I recently Retrofitted a couple of old Milwaukee 18V batteries with LiPO packs from the RC car world.
I wanted to share this because there are probably a lot of folks out there with Very high quality Expensive paperweights that might benefit from this.
I have the full Milwaukee 18V set which was a pretty high end set and have really nice build quality. Unfortunately they were only good for doorstops because the batteries died, and the replacements are about $100 each.
I decided to fit a Lipo battery pack inside, and use my RC car charging system to charge the batteries. at the time the pack that i ordered was $25 each.
Here is a picture of the battery shell, the new Lipo pack from HobbyKing, and what was inside the original pack:
After investigating the pack that was inside the original battery I believe that there is a balancing charger built into each battery. You CANNOT use your existing charger with this mod, you must be able to balance charge the LiPO battery pack. The cheap “charger” that sits on your workbench is basically just a 12V power supply, all the intelligence is built into the battery.
Getting the new pack to fit in required quite a bit of dremeling. Specifically one of the screw channels must be eliminated, and various other supports must be shaved down a bit.
I have stripped a few Milwaukee batteries down at work and shared the cells with others
Samsung 15m’s if I remember correctly.
if I was paying for them I would try to repair them.
but having seen how fragile they were I wont buy for my own use
Nice mod, simple and cheap but except from the cell checker no battery protection. Wouldn’t it be possible to connect the Li-po to the existing battery pcb to have deep discharge protection?
I got my hands on a free Dyson vac with toasted batteries. I might just buy a lipo pack and use it like you use your powertools. Difference is, the batteries on my Dyson have no pcb at all. There is no balance charging going on at all, just 4wires. 2 for +and- and 2 for temp check. The overload current- and deep discharge protection happens in the vac itself. But no balance charging which why I guess the batteries die so fast.
Thanks,
I am not an electronics engineer so I want to keep it simple that’s why I didn’t try to use the existing pcb inside the battery.
Also I read somewhere that Milwaukee put some kind of end of life counter in the pcb that just shuts everything down, so it might not be useable even with new batteries.
Another small issue is that the lipo pack had slightly higher voltage per cell so I am not sure how well the balance circuitry would work.
I am not going to use the tools on a heavy duty cycle anyway, so I am just happy to have use of them, and will be careful not to overdischarge. The alarm works nicely for that as well.
Good luck with your Dyson project.
