For a lithium battery pack including battery cells the number of which is larger than the number of battery cells 111 that can be monitored by a voltage detect portion 115, there is disposed a temperature detect element 113 for detecting the temperatures of the battery cell 112 not monitored by the voltage detect portion 115, and, when the temperatures of the battery cell 112 detected by the temperature detect element 113 rise beyond a given value, there is issued a signal to stop the charging of the battery pack.