GB2364452A

GB2364452A - Auxiliary battery control for a starter motor

Info

Publication number: GB2364452A
Application number: GB0016462A
Authority: GB
Inventors: Arnot Lindsey Franses
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-07-04
Filing date: 2000-07-04
Publication date: 2002-01-23
Anticipated expiration: 2020-07-04
Also published as: AU2001267736A1; WO2002007286A8; GB2364452B; WO2002007286A1; GB0016462D0

Abstract

A motor installation comprises, a first battery (1), a second battery (2), first and second switches (3a, 3b), a starter motor (4), and a high current switch (6). The first battery has an earth terminal connected to the installation earth. The high current switch connects the earth terminal of the second battery to the installation earth. The positive terminals of the batteries are connected by a common positive line. Operation of the first switch closes the high current switch, thus connecting the batteries in parallel. The second switch operates the starting motor. The second switch may be inhibited from closing until the first switch has been operated. The first and second switches may comprises respective poles of a rotary multipole switch e.g. an ignition switch. A timer circuit (8) may be provided to re-open the high current switch after a predetermined time. A voltage sensing circuit may be provided to sense the voltage when the voltage across the first battery reaches a predetermined level and close the high current switch to charge the second battery. The system may be provided in kit form. An electrode plate for a lead acid battery comprising an apertured frame is also disclosed.

Description

2364452 Starting Motors

Description

The present invention relates to starting motors.

Motor vehicles, including cars, vans, lorries, boats and aircraft, and other motor installations such as electric generators are typically driven by internal combustion engines. Such engines need to be driven through their cycles by an external power source for starting and an electric starter motor is usually provided for this.

Starter motors are themselves usually powered from a battery in the vehicle which is re-charged by an generator driven by the vehicle's engine. However, these batteries are also used for powering auxiliary apparatus, e.g. lights, air-conditioning systems and entertainment systems, and hotel loads. The use of the auxiliary apparatus 15 while the vehicle's engine is not running and the powering of the hotel loads can lead to the battery becoming fully discharged. If this occurs, the engine cannot be restarted.

The lead-acid accumulators commonly used in road vehicles also slowly discharge 20 when not being used. Consequently, the user of a vehicle may be confronted with the problem of starting the vehicle after a period of non- use during which the battery has become discharged. Furthermore, emergency service vehicles often carry a large number of electrical loads, including lights, sirens and communications equipment, and on occasion the battery has been found to run down while a 25 vehicle's engine is running.

Many solutions to this problem, using additional batteries, have been proposed, see for example EP-A-0 838 888.

30 According to the present invention, there is provided a motor installation comprising a starter motor, a first battery having an earth terminal coupled to the vehicle earth, a second battery, first switch means, second switch means for initiating operation of the starter motor, a controllable high-current switch means Case: 34\732 for selectively electrically coupling the earth terminals of the first and second batteries and control means, the non-earth terminals of the batteries being connected together, wherein the control means is configured to be responsive to operation of the first switch means to close the high-current switch means thereby 5 coupling the earth terminals of the batteries. The first and second switch means may be different poles of a multipole rotary switch. Preferably, the second switch cannot be operated to start the engine before the first switch has been operated to connected the earths of the batteries.

lo According to the present invention, there is also provided the kit comprising said second battery, said high-current switch means and said control means, the control means having an input and an output and being configured such that, when operational, the output changes to produce a signal for closing the high- current controlled switching means when a signal at the input undergoes a predetermined 15 change.

The controllable high-current switch means is preferably one or more solid-state devices, such as MOSFETs. However, an electromechanical switch, e.g. a relay, could be used.

Preferably, the control means includes a timer circuit for causing the high-current switch means to reopen when a predetermined period has elapsed since operation of the starter switch for starting. The timer circuit need not force re- opening of the high-current switch, if some other criterion for keeping the switched closed 25 continues to be met. For instance, voltage sensing means is preferably included for sensing the voltage across the first battery and the control means is responsive to the voltage sensing means to close said high-current switch means when the voltage sensed by the voltage sensing means exceeds a predetermined voltage. Thus, the second battery can be charged when sufficient energy is available.

