Nowdays electrical energy storage devices are getting more important. Currently Li-ion batteries are used widely because of their outstanding power density, specific energy and low cost. Li-ion batteries can be found in many machines and devices such as electric cars, mobile phones, tablets, laptops, RC models.
High power and high capacity battery packs contain multiple battery cells connected in series and/or in parallel.The rated capacity of the battery pack can only be utilized if all battery cells connected in series have same charge level. The device which can achieve charge equalization is called battery balancer. Passive balancing might be slow and generates a large amounth of waste heat. Quick balancing and high efficiency is highly important in many applications, and this cases require active balancing.
Modern balancing techniques will be summarized in this paper. Design of an active balancing system will be presented in details. The correct operation will also be demonstrated by efficiency measurements.