Design Li-Po Battery Charger with Buck Converter under Partially CC-CV Method

A battery is a device that can store electricity. After being used as an energy source, the battery will decrease its energy capacity, so it can return to its maximum capacity again after the battery is recharged. The method commonly used to charge a Lithium Polymer (Li-Po) battery is a constant current constant voltage that is by giving a constant current first and continuing a constant voltage under certain conditions. To get the desired voltage, the Li-Po battery can be arranged in series connection. Arrangement of the batteries in series causes the time to charge each cell to be unequal because after use, each cell will have a different voltage. This paper proposes a Li-Po battery charger that can be used for charging each cell of the battery individually so that it does not cause overcharging of the battery cell. This Li-Po charger requires a buck converter with the constant current, constant voltage method (CC-CV). From implementation results, the proportional integrator (PI) controller in the buck converter can produce a constant current and a constant voltage at the resistive load, if the battery has a current ripple of 10% at constant current. The full battery charging test shows different times for each cell, for cell 1 for 84 minutes, cell 2 for 92 minutes and cell 3 for 76 minutes, with an average efficiency of 88.3% for converter 1, converter 2 for 89, 4% and converter 3 at 89.3%.