Preferably, the control means is powered from the second battery when the high current switch means is open. Consequently, if the second battery is flat or has been removed, the vehicle can be operated in the conventional single- battery manner without an special operations being required.

According to the present invention, there is further provided an electrode plate for 5 a lead acid battery comprising an apertured frame and a terminal portion on the frame, wherein the cross-sectional areas of frame portions between apertures remote from the terminal portion are less than those near the terminal portion. The apertures may be rectangular, circular or any other shape. The apertures are preferably arranged in rows and columns.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a functional block diagram of a system according to the present invention; 15 Figure 2 is a circuit diagram of the system shown in Figure 1; Figure 3 is a plot illustrating the operation of the comparator of Figure 1; and Figure 4 shows a plate of a battery.

Referring to Figure 1, the starting arrangements for an internal combustion engine 20 (not shown) of a motor vehicle comprise a first battery 1, a second battery 2, an ignition switch unit 3a, 3b, a starter motor 4. a relay 5, a high-current solid-state switch 6, e.g. intelligent MOSFETs having internal thermal and overcurrent protection, a comparator 7, a timer 8 and an OR-ing circuit 9. The ignition switch unit is a three position rotary switch (more positions may be provided) having first 25 and second poles 3a, 3b. The ignition switch is also sprung so that it returns to the second position from the third position unless held there by a user.

The second battery 2 is preferably one adapted for supplying large currents, such as a Hawker SBS40.

The positive terminals of the batteries 1, 2 are connected together by a common positive line. The negative terminal of the first battery 1 is connected directly to the vehicle earth and the negative terminal of the second battery 2 is connected to the solid-state switch 6 which can be turned on to connect the negative terminal of the second battery to the vehicle earth.

The first pole 3a of the ignition switch and the relay 5 are connected such that when 5 the ignition switch 3a, 3b is in its second position, current flows from the common positive line through the first pole 3a of the ignition switch and then through the coil of the relay 5 to earth. When current flows through the coil of the relay 5, the relay 5 closes energising the starter motor 4 from the common positive line.

lo The timer 8 is connected between the second pole 3b of the ignition switch and one input of the OR-ing circuit 9. The other input of the ORing circuit 9 is connected to the output of the comparator 7. One input of the comparator 7 is connected to the common positive line and the other is connected to a reference voltage (Vref). The comparator 7 exhibits hysteresis. The output of the OR-Ing circuit 9 is 15 connected to the control terminal of the solid-state switch 6.

If the voltage across the first battery 1 is greater than a first threshold, e.g. 13.2V, the comparator 7 produces an output that causes the OR-Ing circuit 9 to close the solid-state switch 6. This connects the second battery 2 in parallel with the first 2o battery 1 so that the second battery 2 can charge.

If the voltage on the common positive line now falls, due to discharging or instantaneous current demand, to below a second threshold, for example, 12.8V, the output of the comparator 7 changes state causing the solidstate switch 6 to open.

25 This isolates the earth terminal of the second battery 2 from the vehicle earth and prevents it being undesirably discharged.

When a user comes to start the vehicle, the user turns the ignition switch 3a, 3b initially to its first position. This causes the timer 8 to produce an output for the 30 predetermined period which is applied to an input of the OR-ing circuit 9. This causes the OR-ing circuit 9 to close the solid-state switch 6.

The user can now turn the ignition switch 3a, 3b to its third position. The output of the second pole A remains unchanged. However, the first pole 3 a now connects the coil of the relay 5 to the common positive line. In this configuration and assuming that the timer 8 has not timed out, the second battery 2 is available to 5 supply current to the starter motor 4 for starting the vehicle's engine.

When the period of the timer 8 expires, its output returns to its original state. If the voltage on the common positive line is now above the first threshold, for example because the vehicle's engine is running and its generator is only lightly loaded, the 10 solid-state switch 6 is kept closed by the action of the comparator 7. However, if the voltage on the common positive line is not above the first threshold, for example because the engine has not started or the engine is running with the generator heavily loaded, the solid-state switch 6 opens when the output of the timer 8 returns to its original state.

