JPH06217415A - Battery charger for electric vehicle - Google Patents

Abstract

PURPOSE:To provide a battery charger for electric vehicle in which charging time can be shortened significantly without causing any damage on the battery. CONSTITUTION:A liquid temperature detecting means 5 detects the liquid temperature of a battery 3 for electric vehicle and charging current control means 6, 7 feedback control the charging current of the battery 3 according to the liquid temperature of the battery 3 thus sustaining the liquid temperature in the vicinity of highest allowable level. This constitution allows constant charging of the battery 3 with maximum charging current within the highest allowable liquid temperature determined by the service life of battery and the like and ending the charging operation within a shortest time while avoiding problems caused by liquid temperature rise, e.g. shortening of the service life of battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger for an electric vehicle.

[0002]

2. Description of the Related Art In conventional battery charging, a charging method that keeps a terminal voltage of a battery constant during charging, a charging method that keeps a charging current constant, and the like are known.

[0003]

In recent years, there has been a strong demand for practical use of electric vehicles, and various developments have been made. However, the problem with electric vehicles is that the charging power of the battery is small, and they are frequently used. Charging is required. Therefore, it is necessary to arrange many charging stations along the road, but if the charging time per unit is long, the number of processing units per unit time of each charging station will decrease, and
Problems such as forcing the driver to be patient. However, in the above-mentioned constant voltage or constant current charging, if the charging current is increased, problems such as boiling of the electrolyte and shortening of battery life will occur under adverse conditions such as hot weather in midsummer.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery charging device for an electric vehicle capable of significantly shortening the charging time without damaging the battery. It is an issue.

[0005]

A battery charging device for an electric vehicle according to the present invention includes a liquid temperature detecting means for detecting a liquid temperature of an electric vehicle battery, and a charging current fed to the battery is feedback-controlled by the liquid temperature. However, a charging current control means for maintaining the liquid temperature near the maximum allowable liquid temperature of the battery is provided.

In a preferred mode, the charging current control means is mounted on a vehicle. In a preferred aspect, the charging current control means is arranged in a charging station on the ground side.

[0007]

The liquid temperature detecting means detects the liquid temperature of the battery for the electric vehicle, and the charging current control means feedback-controls the charging current supplied to the battery by the liquid temperature, so that the liquid temperature is the maximum of the battery. Maintain near the allowable liquid temperature. By doing this, the maximum charging current can always be applied during battery charging within the range that does not exceed the maximum allowable liquid temperature determined by the battery life, etc. It is possible to complete the charging in a minimum charging time while avoiding the problem that occurs.

[0008]

(Embodiment 1) An example of an electric vehicle battery charger of the present invention will be described below with reference to FIG. This device is an inverter 1 that is supplied from a 200 V power source of commercial frequency and outputs a high frequency voltage of several tens of kHz.
And a full-wave rectifier 4 for full-wave rectifying the high frequency voltage received from the inverter 1 through the gap transformer 2 to charge a vehicle driving battery (electric vehicle battery) 3.
A temperature sensor (liquid temperature detection means) 5 for detecting the liquid temperature of the battery 3, a controller (a part of the charging current control means in the present invention) 6, a high-level output terminal of the full-wave rectifier 4 and a high-level battery. A power MOS transistor (remaining part of the charging current control means in the present invention) 7 connecting to the end is provided.

The gap transformer 2 has a primary coil 21.
Has a primary core 22 wound around it, and a secondary coil 24 has a secondary core 24 wound around it. The circuit is configured such that the primary coil 21 is fed from the inverter 1 and the secondary coil 23 is fed to the full-wave rectifier 4.

The temperature sensor 5 is a thermistor type temperature sensor immersed in the liquid tank of the battery 3, and the detected temperature signal voltage is input to the controller 6. The controller 6 has a microcomputer configuration, and intermittently controls the power MOS transistor 7 based on the temperature signal voltage to perform feedback control of the charging current to the battery 3 so that the liquid temperature is the maximum allowable liquid temperature of the battery 3 (in this embodiment, 60 ° C.).

