Igor,

I assume that each motor set up was running at the 9000 rpm, could you post your ESC setting and how long each ran and the mah required. I am working with the A123's and am just about ready to get the test ship in the air so any information would be of interest, I have the AXI2820/8 motor with a 3s2p A123 pack.

Best,     Dennis

Dennis,
What is the capacity of your A123 battery? When I was flying my E-Nobler on a 3s4200 mAHr Lipo battery (average V~11V delivered to ESC), I was using about 2300mAHr. Is this total capacity consistent with your capacity? Prop was an 11-5.5.

I would argue to start off flying for ~3 minutes just to see how much power you pull out of the battery (you see that when you charge it back up). One thing I found was very useful for my flying was a "Talking Timer". It counts off the time for you so there is no surprise when the timer times out. Really pretty useful and costs ~$20. It is advertised in Model Aviation. It is worth the cost.

Alan

Dennis,
With the kV of your motor (1500), I think the A123's will be able to keep the rpms ok. But like I say, it probably is best to creep up on the final flight times, just to see how things are behaving. I do the same with a glow setup, when I am trying to find if I put enough fuel in the tank.

Hi Dennis,

I am trying to get up to speed on these A123 batteries.  After Brodak last year, I put all modeling aside.  These batteries seem like something to get excited about.

When you have time could you give us the physical dimension of yous 3s2p 4600 pack. Weight, and overall size would be of interest to me.

My Bearcat was using a 4000ma that weighed in at 14 oz.
Thank you

linheart

 

Thanks Mike,

After reading your response, I did some research on EBAY.  All the information I was interested in was there.  Based on your info and what I found on EBAY,  I will not be able to put together a package light enough to power the Bearcat.

Maybe next year some more technology will come along to enable me to get that quick recharge, no fire hazard, 500 recharges, 4000ma, 400 gram low cost, battery.

All,

Have now flown the A123 set up with the AXI 2820/8 and an APC E 11 1/2 x 4 1/2 prop also an 11 3/4 x 4 1/2 , both work great with the 3s2p A123 pack from Mec. This was in my test ship which has 625 sq, 57 oz. Lap times were 5.25sec on 63.4 ft lines. Flight time was 6 min and the governor was set for 8800 rpm which it held for both props through the flight. I am going to increase the pitch to 4 3/4 to bring the lap time to 5.0. I am now going to move to the next step which will be the modified Tutor II . This package seems to pull like a good 46. Battery draw down on the 11 1/2 prop was 77% ending voltage was 9.78 (3.26 volts per cell) on the 11 3/4 draw down was 83.4% and ending voltage was 9.69 (3.23 volts per cell). Motor was luke warmer (my guess is 115F ish)  but not hot to the touch, battery was just barely warm.

At $110 per made up pack from Mec with the ability to charge 1000 cycles, 30 min recharge (could go faster with the right charger, mine is a TP 610C and is limited to 10 amps, I have it set a 8 for now) and no risk of spontaneous fires (I know that with proper care on charging this has been controlled but it is still a risk with the Poly's, but the A123's are now being used by Dewalt and Black and Decker in cordless construction tools), this is the setup that makes sense even if there is a few oz more weight (total wt motor, ESP, Timer, A123; 4.5+.5+19 = 24oz). A purpose built 590 sq  ship with a film cover should be able to come in at 25oz for a total weight of 49 oz so this should work great.

Best,          Dennis