JP3959243B2 - Method for preventing internal pressure rise of battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for charging an assembled battery used as a power source of an electric motor in a hybrid vehicle using an electric motor (motor) and an internal combustion engine (engine) as drive sources.
[0002]
[Prior art]
In a hybrid vehicle using both an electric motor (motor) and an internal combustion engine (engine) as drive sources, an assembled battery in which a plurality of single batteries are combined is used as a power source for the electric motor. Since such an assembled battery needs to be mounted in a limited space in an automobile, it needs to be compact and lightweight. For this reason, a rectangular flat battery having a thin flat plate shape has been developed. This rectangular single battery is configured by accommodating an electrolyte and an electrode plate group in a plastic thin hollow rectangular battery case. Moreover, this single battery is provided with a safety valve for pressure adjustment.
[0003]
When the battery internal pressure of the single battery starts to rise, the safety valve operates to relieve the pressure in the battery case. However, if the internal pressure of the battery further increases, the battery case is made of plastic and may be damaged.
[0004]
When the internal pressure of the battery rises, it is at the time of overdischarge, overcharge, when the gas absorption performance is lowered at low temperature, or the like.
[0005]
In a hybrid vehicle, the temperature, voltage, current, etc. of the single battery constituting the assembled battery are measured, the remaining battery capacity (SOC) is estimated, and the power that can be input to and output from the assembled battery is calculated. Control is performed within a range of possible power. In such control, for example, the input / output of the assembled battery is limited in accordance with the level of the battery temperature, the level of the remaining battery capacity, and the like. By using the battery within the rechargeable range of the battery, there is no possibility of suddenly being unable to extract power due to a decrease in the remaining battery capacity (SOC) or the like. Therefore, it is possible to secure power performance such as elimination of discomfort during traveling of the hybrid vehicle and extension of the travelable distance.
[0006]
[Problems to be solved by the invention]
When a battery pack in which a single battery is combined is used as a power source for a hybrid vehicle, a current is used and discharged during traveling, and the amount of stored electricity is reduced. At this time, variation occurs in the storage amount of each single battery. Each single battery in which the amount of stored electricity is reduced is uniformly charged by being charged uniformly by a constant current. The equal charge is charged with a constant current so that all the batteries are overcharged.
[0007]
As described above, when the battery packs are uniformly charged, each single battery is overcharged, and thus the internal pressure of the overcharged single battery increases linearly from reaching full charge. When the battery pack is uniformly charged, the pressure reaches the pressure at which the safety valve for preventing the internal pressure rises, and if the battery is further charged, the pressure may reach the pressure limit of the battery case. In particular, in a plastic prismatic battery, there is a high possibility that the battery case will reach the pressure limit due to the increase in internal pressure.
[0008]
Moreover, the input / output power of the conventional assembled battery is determined by estimating the remaining battery capacity (SOC), but no consideration is given to the increase in the internal pressure of the battery. Therefore, it is impossible to determine whether or not the battery internal pressure is increased only by the remaining battery capacity (SOC), and as a result, the battery case may reach the pressure limit due to the increase of the internal pressure. There is also.
[0009]
The present invention solves such a problem, and an object of the present invention is to provide a method for charging an assembled battery that is effective in suppressing expansion of the battery case or reaching a withstand voltage limit during equal charging of the assembled battery. There is. Another object of the present invention is to provide a method for preventing an increase in the internal pressure of an assembled battery, which can prevent the battery case from reaching the withstand voltage limit.
[0010]
[Means for Solving the Problems]
The present invention is a method of charging an assembled battery including a plurality of single batteries, wherein the first current is applied by a first current until the internal pressure of at least one single battery of the plurality of single batteries starts to increase. A first step of charging each single battery at a rate and a second current lower than the first rate by a second current lower than the first current after the internal pressure of the at least one single battery starts to rise. And a second step of charging / discharging each single battery at a rate of 2, thereby achieving the object.
[0011]
Another aspect of the present invention includes the plurality of unit batteries, wherein the second step includes a step of charging each unit battery and a step of stopping charging / discharging of each unit battery. This is a method of charging an assembled battery.
