or more of signal connector 178, positive power connector 156, and negative power connector 158 can share an aperture.

In alternative implementations, signal connector 178 does not pass through gasket aperture 184 and/or signal connector aperture 161. In that case, a complementary connector (not shown) extends through gasket aperture 184 and/or signal connector aperture 161 to connect with signal connector 178.

Battery system 136 includes a lid (not shown) for sealing populated PCB 126 and cells 150 within enclosure 138.

In an alternative implementation shown in Figure 12, first enclosure aperture 198 and second enclosure aperture 200 are formed in a lid 176. First enclosure aperture 198 is positioned to expose a portion of positive terminal 164 and second enclosure aperture 200 is positioned to expose a portion of negative terminal 168. Gaskets (not shown) may be used to seal between lid 176 and positive and negative terminals 164, 168, similar to how gasket 182 seals around signal connector 178. In use, power connections (not shown) can be made to positive terminal 164 and negative terminal 168, while cells 150 and populated PCB 126 remain sealed within interior space 144.

The PCB described above provides a number of advantages, some of which are subtle but important.

One advantage of the described PCB is that it enables a particular assembly sequence that relies solely on top- down interactions. This enables top-down automated assembly to be employed, which can be cheaper and/or simpler than automated assembly approaches requiring more degrees of freedom. This is particularly the case when compared with using individual wires, which requires relatively high levels of dexterity, making it difficult to automate at a low cost.

The use of a PCB that allows for direct wire-bonding to an array of cells can result in a significantly reduced number of parts. For example, there is no need for separate wires and connectors from a busbar to a BMS for measuring voltage or temperature of cells.

The use of a PCB may also significantly reduce the number of assembly steps, because some or all interconnectors, components and connectors can be pre-integrated onto the PCB before assembly into an enclosure with a battery array. Depending upon the implementation, only the wire-bonded connections may need to be made during assembly. Where the PCB includes intermediate layers, these can be used to shield signal- carrying traces from electromagnetic interference, which can result in reduced noise and increased measurement accuracy. Shielding is more challenging when wires are used.

The use of a PCB that at least partly covers the array of cells may allow BMS components, such as such as temperature sensors, signal filtering and amplifying components, balancing components and (power) switching components, to be positioned closer to the cells, resulting in improved sensing accuracy, improved thermal management and/or a more compact battery system.

Referring to Figure 23, there is shown a method 202 of assembling a battery system. The battery system can be, for example, of the type that incorporates a PCB as described above and defined in the claims.

An array of cells, such as cells 150, is disposed 204 within an enclosure, such as enclosure 138. Optionally, the enclosure can include scaffolding, formwork, or other formations or structures that do one or more of holding the cells in position within the enclosure, insulating the cells from each other and/or the enclosure, channelling coolant fluid past the cells, and providing attachment points to which components can be attached, as described elsewhere.

A PCB, such as populated PCB 126, is lowered 206 into position above the array of cells. In this position, the PCB can cover some or all of the upper surface of the array.

The PCB is then optionally fastened to the enclosure. Fastening can be done using any suitable fastening method or technique, including, but not limited to, screws, clips, rivets, nuts, bolts and adhesives. The fastening may be to the enclosure directly, or to any scaffolding or support structure within the enclosure, such as scaffolding for the battery array.

Wire-bonded connections are then made 210 between the cell terminals and cell-bonding pads on the PCB, for example as described above.

Optionally, the PCB comprises a signal connector extending from one side, such as the signal connector 178 described above. In that case, the method can comprise lowering the PCB into position such that the signal connector passes through an aperture, such as signal connector aperture 161, on a shelf of the enclosure. The PCB is connected to the shelf so as to compress a gasket, such as gasket 182, between the shelf and the PCB, thereby creating a seal between the signal connector and the enclosure.