The control operation of the controller 6 will be described below with reference to the flowchart of FIG. However, it is assumed that both cores 22 and 24 of the transformer 2 are joined and the inverter 1 is supplying a high frequency current. First, the controller 6 is supplied with power from the battery 3 by turning on the key switch, and initialization is performed (100). Next, it waits until a charging start switch (not shown) provided in the electric vehicle is turned on (102), and by inputting an ON signal of the charging start switch, the stored current value Im is read from the current value storage register, and this storage is stored. Let the current value Im be the control current I (1
04). At this point, since it is the beginning of the routine circulation, a predetermined initial current value Io is set in the current value storage register in step 100, and therefore the control current I becomes Io.

Next, the intermittent duty ratio of the power MOS transistor 7 corresponding to the control current I searched in step 104 is searched, and the power MOS is searched at this duty ratio.
The transistor 7 is turned on and off (106). As a result, the battery 3 is charged with the control current I (here, the initial current Io). Next, the input from the temperature sensor 5, that is, the liquid temperature T of the battery 3 is read, and the liquid temperature T is a predetermined maximum allowable temperature Tm.
Check if it is less than ax (60 ° C here) (10
8) If so, a predetermined current increment ΔI is added to the memory current value Im (110), otherwise, the memory current value Im.
From the above, a predetermined current decrease amount ΔI is subtracted (112), and the routine proceeds to step 114.

In step 114, the terminal voltage of the battery 3 (when the power MOS transistor 7 is off) is detected, and it is determined whether the terminal voltage has reached a predetermined end-of-charge voltage (a value close to the full-charge voltage). If it has not been reached, the routine returns to step 104 to repeat the routine. If it has been reached, the memory current value Im is set to the predetermined end-of-charge current value Ie (116), and the routine proceeds to step 118.

At step 1118, the battery voltage at step 114 is the end-of-charge voltage (a value close to the full-charge voltage).
It is checked whether or not the elapsed time has reached a predetermined time, and if so, this charging operation is terminated, and if not reached, the routine returns to step 104, and the charging current is charged at the duty ratio corresponding to the stored current value Im. Control intermittently. In this embodiment described above, the following operational effects can be obtained.

First, since the liquid temperature T detected by the temperature sensor 5 is charged at the maximum charging current in a range not exceeding the maximum allowable temperature, the charging time can be greatly shortened and the number of processing stations at the charging station can be greatly increased. It also makes it possible to reduce the waiting time for charging the driver. Further, it is possible to avoid problems such as shortening of battery life due to excessive rise of the liquid temperature T. Temperature sensor 5, power MOS transistor 7 and controller 6
Since the charging current control means consisting of is installed in the electric vehicle, cable routing for transmitting the detection signal of the temperature sensor 5 to the charging station side can be performed as compared with the case where the charging current control means is provided on the charging station side. No connector connection required.

At the end of charging, a predetermined end-of-charge current value Ie
Since the battery is charged at, the effect of stirring the battery liquid can be obtained. Of course, it is also possible to arrange the charging current control means on the charging station (ground) side, and the temperature sensor 5
It is also possible to provide each on the charging station (ground) side and insert it into each battery one by one. It is also possible to provide the inverter on the vehicle side.

Further, in the above embodiment, the inverter 1 was used to increase the frequency, but it is naturally possible to supply power at a commercial frequency or DC power. Although power was supplied by the transformer 2, it is naturally possible to use a connector.
Further, instead of controlling the charging current by switching the power MOS transistor 7, it is naturally possible to switch the tapped transformer.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the controller of FIG.

[Explanation of symbols]

 3 battery (battery for electric vehicle), 5 temperature sensor (liquid temperature detecting means), 6 controller (charging current control means), 7 power MOS transistor (charging current control means)

Claims (3)

[Claims] 1. A liquid temperature detecting means for detecting a liquid temperature of an electric vehicle battery, and feedback control of a charging current supplied to the battery by the liquid temperature so that the liquid temperature is in the vicinity of a maximum allowable liquid temperature of the battery. A battery charging device for an electric vehicle, comprising: a charging current control unit that maintains the charging current. 2. The battery charging device for an electric vehicle according to claim 1, wherein the charging current control means is mounted on a vehicle. 3. The battery charging device for an electric vehicle according to claim 1, wherein the charging current control means is arranged in a charging station on the ground side.