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Turnigy Acucell 8150 connection break?

I have 8400mAh batteries x2
these fellas:

and I first bought a 50W charger which maxes out at 3A and was timing out before it could charge one.
So I got a Turnigy Accucell 8150 so I could charge at 7A and hopefully charge them quicker. (Still less than 1C)

Just tried it on my battery B, after about a minute it alarmed with Connection Break.
(I’m using the LiFe balance charge option)
I double checked the balance lead was plugged in properly as well as the main leads, all seemed well.

So I tried battery A. Same thing again. Hmmm.
So I put charge current down to 6A, even though I am running off a 30A PSU with no other load and tried again.

It’s been running now for 20minutes, but for ages was showing zero amps, and now at 0.1A it has allegedly only fed 14mA in. I’ve watched the 4 cells and 3 of them were 0.4v or so higher (now 2 at 3.36, a 3.6 and a 3.52) than one so maybe it is nearly charged already and attempt two is normal balancing charge behaviour?
If so that’s good, but why the Connection Error on both originally.

I am worried about battery B however, as on the side where the Zippy logo is

battery B is definitely slightly puffy looking (peak hight about 2mm higher than the corners) and there is give on the side If I squeeze it slightly.

Battery A is square sided there (maybe 0.5mm higher at peak over corners) and feels solid.
Have I already knackered one battery?
I have a feeling I discharged one too low first time out but I didn’t have them marked then so no idea which!

They can sometimes be recovered by charging them as another battery type for a short while. This is enough to bring the terminal voltage up to a level where the charger will then charge them properly as LiFe batteries. However, the cheaper batteries do have a fairly high failure rate and “bad” ones do exhibit the signs you have indicated.

…all at your risk of course.

I recommend marking your batteries with the date of purchase and an identifying number. This has helped me on a number of occasions in the past.

I have them marked now, but date is a good idea.

It’s still running on the A battery. 66 minutes, 86mA fed in. Current voltage 13.88V. It says end voltage 14.4V. Should be charged by xmas?

Measuring the balance plug on the puffy one with a DVM I get:
Black 0V
Blue 3.48V
White 6.98V (3.50V diff)
Yellow 10.54V (3.56V diff)
Red 14.08V (3.54V diff)

They seem about right?

I’ve bought 3 x lifepo4 batteries - all supplied with their own chargers ( which look nothing special). I’ve never had any problems with them, and I don’t have to faff around measuring individual cell voltages etc, in fact I treat them as I used to treat my SLABS. I would forget about Lipo unless I wanted to fly model aircraft.

I only measured the individual cells to see if I could detect a failed cell.

My ‘good’ one finally claimed to be FULL on the charger, so I tried the puffy one on it to see what happened (He who dares Rodney, he who dares…) And after about a minute it also claimed to be FULL this time.
Voltage on the puffy one measures 14.43V and the non puffy one 13.83V.

Allegedly LifePo4 fully charged is 3.65V which makes 14.6V

Is the puffy one OK maybe? maybe it was puffier when I got it, I never looked.
Is the 13.8V one OK too? Why low?

One suggestion – do not charge these potentially failed cells inside the house. LiFePo4 batteries are much less likely to catch fire, but I’m sure they can still make a caustic mess. I’d charge them outside on a non-flammable surface.

Yeah I’m charging it on a glass worktop saver just in case.

Checked the manual for the 897 and that states supply voltage 13.8 ±15% with is over 15V which is reassuring at least. Might take it tomorrow and try it when I change bands after my first session and see what happens.