[0012]
Another aspect of the present invention is an assembled battery including the plurality of unit batteries, wherein the second step includes a step of charging each unit battery and a step of discharging each unit battery. It is a method of charging.
[0013]
In another aspect of the present invention, the second step includes a step of charging each single battery, a step of discharging each single battery, and a step of stopping charging / discharging of each single battery. And charging a battery pack including the plurality of single batteries.
[0014]
In another aspect of the present invention, the first rate is 1.6 to 3.0C, and the second rate is 0.3 to 1.5C. A method for charging a battery.
[0015]
Furthermore, the present invention is based on the step of detecting the temperature of the single battery, the step of estimating the internal pressure of the single battery, the detected temperature of the single battery, and the estimated internal pressure of the single battery. A step of determining whether or not the battery case that is a single battery container constituting the assembled battery may reach a pressure limit; and if it is determined that the battery case may reach a pressure limit, The method for preventing an increase in the internal pressure of the assembled battery, including the step of restricting input / output to the assembled battery by performing the second step described in the above, achieves the above object.
[0016]
According to another aspect of the present invention, the determination as to whether or not the battery case may reach a pressure limit is performed using a map indicating a pressure limit determined in advance for the battery case. This is a method for preventing an increase in internal pressure of an assembled battery.
[0017]
In another aspect of the present invention, the estimation of the internal pressure of the single battery is based on a remaining battery capacity (SOC) of the single battery, the temperature of the single battery, and a charge / discharge current of the single battery. The method for preventing an increase in internal pressure of the assembled battery as described above.
[0018]
In another aspect of the present invention, the remaining battery capacity (SOC) of the single battery is determined based on the voltage of the single battery, the charge / discharge current of the single battery, and the temperature of the single battery. The method for preventing an increase in internal pressure of the assembled battery as described above.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The term “rate” used in this specification means “charge rate” or “discharge rate”. In addition, the term “single battery” used in this specification refers to “single battery” or “a plurality of single batteries inserted into one battery case, and a pair of plus and minus terminals outside the case. It means “unit battery”. The method for preventing an increase in internal pressure of an assembled battery according to the present invention is performed, for example, when an assembled battery made of a sealed nickel-hydrogen storage battery used as a power source for an electric motor in a hybrid vehicle is charged equally. This equal charging method will be described based on the graph of FIG. When the assembled battery is charged uniformly, as shown by a solid line in FIG. 1A, first, the battery is charged with a constant current at a rate of 2C until the remaining battery capacity (SOC) reaches 100%. Usually, the charging at the constant current of 2C is about 30 minutes. When the SOC reaches 100%, the battery is charged for about 40 minutes with a relatively low rate current of about 0.3 to 1.5 C lower than the charging current.
[0020]
In this case, as indicated by a solid line in FIG. 1B, the internal pressure of the single battery is substantially constant until the SOC reaches 100%, and when the SOC exceeds 100%, the internal pressure increases. However, in this case, since the charging current is not a 2C but a low rate of about 0.3 to 1.5C, the internal pressure of the single battery only rises gently. For comparison, an increase in internal pressure when the battery is uniformly charged with only a constant current of 2C is shown by a broken line in FIG.
[0021]
Further, as shown by a solid line in FIG. 2A, in order to reliably prevent an increase in the internal pressure of the single battery after charging with a current of 2C and SOC exceeding 100%, 0.3-1 The charging may be stopped after the low rate charging of about 5 C is performed for a predetermined time. As a result, as indicated by a solid line in FIG. 2B, there is no possibility that the internal pressure of the single battery will increase after the charging is stopped.
[0022]
Further, as shown by a solid line in FIG. 3A, the battery is charged with a current of 2C, and the internal pressure of the single battery after the SOC exceeds 100% is reduced, about 0.3 to 1.5C. Each of the single batteries may be discharged after the low-rate charging is performed for a predetermined time. As a result, as shown by a solid line in FIG. 3B, after discharging, the internal pressure of the single battery decreases.
