JPS62268325A - Charging of electrochemical battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the charging of electrochemical secondary batteries. The present invention particularly relates to a method for charging a battery as described above, and particularly to a blank device for charging the battery.

According to one aspect of the invention, there is provided a method of charging at least one electrochemical secondary battery, comprising: supplying charging power to the battery and passing a charging current through the battery; when the potential of the battery increases to a predetermined voltage, the battery potential is further monitored, and when the battery potential rises to a predetermined voltage, establishing a low impedance electrical path parallel to the battery, and connecting this electrical path to the battery. A charging method is provided that includes shunting a charging current applied to the battery.

Charging may be interrupted when the potential of the battery rises to a predetermined or preselected value corresponding to a fully charged state of the battery.

Monitoring the battery potential may be performed by sensing the battery potential and comparing the sensed voltage to a reference voltage.

The potential of the battery may be sensed and compared to a reference voltage by a voltage comparator connected in parallel to the battery, which comparator connects the battery voltage to a precision voltage reference ( The output signal from the grain layer is
When the battery voltage rises to a predetermined voltage, LM l') 13
The connecting means can be configured to establish a low impedance path in parallel to the battery. The voltage divider preferably includes an adjustable variable resistor and two fixed resistors connected in parallel with the battery and in series with each other. Precision voltage base? (!The X value generator is preferably connected in series with a current limiting resistor. A precision voltage reference value generator and a current limiting resistor can also be connected in parallel to the battery.

Initially, a bypass, low impedance path is established, which causes the battery voltage to drop below a predetermined value. Therefore, the method according to the present invention makes it possible to periodically establish and dissipate a low impedance line, and in each cycle, the period during which the low impedance line is established is controllably changed depending on the potential of the battery. Ru. That is, the output signal from the comparator may be applied to switching means, which may be in the form of a transistor, with one of the switching means being
- A transistor is connected in parallel to the battery, which transistor is switched on when the output voltage from the comparator falls below a predetermined value. If the charging current applied to the battery 1-t-Ij flows through the bypass, the voltage of the battery will drop below the reference voltage. This is detected by the comparator and the result is an increase in the output voltage of the comparator (see above).
- Ranjisk is turned off. Thereby, if charging continues, the voltage of the battery increases again, and then the on/off state switching cycle of the transistor is performed again, and such operation is repeated intermittently.

In this way, a chop effect is obtained, and the battery charge is fllj
It is periodically interrupted by the establishment of a path. Typically,
The period during which the charging current supplied to the battery flows through the shunt established by the transistor is shorter than the interval between shunt establishments;
The battery is therefore effectively trickle charged. As the charging of the battery progresses, the interval between bypass establishments becomes progressively shorter, so that the proportion of time that charging current flows through the bypass increases.

If several batteries are connected in series with each other, the above-described shunt establishment can be performed simultaneously for any number of batteries in this battery string, with the shunt-established batteries having no relation to each other. It also has no substantial effect on cells that do not have a bypass established. None of the batteries is overloaded until all of the batteries connected in series with each other are substantially fully charged and the potential of the battery string rises to a predetermined value, in response to which charging is interrupted. It is not charging.

In this regard, when a battery bank consisting of several nominally discharged cells is charged by the potential applied to the battery bank, for example due to the fact that it occupies different positions in the battery with a temperature profile. As a result of differences in the internal resistance of the batteries due to differences in temperature between individual batteries, some batteries still require charging, and the potential of the battery string is = ﾥIt is pointed out that charging may be completed while the battery is still below a predetermined value corresponding to being charged to -). Under conditions like G) above, a charger that automatically interrupts charging when the potential of the battery string reaches the predetermined value above will continue charging, and charging current will flow to the battery that has finished charging too early. continue. A battery whose charge is completed prematurely may become overcharged and its internal resistance may rapidly increase, resulting in severe overage and risk of destruction.

