The ATmega32HVB contains internal cell-balancing FETs. Cell balancing is controlled by the internal registers and will enable a FET between NV, PV1, PV2, PV3 and PV4 on SB202. The cell balancing current must be limited with the series resistors R12, R13, R15, R16 and R17 and must be in the range specified in the ATmega32HVB datasheet.