[0023]
Furthermore, as shown in FIG. 4 (a), when the battery is charged with a constant current of 2C until the battery remaining capacity (SOC) reaches 100%, thereafter, a low rate charge of about 0.3 to 1.5C, Charging suspension and charging may be repeated alternately. The low rate charging and the charging suspension are set to appropriate times of about 10 seconds to 40 minutes, respectively. In this case, as shown in FIG. 4 (b), after the SOC exceeds 100%, the internal pressure of the single battery only rises gently due to the low rate charging of about 0.3 to 1.5C. In addition, the internal pressure of the single battery decreases due to the suspension of charging. Therefore, the increase in the internal pressure of the single battery is reliably suppressed by repeating the charging at a low rate of about 0.3 to 1.5 C and the charging suspension.
[0024]
Furthermore, as shown in FIG. 5 (a), when the battery remaining capacity (SOC) reaches 100%, the battery is charged with a constant current of 2C, and thereafter, a low rate charge of about 0.3 to 1.5C is performed. The discharge and the discharge may be alternately repeated. The low-rate charging and discharging time is set to an appropriate time of about 10 seconds to 40 minutes, but the discharging is set shorter than the charging time. In this case, as shown in FIG. 5 (b), after the SOC exceeds 100%, the internal pressure of the single battery only rises slowly by charging at a low rate of about 0.3 to 1.5C. In addition, due to the discharge of each single battery, the internal pressure of the single battery is surely lowered. Therefore, the increase in the internal pressure of the single battery is more reliably suppressed by repeating the charging and discharging at a low rate of about 0.3 to 1.5 C.
[0025]
Still further, as shown in FIG. 6A, if the battery is charged with a low current of 2C until the remaining battery capacity (SOC) reaches 100%, then a low rate charge of about 0.3 to 1.5C is performed thereafter. And charging suspension and discharging may be repeated in order. Low rate charging, charging suspension and discharging time are set to appropriate times of about 10 seconds to 40 minutes. In this case, as shown in FIG. 6 (b), after the SOC exceeds 100%, the internal pressure of the single battery only rises slowly by charging at a low rate of about 0.3 to 1.5C. is there. Moreover, the internal pressure of a single battery will fall by charging suspension, and also the internal pressure of a single battery will fall reliably by discharge of each single battery. Therefore, the increase in the internal pressure of the single battery is more reliably suppressed by repeating the charging at a low rate of about 0.3 to 1.5 C, the charging suspension, and the discharging.
[0026]
In addition, you may change the order of the low rate charge of about 0.3-1.5C, charge rest, and discharge at random.
[0027]
In the equal charging method in each of the above embodiments, charging is performed at a rate of 2C until the remaining battery capacity reaches 100%. However, charging can be performed at other rates. However, when the rate is much higher than 2C, the charging efficiency decreases and the battery internal pressure increases. In addition, when the rate is much lower than 1.6C, the charging time becomes long, which is not preferable as an assembled battery for a power source of an electric motor such as a hybrid vehicle. Therefore, a rate of about 2C is preferable. In addition, the lower the rate after the battery remaining capacity reaches 100%, the lower the increase in internal pressure of the battery, but the longer the charging time is. Therefore, a rate of about 0.3 to 1.6C is preferable.
[0028]
In this way, when charging the assembled battery evenly, it is possible to prevent an increase in the internal pressure of each single battery, so in the single battery having a square battery case made of plastic, the release of gas due to the opening of the safety valve is eliminated, The battery life can be improved. Furthermore, there is no fear that the battery case reaches the pressure limit. Moreover, in the assembled battery that combines the single batteries having a square battery case, since the expansion of the battery case is suppressed by suppressing the increase in the internal pressure of each single battery, the dimensions for restraining each single battery It is economical because it is not necessary to use high-precision parts.
[0029]
FIG. 7 is a schematic configuration diagram of an internal pressure rise prevention device used in the implementation of the method for preventing an internal pressure rise of the assembled battery of the present invention. For example, in the assembled battery 10 in which a plurality of single batteries 11 each having a plastic battery case are combined, the internal pressure rise prevention device is configured to increase the internal pressure of at least one single battery among the single batteries 11. The voltage measuring means 12 for measuring the voltage of any single battery 11 in the assembled battery 10, the current measuring means 13 for measuring the charge / discharge current value of the single battery 11, and the single battery 11 and a temperature measuring means 14 for measuring the temperature of the battery case.