Preferably, the output of the comparator, via a switching transistor connected in series with a resistor connected in parallel to the battery, activates a power transistor connected directly in parallel to the battery, thereby effectively A route is established. That is, the output of the switching transistor activates the power transistor and can also activate the indicating transistor.A light emitting diode connected in parallel to the battery and a resistor are connected in series to the indicating transistor. For safety reasons, a reverse biased protective tie-out may be connected in parallel to the battery.

Charging power may be supplied from any suitable power source, which may be a constant current power source or a power source that is easily current limited.
4 Ru.

The present invention also provides a protection device for use in charging at least one secondary battery, the device including at least one protection circuit connected in parallel to the battery and configured to monitor the voltage of the battery. and a monitoring means responsive to the monitoring means, which establishes a low impedance path when the monitored voltage rises to a predetermined value, and a side of the charging current directed to the battery. and switching means operable to provide a path.

The monitoring means includes a comparator that can be connected in parallel to the battery, a precision voltage reference (direct generator,
The battery may include a voltage divider circuit that includes three variable resistors connected in parallel to the battery. The output of the comparator σ) may be connected to switching means, the switching means being connected in parallel to the battery to establish a bypass of the charging current. The switching means, which may include a transistor, may be configured to automatically extinguish the shunt when the monitored battery voltage drops below a predetermined value in response to establishment of the shunt.

The switching means may preferably include a switching transistor connected in series with a resistor connected in parallel to the battery, the output of the comparator being connected to the switching transistor The output of is connected to a power transistor that establishes a bypass, connected directly in parallel to the battery. The output of the switching transistor may also be connected to an indicating transistor,
This indicator is connected in series with a light emitting diode connected in parallel with a battery and preferably with a resistor.

The protection circuit also includes a protection gate connected in parallel to the pond.

The protection device may be permanently connected to a plurality of cells connected in series with each other and may form part of a battery consisting of said cells, but may also be used in conjunction with a battery charger if the mass of the batteries is a concern. −・Part preferably constituted. In any of the above cases, the protection circuit can be a printed wiring board provided on a wiring board, and the printed wiring board is a unit that can be mounted on a subframe that forms part of a battery charger, for example. It has an edge connector to achieve this.

A protection circuit is preferably installed for each battery.

Each protection circuit has a pair of input terminals that can be connected to a charging power source and a pair of output terminals that can be connected to terminals of an associated battery. The heat cutting means may then be connected in parallel to the pair of output terminals.

The indicator 1 helangister is used to monitor charging = 12
- It is noted that the computer may be provided with a digital signal regarding the state of charge of the individual cells in the battery bank, which digital signal may be used to calculate the desired output current of the battery charger. be. The protection circuit may also provide an analog output from the battery terminals to, for example, a drag recorder.

The present invention further provides a battery charging system for charging a battery including a plurality of rechargeable electrical storage batteries connected in series with each other, the system comprising a plurality of rechargeable electrical storage batteries connected in series with each other. It includes a battery constituted by cells and a protection device as described above connected in parallel to each cell.

In this system, the protection device may form part of and be formed integrally with a charger for charging the battery, and the protection device may be connected in parallel to the battery.

The invention will be explained in more detail below by way of specific examples and with reference to the accompanying schematic drawings, in which: FIG.

In FIG. 1, a protection circuit which forms part of a protection device according to the invention is designated as a whole by the reference numeral 10.

In accordance with the method of the invention, a protection circuit 10 protects one cell of a battery bank from overcharging during charging of a battery bank of several electrochemical secondary batteries interconnected in series. used for. The circuit 10 includes an input terminal 11 that is connected to a battery charger (not shown) and an output terminal 1 that is connected to the positive and negative terminals of a battery (also not shown).
4 and 16.

The battery charger is connected directly to the battery by lines 18 and 20.