Where a gasket is used, it can comprise an aperture, such as gasket aperture 184. In that case, the method can comprise, prior to lowering the PCB into position, placing the gasket onto the shelf such that the aperture in the gasket is aligned with the aperture in the shelf. Alternatively, the gasket can be placed over the signal connector before the PCB is lowered into position, as shown in Figure 8.

Optionally, prior to lowering the PCB into position, positive and negative power connectors, such as positive and negative power connectors 156 and 158, are lowered into the enclosure. The positive and negative power connectors are positioned such that, when the PCB has been lowered into position, the positive connector is positioned adjacent one of the power pads and the negative connector is positioned adjacent the other of the power pads.

Optionally, the power connectors may pass through apertures in the enclosure. In that case, the method can comprise lowering the power connectors into position such that the power connectors pass through one or more apertures, such as enclosure apertures 191 and 193, on one or more shelves of the enclosure. The power connectors are fixed to the shelf or shelves so as to compress one or more gaskets thereby creating a seal between the power connectors and the enclosure.

If one or more gaskets or seals are used, for example as described above, they are positioned at a suitable time in the assembly process. Wire-bonded connections between the power connectors and the corresponding power pads can then be made, for example as described above.

Turning to Figures 19 to 22, there is shown a PCB 212. In one implementation, PCB 212 can be a PCB such as any of the implementations described above, and/or as defined by the claims. Alternatively, PCB 212 can be for a different circuit or circuits, which can be for a different application to that described above. There are, however, additional advantages that arise when the PCB is used (or usable) in at least two different but related products, and where the connectors on those different products need to be located on different surfaces of the products' respective enclosures. Rechargeable batteries with two or more different configurations, using the same PCB but having connectors on opposite sides of the PCB, is one non-limiting example of such related products.

PCB 212 includes a substrate 214, which can be, for example, substrate 102 of any of the implementations described above, and/or as defined by the claims. However, substrate 214 can take any other suitable form, depending upon the intended application of PCB 212.

Substrate 214 includes a first side 218. First side 218 comprises first connector mounting pads 220 to which a first connector 221 can be mounted, as described in more detail below. First side 218 also includes a first gasket sealing surface 222 surrounding first connector mounting pads 220. First gasket sealing surface 222 can be relatively smooth, and free of, for example, holes or other features that might prevent a gasket from forming a seal.

Substrate 214 includes a second side 224 opposite first side 218. Second side 224 comprises second connector mounting pads 226 to which a second connector 227 can be mounted, as described in more detail below. Second side 224 also includes a second gasket sealing surface 228 surrounding second connector mounting pads 226. Second gasket sealing surface 228 is relatively smooth, and free of, for example, any features that might prevent a gasket from forming a seal.

First and second connector mounting pads 220, 226 have at least some conductive connections to PCB 212 in common. Conductive connections can include, for example, conductive traces formed on one or both surfaces of PCB 212, and/or any internal traces when PCB 212 is a multilayer PCB. By having at least some conductive connections in common, a first connector 221 or a second connector 227 can be mounted to the respective first and second connector mounting pads 220, 226, depending upon the use to which the PCB is to be put.

An exception to avoiding any features within first gasket sealing surface 222 and second gasket sealing surface 228 is screw holes 229, which allow screws (not shown) to pass through PCB 212. As with screws 186 in Figure 11, for example, such screws can be used to pull PCB 212 towards a further sealing surface, formed, for example, on an inner surface of an enclosure or lid. The surface of shelf 160 is an example of such a further sealing surface. A gasket between the first or second sealing surface 222, 228 and the further sealing surface is compressed, causing a seal around the corresponding first or second connector 221, 227. Alternatively, some of all of screw holes 229 can be positioned inside or outside first or second sealing surfaces 222, 228.

In some implementations, first and second connector mounting pads 220, 226 have exactly the same combination of conductive connections to the PCB 212. This enables the first and second connectors 221, 227 to have the same functionality, irrespective of which is used with PCB 212. Optionally, first and second connector mounting pads 220, 226 also have the same layout and electrical connection configuration as each other, enabling the use of the same connector type for both the first and second connectors 221, 227.

