Electric Vehicle Charger - Constant Voltage Charging

Constant voltage charging means that each single cell is charged at a certain constant voltage (generally, the number of cells is taken as × 2.5V). Its main characteristics are: the current at the initial stage of charging is quite large, the electromotive force of the battery and the relative density of the electrolyte rise rapidly, the charging current gradually decreases with the continuation of charging, and only a small current passes through at the end of charging; The charging time is short and the energy consumption is low. Generally, the battery can obtain 90% ~ 95% of its capacity after charging for 4 ~ 5h; If the charging voltage is properly selected, the whole charging process can be completed in 8h, and the whole charging process does not need human care, so it is widely used for supplementary charging.

The disadvantages of constant voltage charging are that the initial charging current is too large, and the initial charging current will rise sharply when charging the battery with excessive discharge depth, which is easy to cause overcurrent of the charged battery and damage to the charging equipment; During the charging process, since the charging current cannot be adjusted, it is not applicable to the initial charging and desulfurization charging of the battery; Since it is difficult to compensate for the change of the battery voltage during the charging process, it is difficult to complete the full charge of the battery with slow capacity recovery.

The following matters shall be noted when using constant voltage charging method:

① Select the charging voltage correctly. If the charging voltage is too high, it will cause excessive charging current at the initial stage of charging, and in serious cases, it will cause bending of the electrode plate, a large number of active materials falling off and excessive temperature rise of the battery. If it is too low, the battery will be under charged, resulting in reduced capacity and shortened service life;

② The terminal voltage of the charged battery must be the same.