I have a NiMH battery pack that needs replacing in a tv terrestrial field strength meter. The pack is 6 cells and is rated at 7.2v 2500mAh. It has 2 pairs of 2 wires so 4 wires that connect to 2 plugs on the internal board. I have opened up the pack. two of the wires are on the outside of the pack and not physically connected. I'm guessing it's some sort of sensor and if so can I just remove it and add it to another pack that doesn't have one? It doesn't appear to be connected directly in any way. I have seen similar packs but they only have the usual 2 wires.
Best Answer
That is a temperature sensor. You should reattach it in the new pack, firmly pressed against the cells by the tape.
It is difficult to detect electrically when a NiMH battery is fully charged. One standard technique is to watch for a temperature rise, because once the battery is charged the input energy will be converted to heat instead of stored.
Other packs you have seen without a temperature sensor may be used with chargers which trickle charge (charging so gently that continuous overcharge does not damage the cell) or look for signs in the change of voltage over time, as described in the linked article.