Lithium Ion, or Li-Ion, uses yet another charge algorithm. In this case, a constant current is supplied to the battery until the battery terminal voltage reaches 4.1 volts per cell. The charger then changes to a constant voltage source at 4.1 volts per cell, and the current tapers until it reaches 1/20 of the original constant current. The constant current, referred to as the bulk charge current is nominally set to the battery capacity divided by 2, and expressed in amperes. Figure 3 shows a Li-ion battery as it is brought from full discharge to full charge.

Figure 3