A123 not for all!

[RappyMan]

I just joined the A123 crowd today with a 2 cell 2300mah A123 pack from radicalrc.com in my 30% Edge 540. I was hoping to replace two 5 cell packs (1600 and 2700) for the RX & also try and use the A123 to power the electronic (CH) ignition for the 50cc. This didn't work! Range was great just replacing the 2 RX batts, but using a regulator and feeding the ignition gave me zero range.

- is there a way to eliminate the "noise" the RX is seeing from the ignition?
(I'm using Futaba 8ch PCM receiver - 72 mhz)

- The battery showed up at 7.4 volts.... this seems much higher than the 6.6V that I thought A123 were suppose to max out at. Can anyone let know if this is okay????


Thanks
Terry

[50%plane]

What regulator are you using on your ignition?

I have a similar setup, except I'm on 2.4.

[dmcquinn]

I have never seen my 2-cell A123 packs show more than 7.2 volts. if you discharge them for a few minutes, I bet they drop off pretty quickly to 7.2.

I'd just use a separate pack for the ignition. There's no practical way to isolate them otherwise.

[RappyMan]

I used the pack to power the plane for testing - probably around 10 minutes - and it dropped to 7.0 volts. Still a little high!

I'm using a 5 amp regulator that I used in a Raptor 50 for years. Not sure of the make, but I think it was MPI. It has a output of 5.1 or so volts

[Wojcigitty]

I thought 6.6V was nominal, not max?

[decoy26]

Max volts on a 2 cell pack is 7.2-7.4ish. Typical running voltage floats around 6.5-6.7. Weird that it would stay at 7.0 for so long. Mine fall into the "normal" range after a couple wiggles of the rudder and stay there for a long time! You should not need any type of reg on A123 batts. I use them on both planes and ignitions zero issues 100's of flights.

[decoy26]

Also one note, 7.2 volts is really not different that you would get from a freshly charged 6v NIMH or NICD battery. You should be good. Just make sure that CH iginition you are using is ok for 6V use. DA cleared their ignitions for A123 but CH just recently started, and mine say 6V OK scratched into the back of the case. Call CH they will let you know for sure.

[scalefreak]

If you're using a variable reg, set it for 4.8-5.1v on the ignition. CH's are very happy there, don't ask how I know

As far as noise, the only thing you can do is put a ferrite filter on the leads going in and out of the ignition and reg or maybe moving different parts around to new locations (away from the rx...I guess long leads can be an issue too, though), but if it's affecting your range, I wouldn't trust it. Figure out what is causing the loss of range and remove it from the equation. The best things to would be to switch your 72MHz rx out with a 2.4GHz rx

Good luck man! Hope you get it all sorted out.

[XJet]

I would strongly advise against using the receiver pack to also power the ignition -- it just adds another point of failure and provides a very nice path for noise to reach the receiver.

For the sake of a separate cheap 1400mAH NiMH pack it's just not worth it.

[drewbags]

I agree, I would be very circumspect of using the Rx battery for ignition on a 72meg or 35meg PCM/PPM setup, sure it works for 2.4G but it could give you problems on the other system.

[decoy26]

I agree not using the same battery for RX and ignition, however I do know folks doing it with out any issues and they are also flying 72mhz. I prefer a stand alone battery.

[mflander]

You can buy an iron corps 1200 mah batt for your ignition from fromeco.org for $15. Hard to justify not clicking order if it affecting your range.

[wildhare]

Are you sure you have genuine A123 cells? 7 volts after discharging is unusual.

I would test it by really discharging them hard for a minute or so, pull 3 or 4 amps out of them for a minute, then recheckk voltage. If they are still up around 7+ volts then I suspect you have cells that are not the real thing.

TF

[Scott Gerber]

Even if some guys are having good luck combining the RX and IGN to one battery, I feel it's more prudent to keep the engine stuff completely separate from the radio stuff. The weight of a 4 cell nicad or 2 cell A123 or what ever battery is no issue to the "POTENTIAL" for interference on any band radio. The perceived benefits is not worth the risk in my view. It's rather funny because some guys beat themselves to death to have a redundant this and redundant that on a little 50cc class plane but cut their nose off to save 2oz. of weight by combining the two systems....


Scott

[Reza]

terry,

7.4 volt is high. It was over charged. 7.2 is when its fully charged. It will drop to below 7 volt in one flight or less time. Do not use same battery to power your ignition, noise can come from regulator and ignition module, through your common battery to your receiver.

Hope this helps. I didn't get to read all the posts, if it is redundant answer, sorry.