JP4032436B2 - Internal temperature calculation device for secondary battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal temperature calculation device that calculates an internal temperature associated with operation of a secondary battery, that is, a battery that can be used by repeatedly charging and discharging.
[Prior art]
As a conventional secondary battery temperature detection device, it is usually considered to attach a sensor to the surface of the battery where the temperature is highest. It is also conceivable to install a sensor inside the secondary battery.
[Problems to be solved by the invention]
However, in such a conventional temperature detecting device for a secondary battery, the ambient temperature of the surface of the secondary battery (hereinafter simply abbreviated as a battery unless otherwise confused) is measured, and the inside of the battery is measured. When the sensor is attached to the battery, there is a problem that the internal temperature of the battery and the outside of the battery cannot be ensured in addition to the fact that the internal temperature of the battery cannot be accurately predicted for the reason described above.
[0002]
Therefore, a method of controlling the fan based on the value of TB + ΔT is considered, assuming that the difference between the surface temperature TB and the internal temperature TB0 is a predetermined value ΔT (a constant value). However, in such a method, when ΔT is different from the actual temperature difference, the cooling by the fan is stopped or the temperature inside the battery becomes low even though the inside of the battery is not sufficiently cooled. However, as a result of starting the cooling by the fan, there is a possibility that the battery is deteriorated or the battery performance cannot be sufficiently exhibited. An object of the present invention is to provide an internal temperature calculation device for a secondary battery that performs charge or discharge control of the secondary battery by paying attention to the problems of the prior art.
[0003]
[Means for Solving the Problems]
The above-described problem is achieved by calculating the battery internal temperature from the battery surface temperature and the fan output, and performing fan air blowing control and battery charge / discharge control using the calculated values. The cooling effect on the secondary battery installed and operating inside the wind tunnel fan case varies depending on the amount of air blown by the fan (fan output) and the temperature of the blown air. That is, the same battery 1 as described later Fig. 1, carried out an experiment based on experimental apparatus using the casing 8 and the fan 6, as shown in FIGS. 13 to 15, the cooling air flow amount Q from the output P of the fan 6 determined, then determine the heat transfer coefficient h from the cooling air flow quantity Q, further obtains the inside and outside temperature difference ratio α by the fan 6 from the heat transfer coefficient h. Thus, the internal / external temperature difference ratio α1 when the output P of the fan 6 is 0 and the internal / external temperature difference ratio α2 when the output P is the maximum value are calculated, and the internal temperature is calculated from the surface temperature of the battery 1. . In short, the present invention measures the surface temperature of the battery 1 installed in the case 8 according to the above-described procedure, calculates the internal temperature of the battery 1 from the surface temperature, and thereby controls the air flow of the fan 6 appropriately. The discharging or charging control of the battery 1 is executed.
[0004]
That is, according to the present invention, as described in the claims, the means for measuring the battery surface temperature of the secondary battery, the means for measuring the amount of air blown to the battery, and the air blown by the fan A means for measuring the temperature; a means for measuring the surface temperature of the battery; a means for measuring the amount of blown air; and a means for calculating the internal temperature of the battery from measurement values obtained by the means for measuring the blown air temperature. It is the internal temperature calculating apparatus of the secondary battery characterized.
[0005]
【The invention's effect】
The present invention calculates the internal temperature of the battery from the temperature of the battery surface and the fan output, and uses the value to control the fan air blowing, the battery charging and discharging, the fan efficiency is improved, The effect of increasing the charge amount or discharge amount of the secondary battery is obtained.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a detailed description will be given based on the embodiment of the present invention.
[0007]
<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS. First, the configuration of the present embodiment will be described. In FIG. 1, reference numeral 1 denotes a battery, which is connected to a charger 3 and a discharger 4 via a junction box 2. Switching is performed in the junction box 2 so that the battery 1 and the charger 3 are connected during charging, and the battery 1 and the discharger 4 are connected during discharging. Battery 1 around is covered in case 8, it is possible to manage the temperature of the battery 1 by the fan 6 for air blowing. The surface temperature of the battery 1 itself and the temperature of the atmosphere around the battery 1 are constantly measured by the battery temperature sensor 7a and the air temperature sensor 7b. The measurement signals of the battery temperature sensor 7a and the air temperature sensor 7b are input to the controller 5, and signals can be sent to the charger 3, the discharger 4 and the fan 6 by the calculation of the controller 5 for control.