[0030]
The outputs of the voltage measuring means 12, the current measuring means 13 and the temperature measuring means 14 are respectively given to the battery remaining capacity calculating section 15, and the output of the battery remaining capacity calculating section 15 is given to the battery internal pressure increase determining section 16. It has been. The battery internal pressure increase determination unit 16 is also provided with the output of the current measuring means 13 and the output of the temperature measuring means 14. The battery internal pressure increase determination unit 16 determines whether the internal pressure of the battery is increasing based on the battery internal pressure increase determination map 17 and outputs a predetermined signal to the battery input / output limiting unit 18. The battery input / output restriction unit 18 restricts input / output to the assembled battery 10 based on the output of the battery internal pressure increase determination unit 16.
[0031]
In the battery internal pressure increase determination map 17, battery internal pressure characteristic data obtained in advance for each battery type and plastic battery case withstand voltage data are obtained in advance and stored as a map. In general, the battery internal pressure characteristics are determined by the battery remaining capacity (SOC), the battery temperature, and the charge / discharge current value, and are roughly shown in FIG. It can be seen from the battery internal pressure characteristics shown in FIG. 8 that the battery internal pressure is relatively low when the remaining capacity of the battery is about 20 to 80%. Further, it can be seen that when the temperature and the current value rise, the battery internal pressure value rises throughout.
[0032]
Moreover, the pressure resistance characteristics of the battery case in the single battery 11 having a plastic battery case are determined by the battery internal pressure and the battery (battery) temperature, and are roughly shown in FIG. From the characteristics shown in FIG. 9, in the range of about 20 to 60 ° C., the possibility of reaching the pressure limit is low even if the internal pressure increases, but when the temperature exceeds 60 ° C., the pressure limit of the battery case increases as the temperature increases. It can be seen that the internal pressure value shown gradually decreases, and when the internal pressure value falls below 20 ° C., the internal pressure value indicating the pressure limit of the battery case decreases.
[0033]
A graph showing the battery internal pressure characteristics shown in FIG. 8 and a graph showing the battery case pressure resistance characteristics shown in FIG. 9 are held in the battery internal pressure increase determination unit 16 as a battery internal pressure increase determination map 17.
[0034]
FIG. 10 is a flowchart showing the control contents of the internal pressure rise prevention device having such a configuration. For example, when the battery pack 10 is charged uniformly as described above, the internal pressure rise prevention device uses the voltage measurement means 12, the current measurement means 13, and the voltage, current, and temperature of a predetermined single battery 11 in the battery pack 10. The temperature is measured by the temperature measuring means 14 (see step S1 in FIG. 10, the same applies hereinafter). Then, the measured voltage, current, and temperature of the single battery 11 are input to the battery remaining capacity calculation unit 15, and the remaining capacity of the single battery 11 is calculated by the battery remaining capacity calculation unit 15.
[0035]
The battery remaining capacity of the single battery 11 calculated by the battery remaining capacity calculation unit 15 is given to the battery internal pressure increase determination unit 16. The battery internal pressure increase determination unit 16 is also provided with the current of the single battery 11 obtained by the current measurement unit 13 and the temperature of the single battery 11 obtained by the temperature measurement unit 14, respectively. The battery internal pressure is estimated based on these calculated values and measured values and the battery internal pressure increase determination map 17 (step S3).
[0036]
Specifically, based on the remaining battery capacity of the single battery 11 and the temperature and current value of the single battery 11, the internal pressure of the single battery 11 is estimated from the battery internal pressure characteristic graph shown in FIG. Based on the measured battery internal pressure and the temperature of the single battery 11, it is determined whether the measured single battery 11 is located within the pressure limit of the battery case from the graph showing the pressure resistance characteristic of the battery case shown in FIG. (Step S4).
[0037]
And when the internal pressure of the single battery 11 is less than the pressure | voltage limit of a battery case, normal input / output is implemented with respect to the assembled battery 10 (step S5). On the other hand, when the internal pressure of the single battery 11 is in the vicinity of the pressure limit of the battery case, it is determined that the internal pressure of the single battery 11 is high and the battery case may reach the pressure limit. Input / output with respect to is restricted (step S6). As a result, an increase in internal pressure of all the single batteries 11 in the assembled battery 10 is prevented, and the battery case of each single battery 11 is prevented from reaching the pressure limit.
