A Third Wire?

[metrologist]

A friend asked me to fix his brand new electric kick scooter with an alleged battery issue. I removed the battery pack for inspection and discovered it is made from 12 D-size NiMH batteries, 10,000 mAh.

It has a medium size 3rd wire coming out of the pack and I wonder what it's for? I'd like to just hook up my hobby charger (like the one that Dave reviewed) and cycle it a few times, but not sure...

[Zero999]

It's most likely a temperature sensor, probably a thermistor. As it's only one wire, rather than two, the other connection will be one of the battery terminals, most likely the negative.

[metrologist]

Makes sense. I was also thinking of just using a 4s Lipo pack. Most of the RC car packs are very high discharge, like 20C to 30C (200+ Amps  ). Would they still work OK for this application? I think the NiMH were rated a mere 30 Amps, so the scooter probably does not draw that much current.

[CatalinaWOW]

My sons have done these LiPo conversions successfully.  Just make sure that whoever is using the scooter is aware of the proper care and feeding of LiPo batteries.  They can't be treated as casually as the regular batteries.  Most people just mistreat whatever battery is in these scooters, which is why they are so often found dead.