TL33], two input terminals of the CD comparator 22 (7, 4
) are connected to line 18 by lines 24 and 26, respectively.
and 20. Another input terminal (2) of the comparator 22 is connected by a line 28 with a variable resistor 30 to 56k and 471 (10 connected in series with a fixed resistor 32, 34) between lines 18 and 20; A further input terminal (3) of the comparator 22 is also connected by a line 36 between an LM385 Zener diode 38 and a 2 to 2 fixed current limiting resistor 40, which constitute a precision voltage reference value generator.

The output (6) of comparator 22 is connected to 2N30 by line 42.
53 is connected to the input of switching 1 to transistor 44, in which case line 42 is also connected to line J8 via a fixed bias resistor 46; lines 48 and 10
1 (connected to line 20 via fixed resistor 50).

The output on line 52/\ from the I/U register 44 is sent to the input of the MJ802 Power 1-Lance 54 which is connected directly between the I/U registers 18 and 20. 2N2222
The input of indicator transisk 56 is connected to line 52, and transistor 56 is connected in series between lines 18 and 20 with a light emitting diode 58 and a 220 ohm resistor 60.

A reverse biased protection diode 62 is connected between lines 18 and 20 to avoid damage caused by connecting the battery charger to input terminal 11 with the wrong polarity.

Circuit 10 has a voltage of 2.695 across battery terminals 14.16.
It is chosen to never exceed V. Comparator 22 is selected such that its operating voltage is 2V, and voltage reference generator 38 is set to 2.695V.

In use, when the battery is in a discharged state, the comparator 22 first detects that the voltage across the terminals 14.16 is equal to the set value 2.
Sensing the drop below 695V sends a voltage signal on line 42 that maintains transistor 44 and therefore transistor 54 off. As battery charging progresses, the voltage across battery terminals 14,16 approaches 2.7V, and before battery charging is complete, said voltage equals the set value of reference value generator 38; The output voltage signal sent from transistor 22 to line 42 decreases and transistors 1 to 44 are switched on. The output signal sent from the turned off transistor 44 to the line 52' switches the transistor 54 into the turned on state, thereby causing the transistor 54 to establish a low f-impedance path to charge the battery. Configures a current bypass.

As soon as the charging current to the battery flows through the bypass terminal 14.1
The voltage across line 42) decreases from comparator 22 to line 42)\
The sent No. 13 turns off the transistor 44 to LJJ.
The I.Landisk 44, which has increased to a value of
The side road disappears. The voltage across terminals 14,16 begins to increase gradually again and the switching cycle is thus repeated throughout the charging of the battery bank.

A chop effect acting on the charging current to the battery is induced, and as the degree of charge of the battery increases, the interval between successive establishments of a bypass becomes shorter and shorter, and eventually the establishment of a bypass becomes more or less occurs without any interruption, resulting in a trickle charge of the battery, until the charging of the battery bank is cut off by [1].

In the special case where the battery charger used is designed to automatically interrupt charging as soon as the voltage of the battery string (battery) rises to a predetermined value, the method and device of the invention can be used to has the particular advantage that all batteries can be substantially fully charged. Charging of other batteries, as mentioned above, [the charging current applied to a battery that has been fully charged before being diverted to the stream, i.e. Charging is effectively discontinued while the battery continues to be charged (although trickle charging continues) if the battery completes charging later. When all batteries are substantially fully charged (in which case the charging current to none of the batteries is momentarily diverted), the voltage in the battery string is set to a value that causes the charger to automatically interrupt charging. rise to

If the method of the present invention is used, for example, if a battery in a battery string has a temperature profile, it is possible for a battery to complete charging before another battery due to the internal resistance difference caused by the temperature difference. may become overcharged before the other batteries are fully charged.

If charging is not interrupted prematurely, i.e. before all the cells are fully charged, the battery components will be overcharged, resulting in potential problems such as poisoning of the solid electrolyte and decomposition of the liquid electrolyte. problems occur, and since no shunt is established, the entire charging current flows to a fully charged or overcharged battery, resulting in significant battery loss (L) due to overheating. Or destruction actually occurs.

