Transforming a 'Dead' 3s Lipo into a viable 2s Lipo - Don't Discard it! - Step by step fix it video

[Phil Green]

3 hours ago, Jason Channing said:

Inside the pack the cells are still wired in series whether or not you disconnect the balance lead. Probably the daftest thing Ive read in a long time and the most dangerous.

I think you've completely misunderstood Jason. Assuming cell 3 was the faulty one, the disconnected balance lead (one wire) is from the positive of the removed cell 3, and hence this wire is redundant.
The positive power lead which is floating after removing cell3, is moved to the pos of cell2.  Its very simple, not at all dangerous if done by someone competent, and not 'daft', in fact personally I think its daft binning of perfectly good Lithium  🙂

 

Edit: I just watched it again and realised that its cell 1 that has gone, so the balance plug does need to be changed after all, sorry Bonzo thats me speed-watching.  If cell 3 has gone then 3 wires of the 4S balance plug can stay, the last wire is redundant and can be snipped or insulated away.

In Bonzo's case its cell 1 so its easier to replace the whole balance lead than to shuffle them all up one - its only 3 wires so not worth messing about 🙂

In order of ease of fixing, a bad cell 3 is the easiest. A bad cell 1 is a little bit more faff, a bad cell 2 is double the effort, more so if its a PCB for inter-cell links - I probably wouldnt bother.

Edited February 15 by Phil Green

[Bonzo Moon]

43 minutes ago, Phil Green said:

The balance ports are simply commoned so the charger sees a 2S 👍

Yes, I see that would work. Wasn't sure how the balance plug socket was wired. 

[Phil Green]

thats assuming cell 3 has gone Bonzo, wont work if you removed cell 1  🙂

Its because after removing cell 1, the 3S plug starts with the redundant balance wire, which would have been the negative that everything is kelvin-referenced to.

You'd have to shuffle them all up one pin, which is a lot of faff, easier to add a 2S balance lead as you did 🙂

Edited February 15 by Phil Green

[Bonzo Moon]

33 minutes ago, Phil Green said:

I think you've completely misunderstood Jason. Assuming cell 3 was the faulty one, the disconnected balance lead (one wire) is from the positive of the removed cell 3, and hence this wire is redundant.
The positive power lead which is floating after removing cell3, is moved to the pos of cell2.  Its very simple, not at all dangerous if done by someone competent, and not 'daft', in fact personally I think its daft binning of perfectly good Lithium  🙂

 

Edit: I just watched it again and realised that its cell 1 that has gone, so the balance plug does need to be changed after all, sorry Bonzo thats me speed-watching.  If cell 3 has gone then 3 wires of the 4S balance plug can stay, the last wire is redundant and can be snipped or insulated away.

In Bonzo's case its cell 1 so its easier to replace the whole balance lead than to shuffle them all up one - its only 3 wires so not worth messing about 🙂

In order of ease of fixing, a bad cell 3 is the easiest. A bad cell 1 is a little bit more faff, a bad cell 2 is double the effort, more so if its a PCB for inter-cell links - I probably wouldnt bother.

I'm very guilty of speed watching, scrolling through, we all do it!  I actually said in the video that had it been the centre cell of the 3 it would have been more of a pain of a job! Luckily as it was the end one it was easy to peel it off, re-solder the neg wire and put an old scrap 2s balance plug on.  If balance socket leads are commoned to each socket I'll try using the 3 plug next time. 

[Phil Green]

Balance connectors are wired in parallel.

Inside the battery, balance neg and power neg both go to cell 1 neg

and the last balance wire goes to the last cell pos and power pos

If it would physically fit, you could plug your 2S at the bottom end of any socket 2S to 6S 🙂

 

 

 

Edited February 15 by Phil Green

[Bonzo Moon]

3 minutes ago, Phil Green said:

Balance connectors are wired in parallel.

Inside the battery, balance neg and power neg both go to cell 1 neg

and the last balance wire goes to the last cell pos and power pos

 

 

 

I know the way  they are wired in a lipo thanks,   I have built and repaired a good few lipos.  I just didn't know how the ports were wired in my charger. 

[Phil Green]

4 minutes ago, Bonzo Moon said:

I know the way  they are wired in a lipo thanks

I know you know, but its apparent that some of your viewers dont 🙂

[Bonzo Moon]

19 minutes ago, Phil Green said:

I know you know, but its apparent that some of your viewers dont 🙂

Fair comment!  I was a bit surprised just how much discussion the post has created.  I did include a very small diagram in the video of cells in series and tried to explain where the balance lead is connected, but as you say, some confused comments.  

 

Just wanted to show folk that one dead cell doesn't necessarily mean you need to throw away a lipo.  😉

[PatMc]

5 hours ago, Jim Hearnden 1 said:

Danger UXB that are old enough to remember it!  

https://en.wikipedia.org/wiki/Danger_UXB

The series was running on Freesat ch 82 - TalkingPicturesTV.co.uk  I think tonight's was the last episode but it's all available on their catch up system.

[Phil Green]

Trigger Point is a current equivalent, I enjoyed it, they're repeating series 1 right now

https://en.wikipedia.org/wiki/Trigger_Point_(TV_series)