The constant current charging method charges the battery with a steady current. Like the constant voltage method, when the battery is fully charged, the charger must switch to float charging mode to prevent damage from overcharging. Compared to constant voltage charging, this method can fully charge the battery quickly.
However (quoting you): charging at a constant voltage (say 4.2V) so long as the maximum current is limited to a reasonable value for the cell means you will have constant current charger till your cell is at ~95%. Up to this point the voltage across the battery will be less than 4.2V if you measure it.
So as charging continues at a constant voltage, the charging current decreases due to the decreasing potential difference between the charger-output voltage and the battery terminal voltage as the battery charges. Expressed differently, the charging current is highest at the beginning of the charge cycle and lowest at the end of the charge cycle.
The current will remain constant until the voltage rises to 28V. At this point the power supply will transition to constant voltage mode and the current will decay to zero when the battery is fully charged. The charge current is controlled to avoid overheating and the float voltage limited to avoid over-charging.
There are three common methods of charging a battery: constant voltage, constant current and a combination of constant voltage/constant current with or without a smart charging circuit. Constant voltage allows the full current of the charger to flow into the battery until the power supply reaches its pre-set voltage.
Importantly, the DC power source ensures that it does not exceed the maximum battery voltage limit during this adjustment. The relationship between the charging voltage and the battery charging current limit can be expressed by the formula: Charging voltage = OCV + (R I x Battery charging current limit) Here, R I is considered as 0.2 Ohm.
In a battery, the number of protons and electrons in the system are fixed, causing a constant voltage that varies with the charge of the battery.As the electrons flow from one terminal to the other, the voltage drops because there are less free …