A123 charging problem
 

It seems that my battery saga will never end. I HAD thought that I had found the solution with the new A123 packs and new Hyperion DUO. I ran them twice, and they have more punch than I can drive right now. My packs are A123 brand, 6.6V 4600 (2s2p). I run two of them in my Revo with a HV-4.5.

I was initially concerned that I couldnt use the A123 balancer since the plug didnt match up to my chargers balance ports, but an actual customer service email from A123 they said I didnt need to worry about it (maybe it helps that I sent it from work - they'd love to have our airplanes running A123's!).

So yesterday, we ran the trucks hard enough that we both came home with broken parts! Tonight I put the A123's on the charger, but with each set of batteries, the charger only detects 1 cell (3.3V) on one battery. Did I most likely damage a cell on each one?

Sounds a bit fishy - what does the multimeter say?

i added hyperion taps on mine, just spliced the wires onto the +ve and -ve bullets and soldered a conector directly onto the shortened orange wire. then it ends up nice and neat! cost around $2 each battery to do... ive got a pic in my hyper 8.5 build page.

I measured 3.18V on one pack, and 3.8 on the other.

TC, I saw you post on the adaptor. I'll have to do that. Hyperion taps are the same as Flightpower, right?

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.

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

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...)

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.

No, not quite- Hyperion same as Polyquest, E-Tec, Poly RC, True RC, Maxamps, Xcite and Impulse.

FlightPower same as ThunderPower Apex, MPX and someothers I've not heard of. If you'll ck ALL eRC site for bamance adapter, they list the common ones.

http://www.allerc.com/product_info.p...oducts_id=3160

What is the open-circuit voltage you should not pass with A123?
Typically, when I check the voltage of my packs after running the truck, what's the minimum I should see If I don't want to abuse my A123?

3.6v/cell peak at full charge, 3.3v/cell nominal, 2.2v/cell discharge (but should rebound back up somewhat).

After I've run my pack empty, what is the safe voltage is should bouce back to? Sorry if I ask is because I have no way to know at what voltage they go down to under load...
After my run of tonight, I waited 15 mins and measured 2.7V per cell with no load. Is this too low?

Not a single one of our LHS carry balance taps of any brand. So I put in an order last night for six of these http://www.maxamps.com/HYP-2S-Tap.htm and since I couldn't make up my mind, I also bought a couple of these http://www.maxamps.com/HYP-MULTI-GOLD.htm.
The first one will require that I modify every one of my packs, not something that I really look forward to, but I can do it. With the second part, I think I can just make a pair of charging adaptors. I couldnt find 2mm bullet adaptors at Maxamps, but for the balance wire, I could probably use any type of female/male connection system, correct?
Any thoughts?

Sorry maybe I've lost the plot - what are you trying to do?

Add a hyperion balance taps to a A123 pack? Are these the "orginal" A123 performance packs with just one tap point?

Yes, I am trying to make up a balancing set up to replace the "original" single tap, so that I can "rescue" my packs.

IIRC it is a 2mm Bullet in the middle...

I would make a custom deals harness - i.e. create a short deans extension lead male to female deans. The wire the hyperion tap into the deans extension - red to red, furthest from black to back deans and the middle back to the 2mm bullet.

I think I'd be inclined to get that pack back up now by hacking together a direct charge lead for the dodgy cell - i.e. 3mm bullet lead off the centre of the pack and a single wire to a male deans either on the red or black side depending on which cell is 0v. I'd then just use the NiMH mode at .2 amps to get the voltage up...

Or just do as Jeff said .2-.5 amps across the whole pack to the volatge up...

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?

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?

Can you not rig something just to charge the one pair of bad cells - That would save you over charging the one set.

I dont know - guess I can try. The Duo wont let me connect the balancer with such a low voltage reading. And it appears the max they will charge to is about 3.57 volts.

I have never assembled or taken any type of pack apart. So....not sure. guess I dont have much to loose.

also, the charger has protection which wont charge any damaged batteries, so perhaps this is the issue???

You'd don'y have to take it apart - Charge using the balance taps...

Tried that...no go.....unless there is some trick to make it charge only one cell.....

I think that is what the charger is seeing. It thinks its a single cell (3.3V). I have one on the charger right now on Nimh at 1.0A, with the balancer connected, but after 45 minutes, its still only at 3.5V.

perhpas try running it again??? just a suggestion. looks stuffed tho :(

Do you have a volt meter to check what the voltage of each cell is at the balance tap? If one cell is totally dead and not taking a charge any more your effort is futile.

Not that this will help much, but I did find something interesting with my hyperion 5i chargers. They will attempt to repair packs that go below 3v per cell.

I over discharged an orion 3200 pack, down to 5.5v. The charger fired up and trickled out a low amp charge until the voltage came up and then charged normally.

I have also put single cells on these chargers that were under 2volts, and the charger has charged them up too. Same low amp start, until the voltage gets up a bit. Low amp charging takes a long time, sometimes days...

I think it was trying to do this. After about an hour on the charger, it would stop charging and gave a reading of "end flat check" or something like that.