[0038]
【The invention's effect】
As described above, the method for charging an assembled battery according to the present invention can suppress an increase in the internal pressure of a single battery when charging the assembled battery evenly, and accordingly, the battery case reaches a withstand voltage limit. Can be prevented. Furthermore, since the present invention does not require an expensive and precise internal pressure sensor or the like as in the prior art, the cost can be reduced and the reliability is also improved.
[Brief description of the drawings]
FIG. 1A is a graph showing an example of an implementation state of an assembled battery equalizing method in which the assembled battery charging method of the present invention is implemented, and FIG. 1B is a graph showing the internal pressure of the battery in that case. It is.
FIG. 2 (a) is a graph showing another example of the state of charge equalization of the battery pack in which the battery pack charging method of the present invention is implemented, and FIG. 2 (b) shows the internal pressure of the battery in that case. It is a graph.
FIG. 3A is a graph showing another example of the state of equal charge of an assembled battery in which the method of charging an assembled battery of the present invention is implemented, and FIG. 3B shows the internal pressure of the battery in that case. It is a graph.
FIG. 4A is a graph showing another example of the state of charge equalization of an assembled battery in which the method for charging an assembled battery of the present invention is implemented, and FIG. 4B shows the internal pressure of the battery in that case. It is a graph.
FIG. 5A is a graph showing another example of the state of charge equalization of an assembled battery in which the method for charging an assembled battery of the present invention is implemented, and FIG. 5B shows the internal pressure of the battery in that case. It is a graph.
6A is a graph showing another example of the state of charge equalization of an assembled battery in which the method for charging an assembled battery of the present invention is implemented, and FIG. 6B shows the internal pressure of the battery in that case. It is a graph.
FIG. 7 is a block diagram showing a configuration of a device used for carrying out in still another example of a method for charging a battery pack according to the present invention.
8 is a graph showing an example of battery internal pressure characteristics stored in a battery internal pressure increase determination map used in the apparatus shown in FIG. 7;
9 is a graph showing an example of a pressure resistance characteristic of a battery case stored in a battery internal pressure increase determination map used in the apparatus shown in FIG.
10 is a flowchart showing control contents of the apparatus shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Assembly battery 11 Single battery 12 Voltage measurement means 13 Current measurement means 14 Temperature measurement means 15 Battery remaining capacity calculation part 16 Battery internal pressure rise determination part 17 Battery internal pressure rise judgment map 18 Battery input / output restriction part

Claims (4)

A method for preventing an increase in internal pressure of an assembled battery including a plurality of single batteries,
Detecting the temperature of at least one single battery of the plurality of single batteries ;
Estimating the internal pressure of the single battery;
Determining a temperature of the single battery the detected, based on the internal pressure of the single battery the estimated, whether the container is a battery case of a single battery constituting the battery pack is likely to reach the withstand voltage limit And steps to
If it is not determined that the battery case is likely to reach the withstand voltage limit, the first current causes a first rate until the internal pressure of at least one of the plurality of single batteries starts to increase. Charging each single battery;
When the battery jar is determined that there is a possibility to reach the withstand voltage limit, after said internal pressure of the single battery has started to rise, lower than said first rate by said lower first current second current Limiting input and output to the assembled battery by charging and discharging each single battery at a second rate ;
A method for preventing an increase in internal pressure of the assembled battery. The internal battery pressure rise prevention of the assembled battery according to claim 1 , wherein the determination as to whether or not the battery case may reach a withstand voltage limit is performed using a map indicating a withstand voltage limit obtained in advance for the battery case. Method. Wherein said estimation of said pressure of the single battery, the remaining battery capacity of the single battery (SOC), and the temperature of the single battery is carried out based on the charge and discharge current of the single battery, according to claim 1 Method for preventing an increase in internal pressure of an assembled battery. Wherein the remaining battery capacity of a single battery (SOC) is a voltage of the single battery, and the charge and discharge current of the single battery is determined based on said temperature of the single battery, the set according to claim 3 Battery internal pressure rise prevention method.

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