Faulty LiPo - What now?

[Bad Raven]

A while ago now I was supplied a near £60 GNB high discharge 4000mAh 6S with a dead cell.  VERY unusual, only ever had one other, a 1500mAh 4S. Not shorted, so 0v across pack output, fully unusable as was.

It had leaked internally into the transparent covering, making it unusually very visibly failed.

No real issue, it was refunded promptly on a photo and balance meter photo.  Unfortunately that was the end of current stock, so no replacement available to be purchased.

I "parked" the failed pack, isolated solo in a metal box in a shed for many months.

Finally months later new stock appeared and I bought a replacement.

With weather conditions finally suitable, and more months on, I got out the old pack yesterday, and no signs of anything worsening, other cells all holding storage voltage as supplied, no marking, no swelling.

So, working outdoors away from anything, I very carefully dismantled the pack.

The failed cell left me with a two cell pack and a three cell pack.

Unfortunately to be any use to me, I needed a 1S (for a remote longer duration feed for my Transporter2 Goggles as they only do 50mins or so on the internal) and a 4S ( correct for several of my planes, a couple of ex-NIMH drills, Whoopstor charger feed when away from mains, etc!!      

Oh well, in for a penny........    ......  In case you are wondering, splitting the packs after severing the pack to pack connections, was done by inserting a thin flexible 50mm wide steel from a filler spreader £1 shop pack I normally use for 3D print bed removal. This puts the cell covering at no risk of puncture, simply severing the double sided tape in several across cell passes. NEVER pull cells apart, its a big no no!

I already had correct fire resistant foam, tape, and large enough shrink wrap for both sizes.

So I split the 2S and soldered up a 4S, adding a 4S balance adapter saved as I always cut off the old ones before salt water bath when disposing of packs.

Currently they are both fully charged now and back in isolation for a month, then will be carefully introduced to service. 

I'm NOT recommending you try, but if you are a good fast clean solderer, have the right tools, and have the required electrical knowledge, you might be tempted..........but be aware, it is not a five minute job, so pack price and availability controls the cost effectiveness in doing it even if you do have the skills and tools.

YOUR call and YOUR risk.