The timer 8 ensures that the second battery 2 is connected in circuit until any engine management electronics have been initialised, any preheat circuits operated (diesels), the engine has started and the generator output stabilised.

20 While the engine is running, at any time when the voltage on the common positive line exceeds the first threshold, the solid-state switch 6 will be closed for recharging of the second battery 2 by the action of the comparator 7 until the voltage on the common positive line falls below the second threshold.

25 Referring to Figure 2, the comparator 7, the timer 8 and the OR-Ing circuit 9 are implemented using a MAX951 combined operational amplifier 11 and comparator 12 integrated circuit and supporting passive components. The integrated comparator 12 is inherently hysteretic.

30 The MAX951 is powered from the second battery 2 and the integrated comparator 12 includes a reference voltage generator (not shown) that produces a reference voltage of 1.2V above, in this case, the negative terminal voltage of the second battery 2. The reference voltage is available at the inverting input (-) of the integrated comparator 12 and is supplied to the non-inverting input of the operational amplifier 11 via a first resistor 10.

The circuit in Figure 2 will be better understood, if it is borne in mind that the 5 reference voltage (Vref) produced in the integrated comparator 12 is (V1 - V2) + 1.2, where V1 is the voltage across the first battery 1 and V2 is the voltage across the second battery 2. Thus, as the voltage across the first battery 1 increases, the reference voltage rises in sympathy.

10 The comparator 7 in Figure I is provided by the operational amplifier 11, which has a gain of about 10, and a potential divider for sensing the voltage across the first battery 1. The potential divider comprises a larger resistor 13 and a smaller resistor 14. The larger resistor 13 is connected to the common positive line via a small resistor 15 and the smaller resistor 14 is connected to the earth terminal of the first 15 battery 1. Thus for constant V2, Vref tracks changes in V1 and changes in the output of the potential divider are a fraction of the causative changes in V1.

Referring to Figure 3, it can be seen that the reference voltage Vref exceeds the output of the potentiometer for V1 above about 13.2V with V2 = 12V.

20 When Vref exceeds the output of the potentiometer, the output of the operational amplifier 11 rises above the reference voltage Vref. The output of the operational amplifier 11 is supplied to the non-inverting input of the integrated comparator 12 via a second resistor 16. Consequently, when the output of the operational amplifier 11 rises above the reference voltage Vref, the output of the integrated 25 comparator 12 goes to its positive limit, turning on the solid-state switch 6.

The non-inverting input of the integrated comparator 12 is connected to the ignition switch 3 via a diode 19 and a large-value capacitor 17. The positive end of the capacitor 17 is connected to the negative terminal of the second battery 2 by a 30 large-value resistor 18. Thus, when the ignition switch 3a, 3b is turned from its first position to its second position, the capacitor 17 charges rapidly, applying a positive voltage to the non-inverting input of the integrated comparator 12. This voltage exceeds the reference voltage Vref, causing the output of the integrated comparator 12 to go positive thereby turning on the solid-state switch 6. The capacitor 17 can only discharge slowly through the large-value capacitor 18 which ensures that the solid-state switch 6 remains turned on for 40 seconds after the ignition switch 3a, 3b has been turned to its second position from its first position.

It can be seen from the foregoing that the timer 8 is implemented by the capacitor 17 and the large-value resistor 18 and that the OR-ing circuit 9 comprises the diode 19, the second resistor 16 and the integrated comparator 12.

lo Many modifications may be made to the exemplary embodiment described above, for instance to adapt the system to vehicles having 6, 24 or 42V electrical system.

Referring to Figure 4, the first battery 1 may be a lead-acid accumulator having a plurality of electrode plates 21. Each plate 21 comprises a frame 22 containing 15 porous lead (negative electrode) or lead oxide (positive electrode) 23. Each plate has a terminal 24 by which it can be connected to other plates in the same or different cells or to a battery terminal.

The frame 22 is in the form of a rectangular grid. However, it can be seen that the 2o apertures containing the lead or lead oxide 23 near the terminal 24 are smaller than those further away. Consequently, the current density in the frame remains more constant over the whole frame than is the case with a conventional regular frame. Preferably, the apertures are sized so that the current density in the frame material remains substantially constant over the whole frame 22.

