Can I make a 3s lipo from a duff 6s?

[dani_r]

I have a Turnigy 5000mah 40C lipo that I got from Hobbyking ages ago. It arrived with a duff cell (cell 2) but because I didn't use it for ages it was already out of warranty before I took it out of the box!

I did a little bit of testing with a voltmeter and found that cell 2 was duff, I just put it to one side with the intention of doing something with it at some point. Well, today might be the day.

I have a requirement for a 3s lipo for my soon-to-be-built quadcopter, and thought I might have a crack at making one. I know they're cheap enough from HK, but it's there and I like to play (safely of course )

Can anyone tell me if it's possible to pull one apart to get the separate cells? Then make another one with the good ones?

Any help appreciated.

Cheers

[waveydavey]

Yep, you can.

[dani_r]

Yep, you can.

Oh. Splendid then! Is it just a case of de-soldering the fins?

[xygax]

well sort of. and reorganising the balance connector so that the -ve is one end then the two taps and the +ve the other end of the connector (assuming they are XH)

then heatshrink...

steve

DO NOT CUT BOTH POWER WIRES AT THE SAME TIME !!! you will damage your snips.!

[cjcj1949]

I'd get the good cells down to 3.7V before doing anything. The gaps on the pcb are very small and it is very easy to short them out. Not too much of a problem if its a brief short. A longer short with a blob of solder could be a different matter, although the solder might melt and act like a fuse. Not a job that any sensible person would attempt. It is easier to convert a 6S into a 5S and that has been done ok. Anyone who thinks its a sensible idea definitely shouldn't do it. A video for posterity is considered essential. And yes, I've got some duff 3S cells I'm thinking of taking apart. It is possible and it is safe, if you do it right.

[vtrnutter]

When I am soldering packs for some "surgery", I normally put some hot glue around the area that I am soldering. That way, I can't actually short anything out accidentally. Then I just peel it off afterwards and move on to the next part of the job.

[Nick B]

DO NOT CUT BOTH POWER WIRES AT THE SAME TIME !!! you will damage your snips.!

And possibly your pants!

[cjcj1949]

When I am soldering packs for some "surgery", I normally put some hot glue around the area that I am soldering. That way, I can't actually short anything out accidentally. Then I just peel it off afterwards and move on to the next part of the job.

That's brilliant. I'm obviously wrong. There are sensible people who take lipos apart.

[Swashbuckler]

if the cells are stuck together I use dental floss to part them so no bending of cells or damage to the cell cover occurs. Waxed is best!

[dani_r]

Cheers for the input guys! I'll let you know how I get on.

[kylelnsn]

Make sure you have spare underwear on hand! Just in case!

[dani_r]

Make sure you have spare underwear on hand! Just in case!

I don't like working around these things at the best of times. Never mind taking one apart!

[stu-evans]

Yes; I've done it on a couple of packs now...biggest problem I found was getting the temp up high enough to get a good solder joint on the tabs as the cell acts as a huge heatsink...but you don't want persistent heat on the cell for too long either or you risk damaging it.

If you can get that right it's an easy job though!

[dani_r]

I have one of those 100w soldering guns. Will that do the trick?

[cjcj1949]

Make sure the soldering iron tip has solder on it or you won't heat up the bit you are trying to melt.