Replacing a single cell from the middle of a Lipo pack

[E-racer]

Wow... seeing how these packs are made almost makes me want to order 12X 4-6S packs packs and converting them each to parallel on the cell level... Then just run a string of 12 of those now 4-6p packs in series. Each block would only need one balance wire, you wouldn't need any parallel boards ect... does heating the cells up when soldering hurt them at all?

 

[hurricaniac]

Lipo surgery, as has been stated above, is a scary process. I have done it only on the end cells of a pack and it had me trembling in my boots the whole way.

But if you really need to do it, take a deep breath and use heavy dental tape (NOT A KNIFE) to separate the cell pouches from one another by pulling it gently and slowly down between the cells.

Remember, the most expensive new lipos are still way cheaper than the cheapest trip to an emergency room.

-Bruce

 

[docnjoj]

A ceramic knife has helped me with LifePo4 but I imagine it would work just as well on Lipo.
otherDoc

 

[El_Steak]

Just a note of caution, I fixed 3 more packs and on one of the cells I had trouble getting the solder to melt. I heated the cell a bit too much and it puffed. Just a slight puff, but still.

Just to follow up on this, I had decided to keep that pack. I took it out today to prep the bike (spring is here!) and the cell that had puffed slightly was completely dead now (0V). I replaced it again with another one, using 2 soldering iron at the same time to apply maximum heat for the shortest duration, seems to have worked fine this time.

The difficulty in this case is that the cell is at the end of the pack so the heat tends to be sucked in by the big 10AWG discharge wire soldered to the terminal.

BTW, thanks for the video Metallover, it's pretty much how I do it as well.

 

[Ypedal]

http://www.ypedal.com/Lipo/repair.htm

 

[jateureka]

Thanks for posting this. I'm off to try a repair on a LiFePo4 pouch cell battery that's dropped 2 of the 8 cells.

 

[zEEz]

ESteak, thanx for the tutorial and the nice images ...

It came just handy to me since I just bought a similar Turnigy 6s pack lemon and I'm
waiting for 2 more 3s packs to rebuild it ... hope they are not lemons those last packs too ...

have fun!

 

[dnmun]

Thanks for posting this. I'm off to try a repair on a LiFePo4 pouch cell battery that's dropped 2 of the 8 cells.

i find the most common problem with the pouch packs is that the tabs break off just where they exit the mylar of the pouch.

handling an older pack usually breaks more of the adjacent cell's tabs too so examine the tabs closely to see how many of them may be broken before disassembling the pack.

use the technique snowranger got started of cutting through the pcb subconnector with a dremel or diagonal grinder with a metal blade so that the bad cell can be removed without flexing the other tabs, then connect the new cells with a short piece of copper wire instead of trying to reuse the little pcb subconnectors.

i find that it is usually the top cell that goes first, tearing the tabs off the positive side of the top cell on the end.

 

[auraslip]

Has anyone found a safe way to open the hard case packs?

I'm not fond of the idea of shoving a razor blade in there....

 

[zEEz]

Has anyone found a safe way to open the hard case packs?

I'm not fond of the idea of shoving a razor blade in there....

In another thread, or maybe earlier in this, I read someone telling to simply insert
a flat screwdriver in between the 2 halves, starting from the shorter side and
pry it open ... expected to be quite simple ... :wink: 8)

alternatively, charge the pack with wrong polarity and be prepared to see it
splitting open automatically because of PUFFING

have fun!

 

[dnmun]

i have found that a guitar pick is the best tool for opening the plastic snap catches on the plastic parts on my laptop. that is how i got the screen surrounding off when i had to get to the inverter, and also to open the laptop case when the screws were out. not easy either.

 

[zEEz]

Hey guys and girlz!

I received two 3s Lipo packs type 40C 2200 Turnigy ... I decided to open and
split one of those new packs to repair a similar lemon pack that I bought 8)
the previous month: same Turnigy consisting of 6 cells, but having 3 damaged in various
way .... one puffed, and two low voltage ...

I must admit the tutorial here has served well ... I used a hard plastic card
to separate the cells, soldering iron to desolder, a bit of patience and some luck!
The resulting good 6s pack is almost cosmetically fine ... even the shrink tube
that I managed to reuse looks ok ... I'm cycling it just now .... 8)
If anybody is curious I can put few pics, but essentially I started with a 6s and a 3s pack ...
I took away 4 cells from the 6s and 3 from the 3s ... than I refitted the 4 best
cells in the 6s pack ... and I have now a few explosive spares to burn up ...

have fun!!