US Patent 10199845 Electronic device

An electronic device includes an internal battery, a first battery, and a second battery. The device further includes a first latch for locking the first battery and a second latch for locking the second battery. The device further includes a latch state detector for determining whether each of the first and second latches are open or closed, and a remaining battery power detector for detecting the remaining power in each of the first battery, the second battery, and the internal battery. The device further includes an LED and an LED controller for controlling the on-off of the LED. The LED controller operates as follows when the first or second latch is determined to be opened. If at least one of the first battery, the second battery, and the internal battery can supply electric power to the electronic device, the LED controller lights the LED in a first ON state. If none of the first battery, the second battery, and the internal battery can supply electric power to the electronic device, the LED controller makes the LED light in a second ON state.