[0008]
Next, the operation will be described. FIG. 2 is a diagram showing the control action of the fan. In this embodiment, when the battery is cooled, it is turned on when the battery temperature rises above a certain set value T F2 , and falls below a certain set value T F1 . It shows the control action to turn off. FIG. 3 is a diagram showing a control flow when the fan of FIG. 2 is controlled under the configuration of FIG. In FIG. 3, charging or discharging is started in step S11, and the surface temperature TB and air temperature T∞ of the battery 1 are measured in step S12. In step S13, the operation of the battery 1 is continued until the initial value TBO temporarily set based on the surface temperature TB obtained in step S12 exceeds the use limit temperature Tmax (approximately 70 ° C.) or it is determined that charging or discharging is finished. And the flow after step S14 is repeated.
[0009]
In step S14, it is determined whether or not the fan 6 is operating. First, the case where the fan 6 is not operating will be described. In step S15, the estimated battery internal temperature TBO is calculated using the internal / external temperature difference ratio α1 when the fan is OFF.
[0010]
The battery internal temperature TBO calculated in step S151 is compared with a set value TF1 (approximately 40 ° C.), and if TBO <TF1, the process returns to step S12 to continue charging or discharging. If TBO> TF1, the fan is turned on, waits for ON for a predetermined time t, and then returns to step S12. Next, the case where the fan 8 is operating will be described.
[0011]
In step S16, the estimated battery internal temperature TBO is calculated using the internal / external temperature difference ratio α2 when the fan is ON. The battery internal temperature TBO calculated in step S161 is compared with the set value TF2 (approximately 60 ° C.). If TBO> TF2, the process returns to step S12 to continue charging or discharging. If TBO <TF2, the fan is turned off, and after waiting for OFF for a predetermined time t, the process returns to step S12.
[0012]
FIG. 4 is a diagram showing the temperature distribution of each part inside and outside the battery in the first embodiment, and FIG. 5 is a diagram showing the relationship between the fan output and the internal / external temperature difference ratio α in the first embodiment. The internal and external temperature difference ratios α1 and α2 will be described with reference to FIGS. The battery 1 is deprived of heat from the surface by the air blown from the fan 6, and the temperature of each part inside and outside the battery 1 changes according to a temperature distribution curve as shown in FIG. If the ratio of the temperature difference between inside and outside is α,
α = (TB−T∞) / (TBO−T∞)
As shown in FIG. 5, α varies between 0 and 1 depending on the thermal conductivity from the battery surface to the cooling air, that is, the fan output. Therefore, α1 when the fan output is OFF and α2 when the fan output is ON, and α1 and α2 are obtained based on the experiment using the same battery 1, case 8, and fan 6 as in FIG. That is, FIG. 13 is a diagram in which the relationship between the fan output P and the cooling air flow rate Q is obtained. FIG. 14 is a diagram in which the relationship between the flow rate Q and the heat transfer coefficient h obtained by the same experiment is obtained. Next, by solving the heat conduction equation inside the battery 1, the relationship between the heat conduction coefficient h and the internal / external temperature difference ratios α1 and α2 is obtained from FIG.
[0013]
FIG. 6 and FIG. 7 are diagrams showing delay times due to fan OFF to ON or ON to OFF in the first embodiment. That is, in FIG. 6, the internal / external temperature difference ratio gradually decreases from α1 to α2 as time passes, and in FIG. 7, the internal / external temperature difference ratio gradually increases from α2 to α1 as time passes. As a result, as shown in steps S153 and S163, the temperature of the battery 1 is not stable for a predetermined time after the fan is turned on and off. Therefore, the internal temperature TBO of the battery 1 calculated during that time is equal to the actual internal temperature. Makes a difference. Therefore, during the t time ON or the t time OFF, the flow is not stopped without correcting the value of α1 or α2. The value of t time ON or t time OFF depends on the thermophysical property value and shape of the battery 1, but in the case of a lithium ion battery having a thickness of 24 mm, the temperature rise of the battery 1 is 1 ° C./min at the maximum. Therefore, the battery 1 is hardly affected by the above.
[0014]
The internal temperature of the battery 1 can be obtained more accurately from the battery surface temperature measured as described above and the output of the fan 6. As shown in FIG. 8, in consideration of safety in order to predict the battery internal temperature TBO from the surface temperature TB of the battery 1, ΔT must be expected to have a maximum value as TBO = TB + ΔTmax. Since ΔTmax is proportional to the temperature difference TB−T∞ between the output P of the fan 6, the battery surface temperature, and the air temperature, the output of the fan 6 is Pmax, and the temperature difference is the lowest air that must consider the heat resistance of the battery 1. In the case of the temperature T∞, it becomes a point marked with x in FIG. That is, the fan 6 is driven even though the internal temperature of the battery 1 is overestimated and does not reach the heat resistance limit. However, according to the present embodiment, although it varies depending on the output of the fan 6 and the temperature difference, it becomes an appropriate value equal to or less than ΔTmax, and the charging or discharging time can be continued longer. The output P of the fan 6 at this time can be substituted by the air flow rate Q.
