So I bought this excellent little 18650-powered handwarmer a few weeks ago: http://human-creations.com/items/energyflux-4400mah-rechargeable-hand-warmer-external-battery-pack
…but the enclosed batteries are total crap and I want to throw some higher capacity + reliable cells in there which involves a little handy work. I unscrewed the device open and discovered 2x 2200mAh unprotected 18650 li-ion cells wired in parallel with some circuit board between them. It was enclosed within the heat-shrink pack so I’m assuming it’s a PCB…? I e-mailed the company and I’m still waiting for a response to know exactly.
Sorry this isn’t exactly flashlight-related but I thought since some of you geniuses are knowledgeable in the world of li-ion batteries, you might be able to shed some light as to what this board is and whether or not it’s needed if I upgrade the unprotected 18650s with 2 higher capacity PCB protected cells…
Thanks!
Additional info:
The hand warmer charges the parallel 18650s simultaneously via micro USB connection > controller > the pack. The batteries are not to be removed once installed and do not have their own independent voltage checker. The only thing between the batteries and the (+) and (-) leads is this unknown circuit board. The leads solder onto a simple control board which determines low-voltage cut-off, charge status, etc.
The serial number on the unknown board is: XSY-3939 if that helps?