[meindnoch]

Did you look inside the old battery? It may well be just a bunch of 18650 cells with some electronics in a plastic case. Just desolder the old cells and solder on new ones.

I did the same for my wife's cordless vacuum, and it works better than new, because the new cells are about 2x the capacity of the originals.

[Epskampie]

This is only good advice if you're good at soldering and know details about cells like which ones have in-built protection.

Otherwise you're just creating a fire hazard.

[stavros]

Luckily, I do happen to know that stuff, so I used the existing board with brand new 18650 cells. Unfortunately, the board seemed to brick itself when it lost power, so the vacuum kept complaining the battery wasn't kosher.

[meindnoch]

>This is only good advice if you're good at soldering

I meant soldering onto the pre-welded tabs that come with the new cell (unless you have a spot welder). You don't need much soldering experience for that.

>and know details about cells like which ones have in-built protection.

It's highly unlikely that the individual cells would be protected ones. Manufacturers are not stupid to pay N times the cost of a management circuit.

[Bayart]

I don't think you'll ever find a battery pack using cells with integrated low-voltage protection, if that's what you're referring to. All that stuff is managed by the BMS. What you should be on the look-out for is the cell's operating range, continuous and max power. Personally I use buy VT6's in bulk and never think about any of that.

[miniwark]

Lets go with the usual reminder: de-soldering / soldering Li-ion cells can be super dangerous. With a bit too much of heat it can fire or even explode...

[meindnoch]

Hobbyists should buy cells with pre-welded tabs. You solder onto the tabs, not the cell terminals.

[cogman10]

It doesn't quite explode. Instead it shoots out a super hot flame that is nearly impossible to put out.

Imagine having a blowtouch that you can't extinguish or touch which is likely rolling around.

[ssl-3]

That sounds exactly like one of the kinds of deflagration (aka low-speed explosion) that seems worthwhile to discourage people from invoking.

"Hey, the worst case is that you get jets of super-hot flames that are impossible to extinguish!"

[stavros]

Don't solder lithium cells, even if it goes well you'll ruin them. You need a spot welder.

[stavros]

I did. Still, DRM.

[djmips]

DRM feels like conjecture. You admitted to working on it, it's also possible you broke it / didn't hook it up correctly?

[stavros]

Maybe, but I also know how to measure voltages, and everything was fine.

[ssl-3]

Except, I guess: It didn't work, so it wasn't fine.

[stavros]

I mean, if you want to think I broke it, you're free to. The fact remains that my battery connections were correct, the voltages were right, but the vacuum didn't work with either the battery I made or the new one I bought.