In use, a decision is made as to whether first or second connector mounting pads 220, 226 are to be used for a particular application. For example, if PCB 212 is to be installed in a product that requires a connector on first side 218, then first connector 221 is mounted to first connector mounting pads 220. Alternatively, if PCB 212 is to be installed in a related product that requires a connector on second side 224, then second connector 227 is mounted to second connector mounting pads 226.

The mounting can take any suitable form, such as soldering, wire-bonding, or other forms of conductive connection. First and second connectors 221, 227 can be, for example, surface mount or through-hole connectors that are soldered directly to conductive traces carrying power and/or signals. Optionally, the mounting can include attaching the first or second connector 221, 227 to PCB 212 at a point that is not connected to any circuitry carried by PCB 212, such as a pad that is not connected to any other circuitry, or is merely grounded.

In general, PCB 212 and first and second connector mounting pads 220, 226 are configured such that a connector is only mounted to one or the other of first and second connector mounting pads 220, 226. It is possible, however, to have connectors mounted to both first and second connector mounting pads 220, 226.

First and second connectors 221, 227 can be for transferring power and/or signals between PCB 212 and another component or system. As an example, rechargeable batteries can have various types of connector arrangements that make power and/or data connections when the battery is connected to a device it is intended to power. First and second connectors 221, 227 can include contacts (not shown) that enable such connections to be made when the product into which PCB 212 is installed is connected to the device it is intended to power. Optionally, first and second connector mounting pads 220, 226 are coincident with each other on PCB 212. That is, the areas of first and second connector mounting pads 220, 226 at least partly overlap each other. This allows for shorter routing of conductive connections to first and second connector mounting pads 220, 226.

PCB design and production can be expensive. This is particularly the case for complex PCBs, especially where multiple layers are involved. Producing smaller numbers of PCBs can also add to costs, because, in general, the unit rate for PCBs falls as the number of PCBs produced or ordered rises. Providing connector mounting pads on opposite sides of PCB 212 allows for a single PCB 212 to be used for multiple implementations with different connector requirements.

The use of gasket sealing surfaces on both sides of PCB 212 further increases the flexibility of PCB 212.

Referring to Figure 24a, there is shown an implementation in which a coolant is used for thermal management of cells 150. For example, the coolant can take the form of a dielectric fluid and can be used for cooling cells 150, equalising the temperature of cells 150, and/or heating cells 150, as required by the implementation and current circumstances (such as ambient temperature, airflow, and power requirements). The dielectric fluid can be pumped around the cells by a pump (not shown) as described below. Alternatively, the dielectric fluid can move around the cells due to convection, such that as the dielectric fluid is heated by the cells, it moves up and is replaced by cooler fluid from below (the reverse can happen if the cells are being heated by the dielectric fluid).

To this end, a scaffolding 501 is provided, to be disposed within an enclosure (such as enclosure 138). In the illustrated implementation, the scaffolding is comprised of a lower part 501-1 and an upper part 501-2 as shown in Figures 24c and 24e. The lower part 501-1 comprises dividers that define separate scaffolding channels 512-1 ... 512-5 in the battery system. As shown in Figure 24b, the lower part of the scaffolding, and in particular the channels of the lower part, may further comprise cell receptacles 514 in which the battery cells can be placed. The use of such a scaffolding simplifies the manufacturing of the battery system and ensures correct placement of the battery cells.

Figures 24c and 24d show the lower part of the scaffolding 501-1 from a perspective view before and after the battery cells are located in the cell receptacles 514.

Exemplary flows across the channels 512-1 ... 512-5 of the scaffolding are shown in Figure 24a. As shown in this figure, typically the battery system is arranged so that the direction of flow in each of the channels is the same, from a first side of the enclosure to a second side of the enclosure.

