I was curious about what the insides of Milwaukee’s M12 battery packs look like, and it turns out it’s fairly simple:
There’s some things that aren’t visible from the schematic:
- The connector pinout is done CCW, just like an IC.
- R1 and R2 are 0603 resistors, so consider that when load balancing.
- I had trouble reading the numbers on R1 & R2, so while I think it read “01B”, it might have read something else.
- There’s no part number on the NTC resistor, but it’s 10kΩ at room temperature, roughly 8kΩ after rubbing it in my fingers, and 14kΩ after being cooled with acetone. I’d just go ahead and call anything under 2kΩ “overheated”.