I'm attempting to source replacement batteries for some medical devices (digital goniometer, inclinometer, etc.) The markings are:
GMB063048 3.7V 800mAh 2.0WH 2010.12.08 R
I've found batteries of suitable size and capacity (6mm x 30mm x 48mm, 850mAh). My issue is that the OEM batteries have a 3rd blue lead attached to a thermistor that is connected to a charging circuit on the main PCB.
All of the batteries I've been able to locate have only 2 leads. I find myself ignorant and frustrated here. Will I need to order a 2-lead battery and then simply connect the thermistor to the negative terminal in order to make this work, or is there a search term that I'm missing (being ignorant of battery configurations and features) that will help me locate what I'm looking for?
Thanks in advance for your advice and knowledge. I was raised by an electrical engineer, and consider myself an advanced hobbyist. I know very little about batteries, though.
My plan is to keep the existing thermistor and reuse it on a replacement LiPo cell. If it's too much trouble to explain why that's a terrible idea (if indeed it is), then a pointer to a resource I can use to teach myself the pertinent details would be fantastic.
Best Answer
If you are looking for replacement of a 3-pin 800 mAh Li-Po battery which is 8 years old, you need to look for something in the 1200 mAh range today. Because the Li-Po technology progresses. Here is an example from e-Bay:
Most of two-wire batteries are made cheap for RC (Radio-Controlled) toy applications. They have super-high discharge rates (15C to 90C) and can be harmful.
For individual replacement and for your private use you can do whatever it takes, but if you aim at industrial scale, consider all warnings in Olin's answer.
Actually, I have seen the opposite, an original China-made battery would came with three-wire connection form its BMS protecting circuit, but a European-based medical supplier re-packaged it with the yellow thermistor wire cut-off, making it a two-wire connector. So go figure the safety and reliability of this re-branding.
Your device will likely need the thermistor connection (usually PTC102, aka 10k to ground) to operate, otherwise the charger chip will sense a faulty battery (like most of Texas Instruments chargers would do, for example). You can re-use the old thermistor, or just fake it with corresponding chip resistor with a nominal value (10k at 25 deg.C, or whatever it is).
NOTE: there is an informal convention on pouched batteries dimensions. This one is labelled as "6043450", which means that it is 6.0 mm thick, 34 mm wide, and 50 mm long. Just FYI, you can use this as a search parameter to find a better fit.