Electric Vehicle Charger Precautions

Constant Voltage Charging: Constant voltage charging refers to charging each individual battery cell at a constant voltage (generally the number of cells × 2.5V). Its main characteristics are: a relatively large current at the beginning of charging, resulting in a rapid increase in battery electromotive force and electrolyte relative density; the charging current gradually decreases as charging continues, with only a small current flowing at the end of charging; short charging time and low energy consumption; generally, the battery can obtain 90%–95% of its capacity after 4–5 hours of charging; if the charging voltage is properly selected, the entire charging process can be completed in 8 hours, and no human intervention is required during the entire charging process, making it widely used for supplementary charging.

Constant Current Charging: Constant current charging refers to charging the battery using a segmented constant current method, where the current is adjusted by regulating the charging device. Its main characteristic is its greater adaptability, allowing for arbitrary selection and adjustment of the charging current. Therefore, it can charge batteries in various conditions and states (such as initial charging of new batteries, supplementary charging of used batteries, and desulfation charging). It is particularly suitable for charging battery packs consisting of multiple batteries connected in series using a low-current, long-duration charging mode, and is beneficial for charging batteries with slow capacity recovery.

However, because the charging current is too small at the beginning and too large in the later stages, the entire charging process is lengthy, produces a lot of gas, causes significant impact on the plates, has high energy consumption, and low efficiency (not exceeding 65%). Furthermore, the entire charging process requires close supervision. Therefore, it is only used for the initial charging of batteries and when a long-term, low-current desulfation charging process is needed.

Equalization Charging

For battery packs composed of many individual cells, such as stationary batteries, equalization charging should be performed periodically after a certain period of operation. This is because when charged under the same conditions, the active materials in different parts of the plates will have varying degrees of charging, resulting in an uneven reaction. Additionally, considering the differences in charge-discharge characteristics between individual cells, some cells may be undercharged. Therefore, after the normal charging is completed, a further charging at a rate of approximately 20 h⁻¹ for 1-3 hours is performed. This type of charging is also called overcharging. Regular equalization charging is beneficial for battery maintenance when batteries are used under the same conditions.

The interval between equalization charges varies among users; some recommend every three months or six months. However, due to advancements in battery design and manufacturing technology, the characteristics of batteries are becoming less differentiated, thus there is a trend towards extending the interval between equalization charges.