JPH11341698A - Electric vehicle charging device - Google Patents

Abstract

(57) [PROBLEMS] To provide a low-temperature power battery that can be easily and inexpensively heated and easily charged in an electric vehicle. A temperature T of a power battery in an electric vehicle
Is low, the charging current value for the battery is controlled to be low, as indicated by the current value curve II corresponding to the battery temperature curve I,
When the battery is energized, Joule heat is generated inside the battery to heat the battery, and the charging current value for the battery is controlled to increase stepwise as the temperature of the battery rises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power battery charging device for an electric vehicle.

[0002]

2. Description of the Related Art A power battery of an electric vehicle has a low outside temperature, so that when the temperature is low, a chemical reaction in the inside slows down. In particular, when an electrolyte is frozen, normal charging cannot be performed. In other words, the freezing of the electrolyte restricts the movement of electron ions and increases the internal electric resistance. Therefore, when charging at a constant current value as usual, the charging voltage increases and the upper limit value is easily increased. As a result, the protection circuit provided in the charger functions to stop the charging operation of the charger.

For this reason, at low temperatures, it is necessary to heat the battery with a heater or the like before the battery is charged to defrost the electrolyte, but in this case, the provision of the heater or the like requires a relatively large charging system. In addition, there is a problem that the equipment cost and the vehicle weight increase.

[0004] Further, a technology for detecting the temperature of a power battery in an electric vehicle and changing the current value for charging includes:
Japanese Patent Application Laid-Open No. Hei 9-46916 discloses a technique, but in this case, when the temperature of the battery is high, the charging current value is simply reduced to prevent the battery from deteriorating.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an electric vehicle for heating a low-temperature power battery very simply and inexpensively to activate the chemical reaction of the battery and thereby easily charge the battery. Is to try.

[0006]

Therefore, an electric vehicle charging apparatus according to the present invention has a first means for detecting a temperature of a power battery, and a first means for detecting a temperature of the power battery in accordance with a level of the temperature detected by the first means. And a second means for controlling the charge current value of the battery, wherein the second means decreases the charge current value as the temperature of the battery decreases, and decreases the charge current value as the temperature of the battery increases. It is configured to increase the value.

Therefore, the lower the temperature of the battery detected by the first means, the lower the temperature of the battery, the lower the battery temperature, the higher the internal resistance of the battery. However, the battery can be energized while limiting the increase in the charging voltage, and this energization causes the internal resistance of the battery itself to be used to generate heat from within the battery, thereby easily raising the temperature of a low-temperature battery. Becomes possible,
Further, the second means increases the charging current value of the battery as the battery temperature increases, so that the battery can be charged efficiently.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention shown in the drawings will be described below. In FIG. 1, an electric vehicle 1
Has a large number of power batteries 2 connected in series, and the electric output of the batteries 2 causes the motor 5 to rotate at an appropriate speed via the motor control device 3 and the inverter 4 so that the motor 5 drives the wheels 6. The battery 2 is driven and driven, and the battery 2 is provided with a temperature sensor 7 for detecting the temperature of the battery 2.

On the other hand, the charging device 10 includes a thyristor 11 connected to an AC power supply, a control circuit 12, a freezing estimating unit 13 connected to the control circuit 12, and an operation panel 1 respectively.
4 and a display panel 15, from the thyristor 11 to the connector 16 on the charging device 10 side and the vehicle-side connector 17
The DC current value supplied to the power battery 2 of the electric vehicle 1 via the control circuit 12 is controlled by the control circuit 12 as described later, and the temperature signal of the battery 2 detected by the temperature sensor 7 is input to the control circuit 12. .

The freezing estimating means 13 includes a storage circuit 18 and a comparing circuit 19, and estimates whether or not the electrolyte of the battery 2 is frozen based on the temperature signal of the battery 2 input from the control circuit 12. Alternatively, it is detected whether the temperature of the battery 2 is low enough to make charging extremely difficult, and the result is fed back to the control circuit 12.

