LiPo battery question

Jan 03, 2023 Last reply: 3 years ago 5 Replies

My daughter has some headphones with a rechargeable battery that is losing capacity.



It’s a small thing of 180mAh capacity and while there are plenty of similar batteries on eBay, they all just have two wires, whilst hers has three (red, black and white). Three wire batteries seem to be more common in the larger battery sizes.



My daughter wants to know what the third wire does and can she fit a two wire one instead?



Best solution would obviously be to find one with three wires if possible. I’ve only looked on eBay so far. Any other suggestions for places to look?



Tim


It's normally an NTC thermistor for sensing the battery temperature. The battery management will cut the power if it senses it's overheating.

Searching around, one ref suggests it's a 10K NTC thermistor with a beta of

3977K, but I can't find confirmation that's a common spec. I'm guessing it's between the third terminal and the negative pole, but haven't confirmed that.

You could try measuring the old one at different temperatures and from that there are online calculators to calculate the beta.

Aliexpress?

Theo

Three wires implies some more intelligence in the charger. It can be monitoring of heat for example. I don't really want my ear to catch fire due to the circuit malfunctioning!

Brian

Do the company who made the phones have a UK distributor? How old is the unit? Brian

It depends. A two cell RC LIPO battery has a three wire charging connector in order to charge each cell separately, in case they become unbalanced, when one cell may get overcharged.

Not saying this is the case here, but its possible.

Pretty sure Big Clive did a strip down of a 3 contact battery on his YouTube channel

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