The cover lifts off, exposing the eighteen 3/4A NiMH cells inside.

The device on top, with the black and white wires, is a thermistor for sensing the temperature of the pack.

There are two safety devices (not shown) which connect in series with each of the two series strings of cells. They are Klixon 4MM75A-21 overcurrent/overtemperature protection devices which use a bimetallic strip to break the circuit.