Simple Battery Question

Heya VHS,

So I have a simple battery question,

My wireless mouse has been having charging issue, and it’s not really an item that’s made to be easy to fix, but I just cracked it open and gotten the battery out. This is what I found!

It seems like it is indeed a bit swollen to me, kinda oval shaped for a battery. According so someone online, these are the OG batteries.
https://www.lithiumpolymer-battery.com/quality-11131562-rechargeable-401846-lithium-polymer-cells-3-7v-1000mah-lithium-ion-polymer-battery

So I’ve just tried to source locally, and I found this Li-Poly battery.
https://leeselectronic.com/en/product/8837-8837BATTERYRECHARGEABLELIPOLY37V.html

So I seem pretty set, but I have one question. The battery from the mouse has a 3 pins connector while the new one will have two. My plan was to solder off the original’s wires complete with the pins, but there’s a third white coming from the original battery.
What is this white wire, and would it be required to solder back onto the new battery? I just don’t know enough enough basics to know if I could ignore that wire or not.

The 3rd wire may be for a temperature sensing resistor in the battery pack that the charger uses to ensure it’s not overheating the battery…

Can’t say what will happen if you use a battery pack without this…

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Well that is super wise and makes sense.

A little more research based on that shows the same batter does exist with the sensor, so seems I just have to try ordering one or hunting for one locally. Measurement wise, the battery inside was smaller but one of these Lipo Polymer should fit inside the mouse, 36mm wide and the battery here is 34mm.

Thanks for the clear explanation. When/if I get this, I should be able to

Seems like it’s all worked out. I’m just trying to run the battery dry before putting it back together but it’s lasting for days now :sweat_smile:

Soldering wasn’t great, it’s hard doing smaller wires, but I just put it back together and will just use it regularly and try a few power cycles to make sure all is well. Battery was cool though, so looking good!


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You can squeeze the battery back to its original shape, but it won’t fix the damage caused from expansion.

Interesting, but it wasn’t holding a charge, so I think it was beyond saving.

Also last update, so far the mouse has been working well. I’m turning it off when not in use when possible, it seemed like it took forever to charge but it may be a cable issue, not sure. Regardless it all seems to be working well!