A123 charging problem - RC-Monster Forums

jhautz · 07.22.2008, 12:20 AM

Did you run them totally dead. Even though a123 are resistant to abuse you still cant just run them totally dead until the truck just stops. They have a minimum voltage of 2v/cell and running them down below that is not healthy for them.

Fortunately you can probably save them because they are such resilient cells. Set your charger to NiMH and a very low current setting like 0.5 amps and hook the pack to the charger for just a few minutes so you can raise them above 4v. then stop the charge and set the charger to a proper a123 charge cycle, but if you can set the current very low (like 0.5v again) and charge them like that. You should be able to get them back up to full voltage but it will take a few hours to get them there.

Be careful when doing this initial bump charge with the NiMH setting and don't forget and leave them on there. It shouldn't take much at all to bump them back over the 4v minimum so your charger will recognize them properly.

Once you start feeling the power drop off noticeably stop running them. Discharging them to that low repeatedly will certainly effect the life of the cells.

jhautz · 07.22.2008, 12:28 AM

Oh yea... and if you can balance them while you charge them it would be a good idea, at least during this recovery charge.

tc3_racer_001 · 07.22.2008, 06:42 AM

flight power im not sure... im pretty sure they are different. there are many tables on which taps fit which (i thin kthere is one on www.b-p-p.com somewhere...)

JThiessen · 07.22.2008, 08:49 AM

Thank's jhautz. I did in fact run them down pretty low - it seems that they have a relatively short drop off. I'm learning here.....but it seems that I may in fact be an old dog.

JThiessen · 02:28 PM

Quote:

Originally Posted by jhautz

Set your charger to NiMH and a very low current setting like 0.5 amps and hook the pack to the charger for just a few minutes so you can raise them above 4v. then stop the charge and set the charger to a proper a123 charge cycle, but if you can set the current very low (like 0.5v again) and charge them like that. You should be able to get them back up to full voltage but it will take a few hours to get them there.

Be careful when doing this initial bump charge with the NiMH setting and don't forget and leave them on there. It shouldn't take much at all to bump them back over the 4v minimum so your charger will recognize them properly.

Once you start feeling the power drop off noticeably stop running them. Discharging them to that low repeatedly will certainly effect the life of the cells.

Ok, I got all my packs rewired with Hyp. balance taps, and put one of the bad ones on the charger on Nimh setting, 0.5 Amp, but had to put it on 4.8V (it wouldnt let me set it to 6.6V). It started at 3.18V, and after two plus hours, it got up to 3.43V, but I had to shut it off (bed time!) - now this morning, I've had it back on for 1.5 hours, and they are only back up to 3.3X volts so far. It seems to be taking much longer than was stated above. I do have the balancer plugged in, but that also put some quirks in the process. The first time it scrolled through asking how many cells. I waited until it said 2 and pressed enter. It charged for a bit, then gave me a "low output voltage" error. So I re-did the connection, set it to 4S, and it seemed to like that setting. Does this sound right? I just wanted to bounce this off those of you who have done this, to make sure its going correctly.

I'm also curious, why set it to Nimh for the intial bump instead of A123?

JThiessen · 07.28.2008, 07:55 PM

I managed to get one of them to 4 volts. I then disconnected it, changed to A123 6.6 4600 mode, then connected the battery mains, then the balancer. It gave me an "Output Battery COnnect Error", and I then tried it without the balancer and recieved the same message. I then stuck a "good" pack on, and it works fine. So I wonder if I need to go higher than 4 volts?