By Irena Zhuravchak and Volodymyr Ilchuk | Tuesday, June 27, 2023 Charging a battery using the constant-current/constant-voltage (CC/CV) method involves using the constant current in the initial state of charging and then switching to constant voltage in the later stages of charging, when the battery reaches the set charge level.
There are four commonly used and popular charging methods: CC charging is a simple method that uses a small constant current to charge the battery during the whole charging process. CC charging stops whena predefined value is reached. This method is widely used for charging NiCd or NiMH batteries, as well as Li-ion batteries.
Generally, the CV charging method is efficient for speedy charging, but it damages the battery capacity. The negative effect is caused by an increased charging current at a low battery SOC (at the beginning of the charging process), where the current value is significantly higher than the nominal battery current.
In CV mode, charging is carried out by maintaining the voltage at the cut-off threshold, and then the current decreases. The charging process will be terminated when the current reaches a particular value (usually 0.02 C or 0.052 A) since the battery is considered fully charged.
OCV is an estimation of battery SoC by calculating the battery’s open-circuit voltage (voltage when the battery current is zero). The basic formula for the OCV method can be seen in (2) , where A0 is the terminal voltage at SoC = 0% (Vmin).
The charging process would be continued until the charging voltage reached the fourth cut-off at 8.54 V, with a current of 0.52 A. At the fifth step of the charging strategy, the voltage would be maintained to stabilize the charging current at 0.52 A until the battery became fully charged.