[Sabrejock]

The ESC that came with a new foamy fanjet is labeled KMS 30Amps. And in smaller print "2-3LiPO". Do you think a 4 cell 1100 A123 be too much s far as voltage is concerned? Tex.

[Ken Currell]

Using nominal voltage of 3.7 for Lipo and 3.3 for A123 pack, it is 2.1 volts more than recommended.

Using fully charged votage it is still 2 volts higher than recommended.

I am not an electronics expert but IMHO.

It will likely work but the voltage regulator could overheat and shut down or possibly fail.

[Sabrejock]

Ta for that, Ken. I don't know a lot about these dinky planes. I did a bench run with a four cell pack and the smoke stayed put. It sure had a good blow, too. But I think I'll make up a three cell pack and see if it'll fly on that. I'd feel better knowing it's safe, even though the investment here is pretty small.

On second thought, if it's only the BEC that could fail, perhaps I could stick in a separate BEC like the E-flite. It weighs next to nothing. Tex.

[Ken Currell]

Fly it for a short flight.
Check the BEC to see if it is HOT.

If it is only slightly warm then try a longer flight.
I think that the way you fly will also be a factor.

HOWEVER. As I stated I am NOT ON EXPERT in this field.

Someone with a bit more knowledge about it might have a different opinion.

Cheers

Ken

[moo]

A primary concern should be the cut-off voltage, most speed controls are set to something like 2.9 volts/cell and the speed control needs to be programmed (or auto detect) the number of cells. How would this speed control know to set the cut-off voltage to 2.0 Volts x 4 cells?

[Sabrejock]

Originally Posted by moo

How would this speed control know to set the cut-off voltage to 2.0 Volts x 4 cells?

As my usual stuff has many A123's and I don't use LVC, I'll only guess that as this controller is a 2-3 cell it can figger the high voltage as a 3 pack, even though the start voltage is a bit higher than that of a three cell LiPO. We'll see.

Thanks, Tex.

[Flypaper]

I use a 4 cell A123 on a heli with the Castle Creations BEC with no problems. I also use a timer so I don't get to low voltage cutoff which is programmed into the BEC at 2 volts per cell for the A123s. Not nice to have it cut out on a heli. The ESC gives out beeps for the # of cells it recognizes. As Tony the Tiger says "works grrrrreat". Just as an added note, they run much, much cooler than the lipo, or li-ions. Barely warm, where the others come out hot.

[robonline]

Why not just get an ESC that will do the job you are asking it to do? That would remove the uncertainty and be a safer model. I think it's better to ask this question now rather than at the post mortem after the crash, especially if someone got hurt.
I know the ESC came with the plane but then again it probably recommends Lipos and you've changed that. I would use Lipos with this ESC or A123 with a new ESC, just to be sure.
Rob.

[DW_Crash]

Anybody have any idea when vendors will have ESCs that work directly with 123 cells? So we don't have to jury rig.

DW_crash

[Guest]

Originally Posted by Sabrejock

The ESC that came with a new foamy fanjet is labeled KMS 30Amps. And in smaller print "2-3LiPO". Do you think a 4 cell 1100 A123 be too much s far as voltage is concerned? Tex.

Which jet is it? Frankly, many of them have underspec ESCs to begin with, and simply switching from the stock 15 or 18c battery to a 25c one is enough to cook it. If it is 25 or 30a, it's probably on the edge to begin with, and keep in mind that many of these cheap ESCs are overrated to begin with. Most work fine, if kept between limits, but adding 2v is asking for it, in most cases. Adding a four lipo cell is a sure fire way to surely fire it.
It's not a question of the voltage regulator burning out, you can cook the actual mosfets on the board. Been dere, done dat.
Best bet is to switch up to a 40 or 50a ESC, and then you have nothing to worry about. But you are certainly playing with fire. Remember, too, the fan will unload in the air.
I have cooked a 30a 3 cell esc in a half second by accidentally putting in a 4s battery.