The constant current charging method is one of several charging methods for accumulators. In this method, the accumulators are charged with constant current over time. The current per time unit remains constant until fully charged.
To avoid overcharging, the charging process can be switched off after a set time. The charging time for fully discharged accumulators can be calculated from the nominal capacity, the charging current and the charging efficiency. This simple charging method with fixed charging time has some risks of overcharging. Therefore, in chargers with constant current charging method, the constant charging current is switched off when the final charging voltage is reached. Reaching the end-of-charge voltage is detected by the ratio of the voltage difference to the time difference (dU/dt).
In the case of charge termination detection according to the dU/dt quotient (differential equation: dU to dt), the voltage difference decreases the closer the charge voltage comes to the charge termination voltage. The voltage changes per time unit decrease until full charge is reached. At full charge, the voltage difference no longer occurs, dU/dt mathematically becomes zero and reverses. This means that the maximum has been reached and the charging voltage can be switched off.
The constant current charging method is also available in a pulsed version as pulse charging method.