In one embodiment, a battery control system, comprising: a plurality of battery units comprising a battery system; and a controller coupled to the plurality of battery units, the controller configured to monitor, for each battery unit, a first voltage and a second voltage, the first voltage corresponding to an absolute value of a shut-off voltage and a second voltage corresponding to a warning voltage, the first voltage smaller than the second voltage, wherein responsive to one of the battery units reaching the second voltage, the controller is configured to provide a first alert before the any of the battery units reaches the first voltage.