3/27

LOW-COST DOUBLE LI-ION BATTERY CHARGER USING ST6255C/ST6265C MCU

1 THEORY OF OPERATION

1.1 BATTERY CHARGING

Li-ion batteries have a very different charging procedure from NiCd or NiMH batteries. Li-ion

constant current.

Figure 1. Li-ion Charging Method

During Stage 1 (constant current charge), the charging current is kept at a constant value

suffer significant damage if this final voltage is exceeded. Then, in Stage 2 (constant voltage

charge), the voltage is kept constant within this limit by slowly decreasing the current.

Charging is stopped when the current drops below the manufacturer fixed threshold value

Battery

voltage

t

t

Battery

current

Stage 1

Stage 2

2