Battery question - LiFePO4s

[ActionNeil]

Hi,
I have some LiFePO4 batteries (3S, 9.9V) that I charge with an Imax B6AC charger. This has worked just fine up to now, but one of my batteries has started acting a bit funny when I try to charge it.
Normally the charge goes in at 1A right up until the cutoff voltage (10.8V) is reached. That doesn't happen with the one battery I'm talking about though - that one reaches a peak of about 10.6V when I first plug it in, then drops off to about 10.3V and stays there in a kind of cycle. It pushes 0.1A through, and the voltage quickly raises a bit. Then it kills the amps and the voltage goes right back down to 10.3. it keeps doing that for as long as I've left it.
I've run this battery harder than my others, and sometimes I must have come close to the discharge limit, but I always stop and disconnect it immediately when I notice any drop in rate of fire, and stick it on to charge ASAP. It's a bit softer and puffier than the rest, but you wouldn't notice unless you knew to look for it.
Am I buggering up my battery, or is this normal?
Cheers :D

[Siggi]

Re: Battery question - LiFePO4s

I'd say all those symptoms, considered in the round, indicate it's shagged.

[colinjallen]

Re: Battery question - LiFePO4s

Agreed; poor charging characteristic, soft and puffy = a very sick battery.

[ActionNeil]

Re: Battery question - LiFePO4s

Damn
What sort of practices should I follow to prevent it happening to any of my other batteries?

[Siggi]

Re: Battery question - LiFePO4s

How old was the shagged one? How many times had it been recharged? It might have been a lemon or a crap brand. Short of refraining from hacking a hole in one or badly denting/crushing it or madly over-fast-charging it there's not much you can do to cosset them. You're not supposed to leave them fully charged for longer than a few hours, days at the most, but that seems to be bollocks. Maybe it shortens their life but the inconvenience of pampering the sods is easily overcome by buying new ones a little more frequently (once every 30 months instead of 36).

[ActionNeil]

Re: Battery question - LiFePO4s

It's about a year old now. I can't have cycled it more than a dozen times.
I had another look at it this morning, and it seemed to be very nearly as firm as my other batteries again. I put it back on to charge, and it hit the cutoff voltage after about 5 minutes, and balanced correctly.
Yesterday I was testing out some gearbox work I'd done and I absolutely ragged it. It went straight to charge after that. I'd guess it kind of recovered overnight, in the same way you get a rise in voltage if you stop draining a battery for a while.
Cheers fellas!