In order to assemble the battery system, cells are first lowered into the cell receptacles 514 of the lower part of the scaffolding as shown in Figure 24d. PCB 126 is then lowered into place on top of the scaffolding, as shown in plan form in Figure 25. For clarity, PCB 126 is shown in Figure 25 in outline only, with its physical features removed to enable visibility of temperature sensors and heating elements, as described in more detail below. In addition, the skilled person will appreciate that the configuration of enclosure 138 will be modified slightly for use with the scaffolding of Figures 24a-24d.

Optionally, the upper part of the scaffolding 501-2 is positioned underneath PCB 126 and may include channel dividers and/or cell receptacles that align with the channel dividers and the cell receptacles of the lower part so that the lower part of the scaffolding 501-1 and the upper part of the scaffolding cooperate to form the channels and the cell receptacles.

The battery cells in the scaffolding 501 are typically arranged so that the coolant flows transversely across the cells, as shown in Figure 24a.

In order to allow the flow of coolant in/out the channels in the scaffolding from/to other sections of the battery system, PCB 126 can comprise transfer holes (not shown). The transfer holes can be arranged along a first side and a second side of the PCB to align with the entry and exit locations of the coolant as it flows through each of the channels in the scaffolding. In some embodiments, instead of holes, the PCB comprises cut-outs (e.g. one cut out for each location where the coolant enters a channel and one cut-out for each location where coolant exits a channel) that enable the coolant to flow between the PCB and the inside of the enclosure of the battery system.

In some implementations, the battery system comprises temperature sensors 552 and/or pressure sensors. These can optionally be associated with the fluid channels. For example, each channel may be associated with one or more temperature sensors arranged to determine a temperature of the coolant in that channel. This may comprise the battery having a temperature sensor at one or more of the ends of each channel (e.g. at the entrance and/or the exit of one or more channels).

Temperature sensors 552 can optionally be mounted to PCB 126. In the implementation of Figure 25, temperature sensors 552 (shown as squares drawn with dashed lines) are mounted to corresponding mounting pads on an underside of PCB 126. This places them closer to cells 150. Optionally, sensors 552 are arranged such that they are in direct contact with the dielectric fluid, which improves thermal transfer and therefore the responsiveness of the temperature sensors 552 to temperature change.

Typically, there is greater variation of temperature between the exits of the channels than between the entries of the channels. Therefore, there may be more temperature sensors 552 provided at the exits of the channels than at the entrances so that there is a greater sensing resolution at the exits of the channels. In Figure 25, for example, there is one temperature sensor 552 for each exit, but only two temperature sensors 552 in two of the five entrances. Any suitable number of temperature sensors 552 may be provided at any suitable position(s) within the fluid channels (or anywhere else in thermal proximity to the cells, if channels are not used).

The temperature sensors may be used to determine a temperature distribution at the entrances and/or exits of the channels. This distribution is useable to identify a damaged cell (e.g. if one channel does not fit neatly into the distribution) and is also useable to identify trends in the heating of the cells. For example, the distribution may show that the outer channels are cooler than the inner channels, and this may result in additional coolant being diverted to the inner channels.

In some embodiments, the battery system comprises flow rate sensors (not shown) in one or more of the channels of the battery cell layers, the channels of the end plates, and a pump (not shown). As with the temperature sensors, flow rate sensors can be used to identify potential faults in the battery system. In particular, flow rate sensors can be used to identify sub-optimal flow of coolant through a channel. The operation of the battery system can then be altered accordingly (e.g. to divert more coolant through this channel).

The temperature sensors are typically arranged to measure the temperature of the coolant in each channel. By combining the temperature measurements with the flow rates of the channels, the temperatures of each of the cells (or each sub-group of cells) can be estimated. This enables the operation of a pump (not shown) and/or the operation of the battery cells to be altered to ensure that the temperature of each battery cell is within a desired range. In particular, if the cells are becoming undesirably hot, additional power may be provided to the pump to increase the rate of flow of coolant through the battery system and/or less current may be drawn from the battery cells to reduce the rate of heating. The pump and/or the battery cells are typically arranged to operate in dependence on the measurements taken by the temperature sensors. This may comprise the temperature sensors providing these measurements to a control module that controls the pump and the battery cells.