[0015]
<Embodiment 2>
A second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the fan 6 is controlled as shown in FIG. In step S21, α corresponding to the output of the fan 6 is obtained from the relationship between the fan output P and the internal / external temperature difference ratio α shown in FIG. 5, and the internal temperature TBO of the battery 1 is calculated in step S22. In step S23, the output of the fan 6 is changed to the internal temperature TBO, and the process returns to step S12. The internal temperature TBO obtained in step S22 is used as the temperature value for determining whether to stop charging / discharging in step S13.
[0016]
In the present embodiment, there is no step change in the fan output as in the first embodiment, so that it is not necessary to provide a delay time such as steps S153 and S163 in the flowchart.
[0017]
<Embodiment 3>
The third embodiment will be described with reference to FIGS. In FIG. 11, a line L1 is a temperature rise line for guaranteeing the heat resistance of the battery. When it is in the area A1 above the line L1, the battery needs to be cooled, and when it is in the area A2 below the line L1. Since it is predicted that the battery does not reach the heat resistant temperature Tmax, it is considered that cooling is not necessary. In the present embodiment, it is determined in step S31 from the internal temperature TBO of the battery and the capacity of the battery whether the battery state is in the area A1 or A2 in FIG. Control to turn off the fan 6 is performed. The reason why such control is performed is that the temperature rises depending on the remaining capacity of the battery 1, and therefore, if it is predicted that the heat resistant temperature will not be reached, the fan 6 is stopped to save energy. It is.
[0018]
As described above, according to the present invention, the battery internal temperature is calculated from the battery surface temperature and the battery internal / external temperature difference ratio based on the fan output, and the fan control, charging or Since it is configured to perform discharge control, the battery can be operated without causing a problem such as stopping the driving of the fan despite the fact that the cooling effect of the battery by the fan does not appear as in the conventional case. The effect of increasing the discharge amount is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of Embodiment 1 of an internal temperature calculation device for a secondary battery of the present invention.
FIG. 2 is a diagram illustrating fan control according to the first embodiment.
FIG. 3 is a flowchart according to the first embodiment.
4 is a diagram showing a temperature distribution inside and outside the battery according to Embodiment 1. FIG.
5 is a diagram showing a relationship between fan output and internal / external temperature difference ratio in Embodiment 1. FIG.
FIG. 6 is a diagram showing a delay time due to turning off the fan in the first embodiment.
FIG. 7 is a diagram illustrating a delay time due to fan ON to OFF according to the first embodiment.
FIG. 8 is a graph showing the relationship between the fan output of the present invention and the battery-air temperature difference.
FIG. 9 is a diagram illustrating fan control according to the second embodiment.
FIG. 10 is a diagram showing a flowchart of the second embodiment.
11 is a graph showing characteristics of battery capacity and battery internal temperature according to Embodiment 3. FIG.
FIG. 12 is a flowchart of the third embodiment.
FIG. 13 is a diagram showing the relationship between fan output and air flow rate in a preliminary experiment of the present invention.
FIG. 14 is a diagram showing the relationship between the air flow rate and the heat transfer coefficient according to the preliminary experiment of the present invention.
FIG. 15 is a graph showing a relationship between a heat transfer coefficient and a temperature difference ratio between the inside and outside of a battery according to a preliminary experiment of the present invention.
[Explanation of symbols]
1 ... Battery 2 ... Junction box
DESCRIPTION OF SYMBOLS 3 ... Charger 4 ... Discharger 5 ... Controller 6 ... Fan 7a ... Battery temperature sensor 7b ... Air temperature sensor 8 ... Case

Claims (5)

The surface temperature of the secondary battery;
The blowing amount and blowing temperature of the fan for the secondary battery;
Internal temperature calculating unit of the secondary battery, characterized by calculating the internal temperature of the secondary battery from the inner and outer temperature difference ratio of the secondary battery by the air supply of the fan. Means for measuring the surface temperature of the secondary battery ;
Means for measuring the amount of air blown by the fan that blows air to the secondary battery;
Means for measuring the temperature of air blown by the fan;
Measuring means of the surface temperature of the secondary battery, the air volume of the measuring means, and includes a <br/> arithmetic should do arithmetic means the internal temperature of the secondary battery from the measured value by the blowing air temperature measuring means The internal temperature calculation device of the secondary battery according to claim 1, wherein 2. The secondary battery internal temperature calculation device according to claim 1, further comprising an on / off control means for the fan. 2. The internal temperature calculation device for a secondary battery according to claim 1, further comprising a control unit that primarily changes the blower output of the fan with respect to the measured value of the surface temperature of the secondary battery. 2. The internal temperature calculation device for a secondary battery according to claim 1, further comprising control means for controlling the blower output of the fan according to the capacity of the secondary battery.

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