Well, I just couldn't fight my curiosity an longer. I've been reading just about everything I can find in the forums regarding this new(er) technology.

I purchased a DeWalt pack off eBay last week and ordered and CellPro charger from FMA-Direct. I assembled my first RX pack and hooked it up to the charger. Everything seemed to work fine and I hope to try it out in my Funtana X 100 this weekend. I do have a couple questions though.

I let the CellPro completely finish--until it said "A123 Charge Done" and the individual cell voltages were slightly off: 1 = 3.48V 2=3.51V. The overall pack voltage showed 6.99V. Is this normal? I really expected the individual cells to be closer after the CellPro worked them over.

The other thing that concerns me a little about these cells is that as a 2-cell pack, one bad cell would drop pack voltage below the cut-off for most, if not all receivers out there. I'm assuming that charging these packs on the CellPro I'll see warnings of poor cell performance way ahead of an actual in-flight failure. Is anyone else worried about this?

Thanks.

[quote=sgillmore;311458]
I let the CellPro completely finish--until it said "A123 Charge Done" and the individual cell voltages were slightly off: 1 = 3.48V 2=3.51V. The overall pack voltage showed 6.99V. Is this normal? I really expected the individual cells to be closer after the CellPro worked them over.
quote]

The two 2-cell packs and my 4-cell packs have never been off. 3.48 anc 3.51 is not very off though. That is only .03 volts. Do you know what the starting voltage was? Were those reading right after the charge or a few minutes later? They do settle a litle after a while. I wouldn't worry about a bad cell esp. since you will be drawing so little current from them. I think if you cycle it once, they will be the same.

What is the peak charging voltage for the Cellpro?

3.6 volts per cell. I will see it peak there but after the charge, the A123s seem to go to about 3.5 volts/cell after the charge finishes.

Much ado about nothing
first - the cells need some activity to be at their best -
that is: use em
If you can't fly em -- make a simple discharger from auto tail light bulbs (#1157) and run em down
two of these bulbs will take about 30 minutes
the lights will go out rather quickly when the pack is below 2 vs - remove load -and charge again - if you run the packs really flat -they will recharge but the Cell Pro will get all worried and slow charge for a while --cell pro is based on a LiPo charger design
so buy a VOLTMETER (any digital one $5-20)and measure voltage during discharge - you will see it hover around 6. 4 for a long time then at about 20 minutes the charge will start to drop - when it hits 3v - recharge and record amperage to fill
typically -- 2000ma

[quote=hybris;311540]

Originally Posted by sgillmore

The two 2-cell packs and my 4-cell packs have never been off. 3.48 anc 3.51 is not very off though. That is only .03 volts. Do you know what the starting voltage was? Were those reading right after the charge or a few minutes later? They do settle a litle after a while. I wouldn't worry about a bad cell esp. since you will be drawing so little current from them. I think if you cycle it once, they will be the same.

Of course I didn't think to record the starting voltage. The readings were definitely taken some time after the charge--maybe as much as an hour. I left them unattended in my basement shop while I was upstairs.

I'll try giving them a cycle and see what happens.

Thanks!

Originally Posted by dick hanson

Much ado about nothing
first - the cells need some activity to be at their best -
that is: use em
If you can't fly em -- make a simple discharger from auto tail light bulbs (#1157) and run em down
two of these bulbs will take about 30 minutes
the lights will go out rather quickly when the pack is below 2 vs - remove load -and charge again - if you run the packs really flat -they will recharge but the Cell Pro will get all worried and slow charge for a while --cell pro is based on a LiPo charger design
so buy a VOLTMETER (any digital one $5-20)and measure voltage during discharge - you will see it hover around 6. 4 for a long time then at about 20 minutes the charge will start to drop - when it hits 3v - recharge and record amperage to fill
typically -- 2000ma

I wasn't very concerned, just thought I'd ask. I have a nice voltmeter and a 2-bulb discharger left over from my R/C car days, however--I wonder if there's any reason I couldn't use my Duratrax ICE to discharge these packs. I know it doesn't support A123 chemistry, but will that matter on a discharge? I can configure it for 2-cell, 3.0v/per cell cut-off with a 4A discharge rate. Once it's done, hook it up to the CellPro for a proper balance charge. Do you see any reason that wouldn't be OK?

Also Dick, I've read a LOT of your comments here and on RCU (thanks for all the guidance BTW) and I respect your opinion. I'd be interested in any comments you might have regarding my second question. I remember you mentioning in a post that every time you charge the packs with a CellPro it's like a health check. Is that why you aren't concerned about an in flight cell failure? I'd say a lot/most of us have experienced a bad cell in a NiCD/NiMH pack at one point or another, which is why I've always leaned towards 5-cell packs.

Thanks in advance.

I dont want to speak for Dick but the Cellpro will show the individual voltage of each cell as it is charging so if you do have a bad cell you should be able to see it--this may be what he was referring to

A discharger should be fine - the 123 cells -so far -have shown to be the most bulletproof cell of any type -I have used . the CellPro lets you see the voltage on each cell as the charge is on going . that is good info to have .
until th cells get a fe working cycles -the top off voltages may be a bit low or different
I spent part of an afternoon trying to top off packs - what a waste of time - When I finally figured out that all they needed was a few good full cycles -I was digusted with myself for pussy footing around and trying to treat em like NiMh shelf voltage V drop issues or fragile LiPos - - they worked just fine - just USE em.
charge em -a week ahead of time if you like - then check em when you go to fly - so far - mine all stay close to final charge readings-a week or two later.

There were earlier comments regarding disassembling the DeWalt batteries. I went to a local supplier and purchased a #10 drilled torx tip for my battery powered screw driver. The top was off the battery in seconds. The lesson learned from trying without the drilled torx is that the screws holding the batteries in place are non-removable screws that contain a small ball in the center to prevent a normal #10 torx from working. FYI

they are the "tamper proof type"

I've bee watching this thread for a while now, and have a Dewalt pack that should arrive in a day or so. I have a Triton charger that works well for all my other battery needs. What should I get for the A 123 batteries? I will only be using them in a 2 cell pack for RX and ignition batteries.
thanks,
Z

FMA have a charger but I will be posting here tonight ot tommorrow another option I just had arrive in the big brown box.

I finally got try my A123 RX pack. One trip the field (5 flights) and I'm already SOLD. I don't technically have any giants, but I test flew my first pack in a Funtana X 100. It's equipped with a Saito 1.25, AR7000 and a mix of Hitec digital (tail group) and analog servos (ailerons & throttle). Two ten minute flights barely phases the battery. I'll have to track some exact numbers the next time out, but I have no doubt I could comfortably log six 10-minute flights before recharging. And as many have said before me, it recharges so quickly, why not top it off every couple flights.

zx32tt: Due to the many recommendations from A123 and Li-Poly users, I purchased the CellPro Balancing Charger from FMA Direct. I've been using it on my A123 pack and my Li-Polys. All I can say is I wish I would have bought one of these chargers a long time ago. I highly recommend it.

http://www.fmadirect.com/detail.htm?...218&section=45

The Cellpro is great, I just wish it had more buttons. It is a pain to switch from A123 to Lipo 1C.