The operation of the battery cells is typically dependent on the temperature of these cells, where the battery cells have a maximum optimal operating temperature. Therefore, the coolant is used to transfer heat away from the battery cells to the surroundings of the battery in order to avoid overheating. As well as having a maximum optimal operating temperature, the battery cells may have a minimum optimal operating temperature. Therefore, as shown in Figure 25, one or more heating elements 554 (shown as circles drawn with solid lines) may be provided in the battery system in order to transfer heat to the battery cells. These heating elements are usually activated at the start of the operation of the battery system (e.g. when a user first starts the vehicle).

Specifically, the battery system may comprise a plurality of heating elements 554 distributed across the battery system. In the implementation of Figure 25, heating elements 554 are mounted to corresponding mounting pads on the top side of PCB 126. Optionally, heating elements 554 are arranged such that they are in direct contact with the dielectric fluid, which improves thermal transfer.

In one implementation, balancing resistors (such as balancing resistors 132 described above) can serve a dual purpose by acting as heating elements. This is achieved by driving the balancing resistors with a suitable drive current, under the control of the BMS, when they are not being used for balancing purposes. Additional separate heating elements may still be included, if the balancing resistors are not capable of providing sufficient heating power by themselves

The heating elements are typically distributed across the PCB so there may, for example, be one or more heating elements (or balancing resistors) located between a plurality of cells or between each pair of cells. Providing distributed heating elements rather than a single heating element can lead to more uniform heating throughout the battery system and so avoids undesirable hotspots and related safety risks. The use of a dielectric coolant enables the heating elements 554 to warm the coolant and thereby warm the battery cells whilst being mounted on the PCB.

"Cells", in the context of the present application, includes battery cells, whether rechargeable or not, and other forms of energy storage devices that output electrical power and may be arranged in an array, including, for example, capacitors and supercapacitors.

Similarly, "BMS" is intended to include any circuit suitable for managing and/or monitoring the type of energy storage devices with which the PCB is to be used.

Directional references, such as "upper" and "lower", are for convenience of description. While certain advantages may apply when the described components are used with such orientations, in the broadest form, the invention and its various aspects are not limited to particular orientations.

The drawings are schematic, and do not show details such as, for example, individual mounting pads for all terminals of components that are to be mounted to such pads. Similarly, various components, such as thermistors, switches, balancing resistors, and the like, are shown schematically.

Although the invention has been described reference to a number of specific non-exhaustive and non-limiting examples, the skilled person will appreciate that the invention may be embodied in many other forms.

Claims

1. A battery system comprising: an enclosure; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; a coolant comprising a dielectric fluid that is electrically non-conductive; and a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell bonding pads; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; wherein: the cell terminals on the top surface of the cells are wire-bonded to corresponding cell-bonding pads on the PCB through the through-holes; at least a part of an outer surface of one or more cells and at least some of the electronic components are in direct contact with the coolant when the battery system is in use; and the coolant enables the transfer of heat from one or more of the cells to one or more of the electronic components and vice versa.

2. The battery system of claim 1, wherein the PCB comprises a further conductive layer on an opposite side of the substrate from the first conductive layer, wherein one or more of the electronic components are mounted to mounting pads on the further conductive layer.

3. The battery system of any preceding claim, wherein the electronic components installed onto the mounting pads on the PCB comprise heating elements for heating the coolant.

4. The battery system of claim 3, wherein the heating elements are balancing resistors for use in balancing voltages of the cells.

5 The battery system of claim 4, comprising at least 10 of the heating elements, at least 25 of the heating elements, at least 50 of the heating elements, or at least 100 of the heating elements.

6. The battery system of any preceding claim, wherein the electronic components installed onto the mounting pads on the PCB comprise cooling elements for cooling the coolant.

7. The battery system of any preceding claim, wherein the heating and/or cooling elements are mounted in a region of the PCB above the array of cells.

