Comparison of Balancing Methods for LiPo Cells Energy Storage at Medium Power Ratings

This paper presents the comparison between two balancing methods: Active balancing using a Buck-Boost Converter and Passive Balancing by resistance switching. The active balancer was realized using a DC-DC Converter, which is operated by a Peak Current Control (PCC). This allows the inductor current to be tracked to reduce or increase the voltage to be spread over a pair of cells. The Passive balancer works with a switching resistor which allows to transform the voltage excess of each battery, in form of heat, being the resistance controlled by a microcontroller while carrying out the balancing of two cells. Both methods balance the voltage of the cells and are intended to properly work with a couple of LiPo cells and a nominal voltage of 3.7 V and 16,000 mAh connected in series. The two battery balancers were constructed and experimentally verified by measuring the rolling time of the cells, comparing cost and manufacturing times to identify experimentally the advantages of this group of cells and use the most suitable method to reach the prototype to a 5.6 kWh energy rating for an 83 kW electric motorbike vehicle.