Disclosed herein are system, method, and computer program product (computer readable medium) embodiments for extending battery longevity by improving partial-state-of-charge operation of batteries. An embodiment operates by determining, using at least one processor, that at least one first battery has stopped charging at a partial state of charge, in which the at least one first battery is associated with a first battery bank and is rechargeable, and charging, in response to receipt of a command issued from the at least one processor or another processor in response to the determining, the at least one first battery using at least one second battery, in which the at least one second battery belongs to a second battery bank that is not the first battery bank, by transferring charge from the at least one second battery to the at least one first battery.