Methods and systems are provided for optimizing usage of a large number of battery cells, some, most or all of which are fast charging cells, and possibly arranged in battery modules—e.g., for operating an electric vehicle power train. Methods comprise deriving an operation profile for the battery cells/modules for a specified operation scenario and specified optimization parameters, operating the battery cells/modules according to the derived operation profile, and monitoring the operation of the battery cells/modules and adjusting the operation profile correspondingly. Systems may be configured to balance cell/module parameters among modules, to have parallel supplemental modules and/or serial supplementary cells in the modules, and/or have supplemental modules and circuits configured to store excessive charging energy for cells groups and/or modules—to increase the cycling lifetime and possibly the efficiency of the systems. Disclosed redundancy management improves battery performance and lifetime.