Next, the operation of the control circuit 12 will be described. A temperature signal of the battery 2 constantly detected by the temperature sensor 7 and input to the control circuit 12 is supplied from the control circuit 12 to the freezing estimating means 13, and the freezing estimating means 13 freezes the electrolyte of the battery 2 or When the low temperature state of the battery 2 is fed back to the control circuit 12, the control circuit 1
2 corresponds to the temperature signal of the battery 2 from the point X on the battery temperature curve I in FIG.
The Y point on the current value curve II in FIG. 2 is extracted, and the DC current value supplied from the thyristor 11 to the power battery 2 of the electric vehicle 1 is controlled so that the charging current value Z indicated by the Y point is obtained. . FIG. 2 shows a good correlation between the temperature of the battery 2 and the charging current value from many experiments in which the relationship between the charging time and the charging efficiency of the battery 2 is considered.

That is, when the electrolyte of the battery 2 is in a frozen state, or when the battery 2 has a low temperature and the internal resistance of the battery 2 is large and it is difficult to normally charge the battery 2, the battery 2 is relatively low. Since the charging current of the value is supplied to the battery 2, the battery 2 can be energized while limiting the increase in the charging voltage. Heat is generated, and as a result, the electrolyte of the battery 2 can be thawed, or the temperature of the battery 2 at a low temperature can be increased.

As the temperature of the battery 2 rises, the control circuit 12 controls the battery 2 as shown by the current value curve II in FIG.
The thyristor 11 is controlled so that the DC current value supplied to the thyristor increases stepwise. When the temperature of the battery 2 further rises and reaches a temperature t at which normal charging is possible, the thyristor 11 is controlled. In the area a, charging with a constant current value and in the area b, charging with a constant voltage value and normal charging are efficiently performed.

In this case, the control circuit 12 controls the battery 2 in which the electrolyte is in a frozen state or the battery 2 in a low temperature state with Joule heat generated by energization, so that the battery 2 is heated. No separate heater or the like is required in particular, and the control programming in the control circuit 12 can be easily configured, so that the cost required for heating the battery 2 is low and the weight of the vehicle increases. There is an advantage that can be suppressed.

Further, since the internal resistance of each battery 2 is substantially the same, there is an advantage that the temperature of each battery 2 can be increased evenly. Further, the replacement of each battery 2 in the electric vehicle 1 is not required. Since it can be performed in the same manner as in the conventional case, it is very convenient in this aspect as well.

In the above embodiment, the charge current value for the battery is increased stepwise as the battery temperature rises, but this charge current value is increased steplessly as the battery temperature rises. It goes without saying that it may be done.

[0017]

In the charging apparatus for an electric vehicle according to the present invention, the charging current value of the battery is controlled to decrease as the temperature of the battery decreases, and the internal resistance of the battery itself is used by energizing the battery. To generate heat from inside the battery,
Since the temperature of the low-temperature battery can be easily raised, and no other device is particularly required for heating the battery, the cost required for heating the battery can be easily reduced and the weight of the vehicle can be suppressed from increasing. There are also great advantages that can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic wiring diagram according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric vehicle 2 Battery for power 7 Temperature sensor 10 Charging device 11 Thyristor 12 Control circuit 13 Freezing estimation means

Claims (2)

[Claims] A first means for detecting a temperature of the power battery; and a second means for controlling a charging current value of the battery in accordance with the level of the temperature detected by the first means;
The second means is a charging device for an electric vehicle, wherein the charging current value decreases as the temperature of the battery decreases, and the charging current value increases as the temperature of the battery increases. 2. The battery according to claim 1, further comprising: third means for detecting a frozen state of the battery from the temperature detected by the first means, wherein the frozen state of the battery is detected by the third means. A charging device for an electric vehicle, wherein the second means reduces the charging current value.