Well I did a stupid.

[Dan Robinson]

Somehow, I've manged to  charge a 7.4v lipo, whilst simultaneously discharging  a single cell of an 11.1v battery I didn't realise was connected to the charger at the same time.

I didn't think that was possible on a balance charger, but there you go.  Cell 3 is sitting at a little over 4v so I'm guessing it is screwed.

All I can think of is to brute force it at very low amps by using crocodile clips on NIMh battery mode until I get to 3v or so, then put it back toghether and do a lroper cycle with it.

The pack itself isn't puffed up too badly which is the one promising thing.

 

[gavinkempsell]

Bin it (safely of course).

It's only a battery.

 

[Dan Robinson]

Actually,  I've just got my posh multimeter out to double  check.... 2 cells at 8ish volts and one at 4v.

Yet the charger now reports 8, 8 and 0

Hmm.

 

[gavinkempsell]

Hmm.

View attachment 123070

 

[Dan Robinson]

If its being disposed of, it being done so in a totally irresponsible manner of shooting the crap out of it whilst sitting in a containment dish. ?

 

[gavinkempsell]

Got my vote... do you need a recount?

 

[EDcase]

Could be worth trying your salvage idea just to see if it works.  Then keep it as a backup

 

[Tackle]

I'd err on the side of caution, for the sake of a £10-£15 battery, is it worth the risk ? 

Might combust when in use in a rifle, wrecking the gat, or worse, when being charged at home, doing god knows what?

 

[Dan Robinson]

I didn't think it was possible to get a lipo cell to 8v.

I think my charger is just confused, because I have the 3 red wires out of the balance plug, and it is definitely 8, 8, 4 on the 3 cells.

Now it's more an investigation rather than a salvage mission.

 

[EDcase]

Yeah thats strange and worth investigating.  Could have ended badly...

 

[Sewdhull]

You charged a 3S lipo? And killed a cell you think?

What's the voltageof the pack, not measured on the balance connector. With a meter, not the charger.

 

[Dan Robinson]

I think what happened is that I charged a 7.4v battery, not realising there was an 11.1 still connected (it was flopped over the side of the counter).

So somehow my charger has jammed 8 volts worth of angry pixies into 2 cells, whilst leaving cell 3 alone (4v). 

I would have expected the charger to see these two cells were at the correct voltage though or at least move angry pixies from one battery to the other. 

 

[Rogerborg]

Does your charger have a storage charge setting?  You could plug the mullered ones in and see if it'll balance the cells down to 3.7V or so each.

In an ECPD.

While filming it for Science.

 

[Dan Robinson]

Nah, I've tried all sorts of modes with crocodile clips, leccy tape and a tin foil Sowester.  

The charger just yells in pain.  Which the silly fecker should have done before killing one of my newst batteries.

Still Saturday morning fun will be had zeroing in me SA80, and perhaps adjusting the hop on my newly repaired Speccy...  I have a 7.4v where a wire snapped too close to the cells to be repaired safely.

Between these two and my FLiR, it has not been a good month for be and batteries.

 Said FLiR battery is registering  0v which is very odd.

 

[Sewdhull]

I don't see how a lithium cell can be 8v. It may be that the charger balancing resistors or other bits are damaged and the voltages are being incorrectly reported.

What's the voltage of the whole pack?

 

[Dan Robinson]

8.1, 8.2, 4.08 across the balance plug. 8.17 on the Deans.

 

[Sewdhull]

I'm assuming you are using a meter to measure those.

I'm sure you can see the anomaly there.

The lithium's won't be 8v. There is chemistry than prevents it.

It's possible that the balance wires are screwed up because that looks like 4 + 4+ 0 and it's being measured cumulatively.

The balance wires, 4 of them for 3s will have, from 0v, 4 8 12v on each wire moving from 0v.

0v to wire 1, 4v

Wire 1 to wire 2 4v

Wire 2 to wire 3 4v

0v to wire 3 12v.

Apologises if I'm teaching you to suck eggs, but the numbers aren't right.

 

[Dan Robinson]

No need to apologise bud....  They're certainly weird, but I had the wires out of the balance plug, measuring across the negative in the Deans. 

I've got a better meter to try, but I'm wondering if two cells are somehow working in series?

Balance plug is mullered now anyway ?

Interesting maybe, but I just dropped it accidentally, and two reds touched, generating some entertaining sparks, and a toasty battery outer shell.  I wouldn't have expected that (black wire was still secure in the balance plug).

 

[Sewdhull]

The red wires have a voltage relative to each other.

View attachment 123130

The voltages you are measuring are cumulative.

Measure between each red. The 4v red is cell 1.

One of the red to red connections will be 0v

 

[Sewdhull]

Here's a better schematic

View attachment 123132