8. The battery system of any preceding claim, wherein the heating and/or cooling elements are mounted in a region of the PCB within which the cell-bonding pads are located.

9. The battery system of any preceding claim, wherein the heating and/or cooling elements are distributed so as to provide even heating and/or cooling of the array of cells.

10. The battery system of any preceding claim, wherein the electronic components installed onto the mounting pads on the PCB comprise temperature sensors for providing signals to a battery management and/or monitoring system (BMS).

11. The battery system of claim 10, wherein at least some the electronic components installed onto the mounting pads on the PCB together comprise a BMS.

12. The battery system of any preceding claim, wherein the enclosure comprises a scaffolding that locates the array of cells and provides a flow path for the coolant so that the coolant can pass across the cells when the battery system is in use.

13. The battery system of claim 12, wherein the scaffolding comprises a plurality of channels, wherein each channel is arranged to provide a flow path for the coolant so that the coolant passes across the cells, preferably wherein each scaffolding comprises at least three channels, at least six channels, and/or at least ten channels.

14. The battery system of claim 13, wherein the PCB comprises transfer holes/cut-outs, arranged to align with the channels of the scaffolding, such that the coolant enters the channels of the scaffolding and/or leaves the channels of the scaffolding by passing through the transfer holes/cut-outs of the PCB.

15. The battery system of claim 13 or 14, wherein one or more temperature sensors are mounted on the PCB adjacent one or more exits through which the coolant leaves the channels of the scaffolding.

16. The battery system of any one of claims 13 to 15, wherein one or more temperature sensors are mounted on the PCB adjacent one or more entrances through which the coolant enters the channels of the scaffolding.

17. The battery system of claim 16 when dependent upon claim 15, comprising a plurality of the temperature sensors mounted adjacent the exits, and one or more temperature sensors mounted adjacent the entrances, wherein the number of temperature sensors located at the exits is greater than the number of temperature sensors located at the entries.

18. The battery system of any of claims 15 to 17, wherein the temperature sensors are arranged to: determine a faulty battery cell; and/or determine a temperature distribution in the coolant; and/or control the operation of one or more cells, preferably in dependence on the temperature distribution in the coolant; and/or determine a temperature of a cell based on a temperature of the coolant; and/or control the operation of a pump, preferably in dependence on the temperature distribution in the coolant.

19. The battery system of claim 3 or 6, or of any claim dependent upon claim 3 or 6, wherein the heating and/or cooling elements are arranged to operate in dependence on a/the temperature sensor(s) in the battery system.

20. The battery system of any preceding claim, wherein the electronic components installed onto the mounting pads of the PCB collectively perform some or all the functions of a battery monitoring and/or management system (BMS).

21. A battery system comprising: an enclosure; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell bonding pads, wherein the cell terminals on the top surface of the cells are wire-bonded to corresponding cell-bonding pads on the PCB through the through-holes; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; a positive power connector, wherein a top surface of the positive power connector is internal to the enclosure and positioned adjacent to the positive power pad, and is wire-bonded to the positive power pad of the PCB; and a negative power connector, wherein a top surface of the negative power connector is internal to the enclosure and positioned adjacent to the negative power pad, and is wire-bonded to the negative power pad of the PCB.

22. The battery system of claim 21, wherein: the enclosure comprises a first enclosure aperture and a second enclosure aperture; the positive power connector electrically couples the inside of the enclosure to the outside of the enclosure through the first enclosure aperture, such that the positive power connector is electrically accessible from outside of the enclosure; and the negative power connector electrically couples the inside of the enclosure to the outside of the enclosure through the second enclosure aperture, such that the negative power connector is electrically accessible from outside of the enclosure.

23. The battery system of claim 22, wherein each of the positive power connector and the negative power connector comprises a solid block formed from a conductor, the solid blocks being: exposed within the enclosure; and exposed outside the enclosure on the other sides of their respective enclosure apertures.

