Craig, you have to decide if you are going to balance charge or not. If you are going to balance charge, the best charger out right now is the FMA CellPro 4S. If you are NOT going to balance charge, then you can use any nicad capable charger as long as you use a "Dapter." You can find a Dapter at SLK Electronics, or maybe even at the website in my signature. The dapter allows you to charge 1 A123 cell for every 2.5 nicad cells your charger will handle. The dapter can handle up to an 8amp charge, so the charge rate will depend on your charger's capabilities.

Having said all that, if you are still undecided on balance charging, or not; most information and research out shows these cells do NOT need to be balanced, like their Lipo cousins. Especially in 2S-6S configurations. While it certainly isn't going to hurt to balance them, you might as well save yourself an extra $5 per battery.

So Joe, are you charging through the switch or direct to the battery? I decided to do one A123 2300 two cell on my 35 % and will likely recharge after each flight until I get a track record going.

I wory about how many amps you can send through a switch....say smart fly type witout damaging it. Sure would be nice to not have to cut the canopy loose each flight.

RDB

I charge direct through the switch with the Cellpro--been doing it that way all summer with the JR switches.

Rich - if this is any help.... I have three airplanes, using Hitec 5955's on ail (2), elev (2) rudd (1) and a Hitec 5625 or something like it for throttle on all three. Average current per flight is about 265-340 ma, depending on throttle setting, how crazy, etc. These are average of 8-10 min. flights.

BTW - what I do is keep track of radio "on" time at the flying field per session....then watch the Cell Pro tell me how much current it has to put back, and I go all the way through peak, just to be consistent.

I use dual switches just to provide redundant paths; each is rated at 5A DC, I believe, they are the Maxx Products Heavy Duty charge switch.

Thanks guys, so I keep the amps down to say 3 or so?

I am only using the one Smart Fly fail safe switch to take the 18 g deans to the power expander in the 35%.

On my EF-88 I did my 2 cell A123 at 5 amps after a day of flying and put 699 mAh back in in 10 minutes flat.......before I could break down and put it in the trailer, done! That was after about 5 flights at 10 or more minutes each. Cool stuff.

It's surprising how little power a 50cc size plane actually uses. People have been massively overpowering them.

BTW I skipped over 8 pages of posts. Are we still talking about A123 on ignitions?

TF

If 2.5 ounces means the world to you - get a pair of VPXcells for ignition -1100ma (2.5 oz all ready to go ) .
on any single cyl -this is plenty for a day
on twins -depends on how many flights and rpm of engine !
Add diodes if you have 4.8 ONLY type ignitions - be sure to get large diodes .
many advanced type ignitions (with multiple functions uch as included tach,auto cutof etc., like a full sip of power for each cycle -
Do NOT starve the ignition module .
you could kill it.

What solider are you guys using to build your own packs, and are you using the tabs that are already on the packs?

REgular rosin-core electronics solder
Yes

I am on my way to pick up two packs of VPX to build two packs for my gas pattern. The total weight saving over two nicad packs is worthy every dollar!

Yep.
Sure is.

I have a Rcxcel red label with a ver 2 sticker on it I wired 1 5402 diode in series. Is this going to be acceptable 0ver the long term? Thanks Bob

Sounds like it should be fine. That's consistent with the Rc Ecxell instructions, so I can't see what problem there would be.

I looked up the 5402 diode, I don't think the voltage drop you get will be enough since it uses a metal semiconductor.

http://www.secomtel.com/UpFilesPDF/P...I/59682349.PDF

I would go with a 1N4001 Rectifier diode. They are rated at 1A and will drop the voltage ~0.7V because it is made of silicone.

http://www.onsemi.com/pub/Collateral/1n4001rev5dx.pdf

I ended up going with a PTC205 silicon Diode from RadioShack Catalog #: 276-1114 Contains 2.5A, 1000-PIV silicon diodes. I checked the voltage drop with my Fluke 87 meter and I am getting a 0.7 Vollt drop. My concern was that my a123s when fully charged put out 7 volts for the first couple of minutes with a input to the rcxcel ver 2 of 6.25 volts. I tested this with the ignition unit firing a plug installed at fequency of 181 Hz ( 10860rpm). Interesting note I was getting a output voltage to the hall sensor of 5.0 volts. Bob

Tried VPX 2cell pack as ignition battery on a ZDZ 40 engine with a ZDZ ig. module. No diode is needed.

The engine seems running smoother than a 4-cell Nicad pack.

Less weight also.

Like it.

Excellent! That's more great experience to add to the knowledge.... thanks!!!!!!

ANy thoughts why it seems to be smoother?

Do not know the exact reason. Maybe higher voltage produces stronger sparks? The same smoothness is there with a 5-cell Nicad pack. On the 4-cell pack, the engine runs fine but I can notice the rough spots at idle.

My Da 100 ran fine on a Vpx pack, I flew 6 flights but couldnt tell what I put back in as the Cellpro seemed to be acting up. Tried charging thru the switch and direct...I guess it must have as I got 6 flights.
Charged the 2 x 2300s just fine.
My Bantam charger, which will charge LiFe without balancing, charged up the ignition Vpx just fine so now Im confused....maybe the Cellpro doesnt like the ignition circuit on the Neg wire, signal wire is not connected, maybe it doesnt like Vpx cells I'm starting to think as the voltage rises so fast????.

Ive charged the VPX cells with my cellpro a few times and it didnt seem to act any different than it did with the 2300 cells..Ill have to try it again and pay closer attention.

Well the Bantam only put in 68mah, so whatever the Cellpro did it must have put some back in as i dont think I would have got 6 flights.
Hmmm
Will have to try it again, just need another 60 degree, windless blue day aint winter great!!!

My Cellpro also errored out fault code said voltage went to high. My pack was already almost fully charged. I am going to pull a couple hundred ma out and see if it errors again. If it still has problems I will use the Black and Decker charger. I modified the empty Battery case to use as an charge adapter for my pack. Bob

OK I ran some tests charging my 1100ma A123 2 cell pack if the battery is charged greater than 80% the charger will error out (error 13) due to battery voltage going to high in the final ballancing stage. The charger goes straight from fast charge to ballancing with no beep at 95%. Anyone know someone at FMA maybe they can make a downloadable patch to slow the final charging stage.

I was soldering a wire on a VPX pack when I noticed an orange flame shooting out of the other end of the battery. Since then I solder to the pigtail that is crimped on.

Tell us more about the orange flame!!!!!!!!!!! [sm=thumbs_up.gif][sm=thumbs_up.gif]
Is that some variation of "letting the smoke out" ??????