Research on performance test of intelligent battery charger

Abstract: This paper introduces the principle of constant voltage electronic load and its application in the performance test of intelligent battery charger.

The load is an indispensable testing instrument for the development of intelligent battery chargers.

Keywords: Electronic load intelligent charger research

Development of Characteristic Test of Intellectual Battery charger

Abstrsact: This Paper introduces theory of constant voltage electric load and characteristic test of intellectual battery charger,and thinks it must has constant voltage electric load for developing intellectual battery charger.

Keywords:Electric load Intellectual bsttery charger Study

1 Introduction

As we all know, to ensure the normal life of the battery, it is necessary to provide the battery with an acceptable and scientific charging current. Smart chargers are developed in this context. Whether a smart battery charger has reached the design specifications can theoretically be tested with real secondary batteries, but this method is a lengthy and difficult process, which is not in line with the actual situation in research and production. Constant voltage electronic loads can solve this problem well.

2. Development of Constant Voltage Electronic Load

2.1 Principle of constant voltage electronic load

An electronic load is a power supply test instrument that uses high-power semiconductor devices to absorb the current provided by the power supply and convert it into heat energy to simulate the load. The working principle of the constant voltage (CV) electronic load is shown in Figure 1. It absorbs enough current from the power supply to control its output voltage to reach the set value, so it can simulate the terminal voltage of the battery and can quickly and accurately test the output characteristics of the smart battery charger. In addition, it can also be used to test the current limiting characteristics of the power supply.

(a) Principle of electronic load (CV) (b) Output characteristics

Figure 1 Principle and output characteristics of electronic load

2.2 Development of constant voltage electronic load

The schematic diagram of the JTU-100 electronic load is shown in Figure 2. It can absorb a maximum current of 10A. In the figure, V1 and V2 are adjustment tubes, Uref is an adjustable reference source, and 1 and 2 are output terminals. By adjusting the size of Uref, the set voltage can be obtained at terminals 1 and 2 regardless of how the load changes.

Figure 2 Schematic diagram of JTU-100 electronic load

3. Performance test research of intelligent battery charger

Figure 3 is a block diagram of a developed intelligent battery charger, which meets the charging requirements of 12V VRLA batteries under cyclic use conditions. The design indicators are:

Figure 3 Schematic diagram of the smart battery charger

(1) When Ub≤14.2V, constant current charging is performed with a charging current of 2A.

(2) When Ub>14.2V, the charging current decreases linearly with the increase of battery voltage.

(3) When Ub ≥ 15.5, the battery is charged with a current of about 10 mA to compensate for the self-discharge current of the battery.

(4) The temperature compensation coefficient of the charging threshold voltage is -23mV/℃ (12V VRLA battery)

The test steps are as follows:

①Connect the power supply to the JTU-100 electronic load and adjust the output to 13.5V.

②Connect the wires as shown in Figure 4.

③ Turn on the switch of the electronic load first, then turn on the switch of the smart battery charger. The ammeter shows 2A and the voltmeter shows 13.5V.

④ Gradually increase the output voltage of the electronic load. When the voltage is greater than 14.2V, the output current gradually decreases. When the output voltage of the electronic load rises to 15.5V, the current drops to about 10mA.

⑤ Gradually reduce the output voltage of the electronic load, and the ammeter reading increases linearly. When the output voltage is less than 14.2V, the ammeter reading increases to 2A and remains unchanged.

⑥ In order to test whether the temperature compensation of the charging threshold voltage meets the design index, the temperature sensor of the smart battery charger is placed in a constant temperature box to measure the charging curve at that temperature. The measurement results are shown in Figure 5.

4 Conclusion

The emergence of electronic loads will promote the further development of power supply technology. Constant voltage electronic loads are indispensable testing instruments for the development of intelligent battery chargers.

Figure 4 Battery charger test wiring diagram

Figure 5 Charging curves at several temperatures