In some embodiments, the modification factor for a longest sustainable time duration corresponding to a discharge cut-off voltage may include a quotient of a common multiple of the longest sustainable time durations corresponding to different discharge cut-off voltages over the longest sustainable time duration corresponding to the discharge cut-off voltage. Correspondingly, the processor 51 may be further configured to calculate the common multiple of the longest sustainable time durations corresponding to different discharge cut-off voltages and the quotient; to use the quotient as a weight to weight the continuous discharge time duration corresponding to each of different discharge cut-off voltages; to sum the weighted continuous discharge time durations; to compare a summation result of the weighted continuous discharge time durations with the common multiple; and to perform a discharge protection on the battery in response to the summation result being larger than the common multiple. In response to the summation result being not larger than the common multiple, the processor 51 may continue to obtain the continuous discharge time duration of the battery being discharged at the discharge cut-off voltage until the summation result exceeds the common multiple and then the discharge protection can be performed on the battery.