Daily maintenance and charge-discharge test of battery in photovoltaic power station

4. Battery charge and discharge test

(1) Purpose of battery charge & discharge test

Through regular charge and discharge tests on the battery pack, its performance can be improved, the capacity can be stimulated, the service life can be extended, and faulty batteries can be found and dealt with in time to prevent the problem from expanding.

(2) Satisfy the conditions of regular charge and discharge test

1. The battery has been left unused for more than three months;

2. The floating charge voltage of the single battery is lower than 2.18V;

3. The battery discharges more than 15% of its rated capacity;

4. The battery has been running for more than one year in floating charging state;

5. After replacing some batteries with low capacity;

6. The battery should be checked and discharged once a year, releasing 40-50% of the rated capacity;

7. The battery should undergo a capacity test every 3 years, and release 80% of the rated capacity.

(3) Battery charge and discharge test plan

1. First discharge the battery pack at a constant current of 0.1C10. If the voltage of a single battery drops to 1.8V, stop the discharge;

2. Then carry out 0.1C10 constant current charging, and when the average cell voltage rises to 2.25-2.35V, it will turn into a floating charging state.

(4) Discharge current and time

1. The discharge adopts the resistance constant current method, and the discharge current does not exceed the current rate of 10 hours. Taking the battery capacity of 200Ah as an example, the discharge current is 0.1C10, which is 20A; 2. Discharge time: calculated by releasing 40% of the rated capacity, t=40%*200/20=4h; 3. Charge immediately after discharge, and cannot be left on hold.

(5) Daily operation mode of DC system

1. The charger module and the battery run side by side on the DC bus;

2. The 400V AC power supply supplies power to all loads on the DC bus through the charging module, and at the same time float charges the battery.

(6) Specific implementation steps of charge and discharge test

1. Connect the battery discharge interface terminal to the DC input terminal of the battery discharge device through the connecting wire (please pay attention to the positive and negative poles when wiring).

2. Check the charging module and DC bus voltage are normal.

3. Disconnect the battery switch on the charging screen and stop the floating charging operation of the battery (the battery pack is set to no-load state).

4. According to the DC panel monitoring device, check the DC bus voltage, battery pack voltage, and single battery voltage, and use a multimeter to retest and verify, and make relevant records.

5. Purge the battery pack.

6. Close the battery discharge switch, switch the DC switch of the battery discharge device, check that the screen display of the battery discharge device is normal, and set the parameters (discharge current: 20A, discharge time: 4 hours). After checking that the wiring is correct and the parameter settings are normal, press the start button of the battery discharge device to start discharging the battery.

7. Constant current discharge: During the constant current discharge process, record the discharge current, battery pack voltage, activation capacity, terminal voltage of each single battery (measured by a DC monitoring device or a multimeter), and the shell temperature of the single battery once every hour during the constant current discharge process. If it is found that the voltage of a single battery drops to 1.8V (end voltage) during the discharge process, the battery with a voltage less than 1.8V is considered to be short of capacity, stop discharging, record the discharge time, and check the capacity of the battery pack voltage after discharge .

8. After the discharge is completed, disconnect the battery discharge switch and remove the load line.

9. Close the battery switch on the charging screen to start charging the battery.

10. Constant voltage charging: constant voltage equalizing charging (current limiting): when the ambient temperature is 25°C, the charging voltage of a single battery is 2.35V, and the charging voltage of a battery pack is 2.35V×104=244.4V, and the charging current is not specified , but limited to I≤30A (1.5×20=30). If the battery performance is good, the charging current should be around 20A.

11. During the charging process, record the charging voltage, charging current, battery pack voltage, and terminal voltage of each single battery every hour, and check the appearance of each battery for abnormalities.

12. Float charge: As time goes by, the equalized charge current gradually decreases. When the equalizing charging current is ≤2A (0.01C10), it should automatically turn to the float charging state. At this point, the regular charge and discharge for activating the battery is over.

13. After automatically switching to floating charging, record the charging voltage, charging current, battery pack voltage, terminal voltage of each single battery, and the temperature of the single battery shell again.

(7) Matters needing attention in test implementation:

1. There must be a special person to record the meter reading during the battery activation process, and there must be a special person to monitor during the charging and discharging process;

2. During the charging and discharging process of the battery, the doors and windows of the battery room should be kept open as much as possible to maintain ventilation;

3. During the charging and discharging process of the battery, fireworks are strictly prohibited on site, and fire extinguishers must be placed on the test site.

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