BATTERY SYSTEM

A battery system includes a power bus and a set of battery packs. A battery pack is one or more batteries, a sensor board, and a power board. The power bus is used to electrically connect the set of battery packs. The sensor board receives a voltage difference between a battery pack not connected to the power bus and the power bus; determines whether the voltage difference indicates that a battery pack voltage is too high compared to a power bus voltage; in response to determining the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, provides a drain indication to drain off the battery pack using a power draw mechanism until the voltage of the battery pack is within a threshold voltage difference of the power bus; and provides a connect indication to connect the disconnected battery pack to the power bus.