According to the invention, the battery capacity is fully utilized as each battery can be fully charged without damage to any of the batteries due to overcharging, and damage due to overcharging is reduced, if not eliminated. This makes maintenance easier. If the battery mass is a concern, the 'IW protection device may form part of the charger.

In other cases, the protection device may form part of the battery, and the selection of the operating voltage of the comparator as well as the setting of the reference voltage
If a protection circuit is permanently connected to a battery, it can be done at values that make the circuit substantially 1 to 1.0 volts transparent to the battery (eg, 2 volts and 2 volts, respectively, in the circuit shown in FIG. 1). 695V).

The circuit illustrated in FIG.
Six accumulators with an open circuit voltage of 6 µm were tested using a nominally 2-equally interconnected battery bank. Each cell consists of a molten thorium anno-1'', a heta-alumina separator whose internal resistance is temperature sensitive, NaAlC1 separated from the helium by this separator, a liquid electrolyte, and an active material in contact with the liquid electrolyte. Fe/FeCl2 as cathode material.

The six batteries described above were charged and discharged for several cycles without using the method of the present invention. When we charged these batteries connected in series by applying a common charging current to the six batteries with a potential of about 12-15V applied to the battery string, we found that, as is common in such cases, Some of the cells exhibited different internal resistances which caused differences in the degree of charge of the cells.

The method of the invention was applied for the first time in the fifth charging cycle and continued for the sixth charging cycle.

At that time, one protection circuit shown in FIG. 1 was connected to each battery. FIG. 2 shows the voltages of the six batteries at the sixth charging cycle as well as the sixth discharging cycle of the six batteries.
It is a graph showing changes in the capacity (All) of the entire battery. As can be seen from this figure, the four batteries are fully charged before the remaining two (after about 25 Atl).
. However, a protection circuit keeps the voltage of the four previously charged batteries below 2.75V until the remaining two batteries are fully charged (as indicated by the battery voltage rise after about 40 AH). maintained at a safe value.

The method of the invention was further applied to the seventh and seventh charging cycles. FIG. 3 shows the charging cycle for the first battery along with the discharge cycle for the second battery. From FIG. 3 it can be seen that after several charging cycles according to the method of the invention, the six batteries exhibit charging characteristics that are substantially more similar to each other than in the ideal case where the charging characteristics of the individual cells are the same. The surprising advantage of being close to (=1) becomes clear.
Appears only in A Hflc (approximately 25 A I in Figure 2)
be compared to f). Furthermore, the battery capacity improved significantly from the sixth discharge cycle to the sixth discharge cycle. Since the battery is fully discharged and requires recharging when the discharge voltage drops to 9V (see Figure 4), approximately 33811 times are discharged during the sixth discharge cycle, and the battery is discharged until the second discharge cycle. In this case, approximately 40Δ11 was discharged.

FIG. 4 shows the fourth discharge cycle (before application of the method of the present invention);
3 is a graph similar to FIGS. 2 and 3 showing the change in overall battery voltage with respect to overall battery capacity during the first discharge cycle and the sixth and sixth charge cycles; FIG. This graph shows that for the battery as a whole, the method and device of the present invention reduces the charging voltage, substantially increases the capacity, and prevents individual batteries from being overcharged. It is clear that the inherent advantages of reduced battery damage and increased battery life are obtained.

