Multilevel Converters are studied for simultaneous_x000D_ use as a DC-motor drive active battery cell balancer._x000D_ The Multilevel Converter (MLC) allows to independently switch_x000D_ ON/OFF each battery cell in a battery pack giving the possibility_x000D_ of non-uniform use of the battery cells. By exploiting this_x000D_ property brake regeneration phases in the drive cycle, the_x000D_ MLC has the possibility to balance both State-of-Charge (SoC)_x000D_ temperature differences between the cells, which are two_x000D_ known causes of battery wear, without even reciprocating the_x000D_ coolant flow inside the pack. The optimal control policy (OP )_x000D_ that takes into consideration both the battery pack temperature_x000D_ SoC dynamics is studied in detail based on the assumption_x000D_ of perfect information of the state the future driving. The_x000D_ results show that OP gives significant reduction in temperature_x000D_ SoC deviations compared to uniform use of all the cells even_x000D_ under unidirectional coolant flow. Thus reciprocating coolant flow_x000D_ is a redundant function for MLC based cell balancer. A specific_x000D_ contribution of the paper is the derivation of a state-space electrothermal_x000D_ model of a battery submodule €”for both unidirectional_x000D_ as well as reciprocating coolant flow€” under the switching action_x000D_ of an MLC, formulated in such a way that the OP is given by_x000D_ the solution of a convex optimization problem._x000D_