Claims

1. A motor installation comprising a starter motor, 5 a first battery having an earth terminal coupled to the vehicle earth, a second battery, first switch means, second switch means for initiating operation of the starter motor, a controllable high-current switch means for selectively electrically coupling the earth terminals of the first and second batteries and control means, the non- earth terminals of the batteries being connected together, wherein the control means is configured to be responsive to operation of the first switch means to close the high-current switch means thereby coupling the earth terminals of the batteries.

2. A motor installation according to claim 1, wherein the second switch means cannot be operated until the first switch means has been operated to cause the highcurrent switch means to close.

2o

3. A motor installation according to claim 1, wherein the first and second switch means comprise respective poles of a multipole rotary switch.

4. A motor installation according to claim 1, 2 or 3, wherein the control means includes a timer circuit for causing the high-current switch means to reopen when a 25 predetermined period has elapsed since it was closed by operation of the first switch.

5. A motor installation according to any preceding, including voltage sensing means for sensing the voltage across the first battery, wherein the control means is 3o responsive to the voltage sensing means to close said high-current switch means when the voltage sensed by the voltage sensing means exceeds a predetermined voltage.

6. A motor installation according to any preceding claim, wherein the control means is powered from the second battery when the high-current switch means is open.

7. A motor vehicle including an installation according to any preceding claim.

8. A kit of parts for creating a motor installation according to claim 1, the kit comprising said second battery, said high-current switch means and said control means, the control means having an input and an output and being configured such lo that, when operational, the output changes to produce a signal for closing the highcurrent controlled switching means when a signal at the input undergoes a predetermined change.

9. A kit according to claim 8, wherein the control means includes a timer circuit 15 for causing the output to change to produce a signal for opening the high-current switch means when a predetermined period has elapsed since the input has undergone said predetermined change.

10. A kit according to claim 8 or 9, including voltage sensing means for sensing 20 the voltage across the first battery, wherein the control means is configured to be responsive to the voltage sensing means to output a signal for closing said highcurrent switch means when the voltage sensed by the voltage sensing means exceeds a predetermined voltage.

25

11. A motor starting system substantially as hereinbefore described with reference to Figure I of the accompanying drawings.

12. A motor starting system substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

Case: 34\732

13. Am electrode plate for a lead acid battery comprising an apertured frame and a terminal portion on the frame, wherein the cross-sectional areas of frame portions between apertures remote from the terminal portion are less than those near the terminal portion.

14. A battery including an electrode plate according to claim

13.

Amendments to the claims have been filed as follows LA motor installation comprising ò starter motor, a first battery having an earth terminal coupled to the installation's earth, ò second battery, first switch means, second switch means for initiating operation of the starter motor, a controllable high-current switch means for selectively electrically coupling lo the earth terminals of the first and second batteries and control means, the non earth terminals of the batteries being connected together, wherein the control means is configured to be responsive to operation of the first switch means to close the high-current switch means thereby coupling the earth terminals of the batteries.

2. A motor installation according to claim 1, wherein the second switch means cannot be operated until the first switch means has been operated to cause the high current switch means to close.

4. A motor installation according to claim 1, 2 or 3, wherein the control means includes a timer circuit for causing the high-current switch means to reopen when a predetermined period has elapsed since it was closed by operation of the first switch.

5. A motor installation according to any preceding, including voltage sensing means for sensing the voltage across the first battery, wherein the control means is responsive to the voltage sensing means to close said high-current switch means when the voltage sensed by the'voltage sensing means exceeds a predetermined voltage.

Case: 34\732 6. A motor installation according to any preceding claim, wherein the control means is powered from the second battery when the high-current switch means is open.

7. A motor vehicle including an installation according to any preceding claim.

8., A kit of parts for creating a motor installation according to claim 1, the kit comprising said second battery, said high-current switch means and said control means, the control means having an input and an output and being configured such lo that, when operational, the output changes to produce a signal for closing the highcurrent controlled switching means when a signal at the input undergoes a predetermined change.

25 11. A motor starting system substantially as hereinbefore described with reference to Figure I of the accompanying drawings.