Finally, although the invention has been described herein with respect to a plurality of batteries connected in series with each other, the invention applies equally to a plurality of batteries connected in series/parallel with each other;
That is, it is understood that it can also be used, for example, when a plurality of batteries are connected in parallel to each other between the terminals of a battery charger and these batteries are charged at once. Furthermore, it is understood that the protection circuit according to the invention can also be used to trickle charge a single battery to its full capacity.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a protection circuit forming part of a protection device according to the invention; FIG. A graph showing the change in battery voltage with respect to battery capacity.
A graph similar to FIG. 2 showing the voltage changes over a discharge cycle; FIG. 4 is a graph similar to FIG. This is a graph similar to . 2.3.4.7.1.1... Input terminal, 6...
...Output, 1o...Protection circuit, 14.16.
...Output terminal, 18, 20, 24, 26° 28.
36, 42, 48.52... line, 22-...
Yamabi grain layer, 3o...variable resistor, 32, 34.5
0...Fixed resistor, 38...Mountain Zener diode, 4
0... Current limiting resistor, 44... Switching resistor, 46... Bias resistor, 54...
...Power trunk, 56...For instructions
・Lansistor, 58・-Light emitting diode, 6o・・・・
...Resistor, 62...Protection guide. Representative Patent Attorney Itaru Nakamura

Claims (15)

[Claims] (1) A method for charging at least one electrochemical secondary storage battery, comprising: supplying charging power to the battery, passing a charging current through the battery, and when the potential of the battery rises to a predetermined value; suspending charging, further monitoring the potential of the battery, and establishing a low impedance path in parallel to the battery when the potential of the battery rises to a predetermined voltage; A charging method including shunting current. (2) The method according to claim 1, wherein the monitoring of the battery potential is performed by sensing the battery voltage and comparing the detected voltage with a reference voltage. 3. The method of claim 2, wherein the comparison is performed by a voltage comparator configured to compare the battery voltage with a precision voltage reference value. (4) The method of claim 3, wherein the output signal from the comparator is configured to activate the switching means, thereby establishing a low impedance path in parallel to the battery. . (5) A patent claim characterized in that the establishment and disappearance of the low-impedance circuit are performed periodically, and the period during which the low-impedance circuit is established in each cycle is controllably changed depending on the potential of the battery. The method described in item 1 of the scope. (6) A patent claim characterized in that a plurality of batteries connected in series are charged simultaneously, and a low impedance circuit is selectively established for each individual battery depending on the state of charge of the battery. The method described in Scope No. 1. (7) A protection device used for charging at least one secondary storage battery, including at least one protection circuit that can be connected in parallel to the battery, the protection circuit operating to monitor the voltage of the battery. monitoring means responsive to the monitoring means and operable to establish a low impedance path to bypass charging current applied to the battery when the monitored voltage rises to a predetermined value; and a protective device comprising switching means. (8) a comparator, the monitoring means of which may be connected in parallel to the battery, a precision voltage reference value generator supplying a reference voltage to the comparator, and an input signal which may be connected in parallel to the battery and is proportional to the voltage of the battery; 8. A device according to claim 7, characterized in that it includes a voltage divider circuit that provides a comparator with . 9. The device of claim 8, wherein the voltage divider includes a variable resistor that produces an adjustable variable input signal proportional to the voltage of the battery. (10) The switching means is controlled to periodically realize the establishment and disappearance of the low impedance circuit, the period of said establishment and disappearance being dependent on the relationship with a predetermined value of the monitored battery voltage for each period. 8. Device according to claim 7, characterized in that the device varies from one to the other. (11) A patent characterized in that the switching means includes a switching transistor responsive to a comparator and a power transistor responsive to the switching transistor and forming a part of a low impedance circuit. A device according to claim 7. 12. The device of claim 7, further comprising indicating means operable to indicate that the battery is being charged. (13) A patent claim further comprising a reverse-biased protection diode operable to minimize damage caused by connecting the protection device with the battery in the wrong polarity. The device according to scope 7. (14) A battery charging system for charging a battery comprising a plurality of rechargeable electrochemical storage batteries connected in series with each other, the battery comprising a plurality of said batteries connected in series with each other; , and a protection device according to claim 7 connected in parallel to each battery. (15) The protection device is integrally formed with the battery charger, further comprising a battery charger operable to supply charging current to the battery. system.