Charging System Design

Lithium ion batteries must use "Constant Current /Constant Voltage (CC/CV)" charging method. First the battery is charged till it reaches a set voltage by using a set constant current and then charged with this constant voltage till the current is below 0.02C.

Lithium ion batteries have charging voltage and current limits. The terminate voltage tolerance should not be over 1%. For a single cell the max charging voltage is 4.2±0.042V. For a multi-cell battery pack the maximum terminate charging voltage is 4.2Vx N (N: the number of series cells).

The charging current is to be in the range of 0.2C~1C ( C means the nominal capacity of the battery, if 1C=800mAh, 1C charge means 800mA charge current). Big current charging can results in battery over heated even explosion.

If charged exceeding this limit, the batteries will be permanet damaged. So the charge must be strictly controlled. It needs a high precise circuit to safeguard the charging. In designing charging system special considerations are necessary to ensure the battery can be both fully charged but at the same time not overcharged.

Correct charging system is critical to battery performance such as running time and cycle life. All CREUP charging designs for lithium ion batteries apply typical constant-current and constant-voltage controlled charging system. We use the world best charging circuit components to monitor or control the current and voltage statues accurately.