24. The battery system of claim 22 or 23, wherein the enclosure comprises one or more internal shelves on which the first and second enclosure apertures are located.

25. The battery system of claim 24, comprising one or more gaskets between the one or more shelves and the positive and negative power connectors, wherein the one or more gaskets comprise one or more gasket apertures through which the positive and negative power connectors pass, the one or more gaskets creating a seal between the enclosure and the positive and negative connectors respectively.

26. The battery system of any one of claims 21 to 25, wherein the positive and negative power connectors comprise an insulating retainer to galvanically isolate conductive portions of the respective power connectors from the enclosure.

27. The battery system of claim 26, wherein the or each insulating retainer comprises a supporting lip extending under the corresponding power pad on the PCB, the supporting lip being configured to galvanically isolate the enclosure from the PCB.

28. The battery system of claim 26, wherein the insulating retainer comprises a supporting lip extending under the corresponding power pad on the PCB, the supporting lip being configured to support the PCB whilst the wire-bonds are being formed between the power connector and power pad.

29. The battery system of any one of claims 21 to 28, wherein the positive and negative power pads are both disposed at a same edge of the PCB.

30. The battery system of any one of claims 21 to 29, wherein: the array of cells defines a first sub-array corresponding to a first side of the PCB in plan, and a second sub-array corresponding to a second side of the PCB in plan, the second side being opposite the first side, the first sub-array and second sub-array comprising an equal number of cells; the power circuit comprises a first conductive path extending through the first side and the first sub array, and a second conductive path extending through the second side and the second sub-array, the first and second conductive paths being joined at an edge of the PCB opposite to the edge upon which the positive and negative power pads are disposed; configured such that current flows from the positive power pad through the first conductive path in a first direction, and then through the second conductive path to the negative power pad in a second direction substantially opposite to the first direction.

31. The battery system of claim 30, comprising a third conductive path joining the first and second conductive paths, configured such that current flows through the third conductive path in a direction generally normal to the first and second directions.

32. The battery system of any one of claims 21 to 31, where dependent on claim 29, wherein: the electronic components comprise one or more switching components for selectively opening and closing the power circuit; and the switching component(s) are disposed at an opposite edge of the BMS to the positive and negative power pads.

33. The battery system of claim 32, wherein the switching component(s) are positioned at a mid-point of the power circuit.

34. The battery system of any one of claims 21 to 33, wherein the number of wire bonds between each power connector and its corresponding power pad is selected such that in the event of an over-current situation, the wire bonds will act as a fuse and melt.

35. The battery system of any one of claims 21 to 34, wherein the electronic components installed onto the mounting pads of the PCB collectively perform some or all the functions of a battery monitoring and/or management system (BMS).

36. A method of assembling the battery system of any one of claims 21 to 35, comprising: lowering the positive and negative power connectors into the enclosure; lowering the PCB into position above the array of cells, such that the positive connector is positioned adjacent to the positive power pad and the negative connector is positioned adjacent to the negative power pad; and making wire-bonded connections between the cell terminals and the cell-bonding pads, and between the top surfaces of the power connectors and the corresponding power pads.

37. The method of claim 36, for the battery system dependent on claim 5 comprising: prior to lowering the positive and negative power connectors into the enclosure, placing the one or more gaskets onto the one or more shelves such that the gasket apertures are aligned with the first and second enclosure apertures; and fixing the power connectors to the enclosure so as to compress the one or more gaskets between the one or more shelves and the power connectors, thereby sealing the first and second enclosure apertures.

38. The method of claim 36 or 37, comprising fastening the PCB to the enclosure prior to making wire- bonded connections between the cell terminals and the cell-bonding pads.

39. A battery system comprising: an enclosure comprising a signal connector aperture; an array of vertically orientated cells held within the enclosure, wherein each cell has at least one cell terminal at its top surface; and a printed circuit board (PCB) installed over the array of cells, the PCB comprising: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell bonding pads, wherein the cell terminals on the top surface of the cells are wire-bonded to corresponding cell-bonding pads on the PCB through the through-holes; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use; wherein the electronic components comprise a signal connector for transferring signals to and from the other electronic components, the signal connector passing through the signal connector aperture such that the signal connector is directly accessible from outside of the enclosure.

