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Battery Balancer: What To Balance And How

Jul 15, 2020

Different algorithms of battery balancing are often discussed when multiple serial cells are used in a battery pack for particular device. The means used to perform cell balancing typically include bypassing some of the cells during charge (and sometimes during discharge) by connecting external loads parallel to the cells through controlling corresponding FETs. The typical by-pass current ranges from a few milliamps to amperes. A difference in cell voltages is a most typical manifestation of unbalance, which is attempted to be corrected either instantaneously or gradually through by-passing cells with higher voltage.

In our work, we often meet customers asking what types of batteries are used by battery balancer? It can be applied to any battery, up to 18V per battery, 36V total.

The battery balancer equalizes the state of charge of two 12 volt batteries in series or multiple batteries in series. When the solar controller charging voltage of a 24 V battery system exceeds 27 V, the battery balancer is switched on to compare the voltage of two batteries connected in series. The battery balancer will get a maximum current of 1 ampere from the maximum voltage of the battery. The resulting charge current difference will ensure that all batteries move towards the same state of charge.

If necessary, multiple balancers can be connected in parallel. Three battery balancers balance the 48 volt battery pack.

By the way, many of our clients used BMV-700/702 battery monitor work with battery balancer together.