Individual cell balancing on multiple packs
There are two possibilities for how balancing is done depending on the pack architecture.  If the pack is 4 series, each one composed of 4 parallel cells, then no balancing is required for the cells in parallel.  They are directly connected together and cannot get out of balance.



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If you have 4 strings of 4 cells, each string is 4 cells in series and the 4 strings are in parallel, then you need a balance controller for each of the strings.  This pack architecture has no real advantage over the standard 4s4p unless the strings can be isolated (you get some tolerance for cell failures in this case).  With this architecture you have to be very careful about balancing.



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