40. The battery system of claim 39, wherein the PCB comprises a further conductive layer on an opposite side of the substrate from the first conductive layer, wherein the further conductive layer comprises one or more of the mounting pads and wherein the signal connector is mounted on one of the mounting pads on the further conductive layer.

41 The battery system of claim 39 or 40, wherein the enclosure comprises a shelf through which the signal connector aperture passes.

42. The battery system of claim 41, comprising a gasket between the shelf and the PCB, wherein the gasket has a gasket aperture through which the signal connector passes, the gasket creating a seal between the signal connector and the enclosure.

43. The battery system of any one of claims 39 to 42, wherein the electronic components installed onto the mounting pads of the PCB collectively perform some or all the functions of a battery monitoring and/or management system (BMS).

44. A method of assembling the battery system of any one of claims 39 to 43, comprising: disposing the array of cells within the enclosure; lowering the PCB into position above the array of cells such that the signal connector passes through the signal connector aperture; fastening the PCB to the enclosure; and making wire-bonded connections between the cell terminals and the cell-bonding pads.

45. The method of claim 44, when used to assemble the battery system of claim 42 or 43, comprising: prior to lowering the PCB into position, placing the gasket onto the shelf such that the gasket aperture is aligned with the signal connector aperture; and fixing the PCB to the enclosure so as to compress the gasket between the shelf and the PCB, thereby sealing the signal connector aperture.

46. The method of claim 44, when used to assemble the battery system of claims 42 or 43, comprising: prior to lowering the PCB into position, placing the gasket onto the PCB such that the gasket surrounds the signal connector; and fixing the PCB to the enclosure so as to compress the gasket between the shelf and the PCB, thereby sealing the signal connector aperture.

47. A PCB, the PCB comprising: a substrate; a first side, the first side comprising first connector mounting pads to which a first connector can be mounted; and a second side opposite the first side, the second side comprising second connector mounting pads to which a second connector can be mounted; the first and second connector mounting pads having at least one conductive connection to the PCB in common, such that the first connector or the second connector can be mounted to the respective first and second connector mounting pads, depending upon the use to which the PCB is to be put.

48. The PCB of claim 47, wherein the first and second connector mounting pads have the same conductive connections to the PCB.

49. The PCB of claim 47 or 48, wherein the first and second connector mounting pads are coincident with each other.

50. The PCB of any one of claims 47 to 49, comprising: a first gasket sealing surface surrounding the first connector mounting pads; and a second gasket sealing surface surrounding the second connector mounting pads.

51. The PCB of any one of claims 47 to 50, wherein the PCB comprises: a substrate; a first conductive layer disposed on a side of the substrate that is opposite the array of cells, the first conductive layer comprising a plurality of cell-bonding pads; an array of through-holes, each of the through-holes being adjacent to at least one of the cell-bonding pads; positive and negative power pads that are conductively coupled to the cell-bonding pads, to create a power circuit that allows for the transfer of power to and from the array of cells; and mounting pads, to at least some of which are installed electronic components that allow for monitoring and/or management of the cells when the battery system is in use.

52. The battery system of any one of claims 1 to 35 or 39 to 43, comprising the PCB of any one of claims 47 to 51.

53. The PCB of any one of claims 47 to 52, for use in at least first and second related products, wherein the first product uses a first connector mounted to the first connector mounting pads, and the second product uses a second connector mounted to the second connector mounting pads.

54. A first product comprising the PCB of any one of claims 47 to 53 and a second product comprising the PCB of any one of claims 47 to 53, wherein: the PCB of the first product comprises a first connector mounted to the first connector mounting pads; and the PCB of the second product comprises a second connector mounted to the second connector mounting pads.