Doing a search on batteries I came accross this site for LiFe cells that look to be similar if not the same as A123 cells but with what looks like easy to connect end posts. This might be worth checking out. If someone has already started to use them please post details.


http://www.lifebatt.com/LiFeBATT%20Web_4.html

Best,    Dennis

Igor,

You seem to have developed a package that works with the A123 cells. Could you provide some basic parameters for using them. I like the A123's because they appear to be less critical on the charging to be safe, would allow a pack to be installed in a ship and charged in place between flights which would allow for less handling (and opportunities for problems) could allow better cooling design (baffling of airflow) if you don't have to always remove them.

I have a project that I would like to use them on that being a Tutor II ARF, I think the power package would be something like: AXI 2826-10, 11.5x5.5 prop, Castle Creation 45amp ESC, Timer .

How close is this? I would like to have a flight time of 6min, lap time on 62 - 65Ft C to C lines of 5.2sec., ship is 30oz covered without power package, 594sq in. I know the A123 has lower voltage so if a different motor or ESC rating is needed please make a suggestion.

What configuration A123 battery pack do I need to build? What charger works with the A123's for fast field charge and slow shop charging. Since I am new to electric what other support equipment should I get to properly maintain these cells.

Thanks,           Dennis

I have a project that I would like to use them on that being a Tutor II ARF, I think the power package would be something like: AXI 2826-10, 11.5x5.5 prop, Castle Creation 45amp ESC, Timer .

How close is this? I would like to have a flight time of 6min, lap time on 62 - 65Ft C to C lines of 5.2sec., ship is 30oz covered without power package, 594sq in. I know the A123 has lower voltage so if a different motor or ESC rating is needed please make a suggestion.

What configuration A123 battery pack do I need to build? What charger works with the A123's for fast field charge and slow shop charging. Since I am new to electric what other support equipment should I get to properly maintain these cells.

6 cels will be enough for 5:15 to 5:30 minutes on APC E 11x5.5. It is enough for whole pattern without run on ground. I had it in serie and AXI 2826-10. It is relatively high voltage and so it runs at not so good efficiency. I think ~78% or so. I would rather try AXI 2826-12 which will be probably beter for those 6 cels. May be it will be enough also for APC 12x6. But I did not test it yet.

But I think it is all too heavy for such model and I do not think CC will survive with 6 cells. It will need another ESC (Jeti, MGM). If you want 4 cell battery you will need motor with say 1000-1100 rpm/v, but I do not think the capacity will be enough for 6 minutes of 11.5x5.5 prop. It will need smaller prop.

A123 is still worce (heavier) choice and I think it is usefull only on larger models.

Hi Gang,
Igor, I'm quite fond of the balancePro myself, and I thought it goes to 10 amps. Okay, charging the 2P 4200 mAH in under 1/2 hour sounds good to me. The Phoenix does fine with 5S LiPos, so 6S A123s cells shouldn't be an issue.

I would still look to a 3S 2P setup. The motor Kv would then be in the high 1300s to low 1400s for a 12-6 prop. Even an 8-turn 28-26 AXI would need a bigger prop like a 13-7. Hopefully we can find a 1400 kv motor with under 20 milli-Ohms resistance for less than maybe 180 grams weight. That will work nicely.

I'll go look.
Dean

You read my mind, Igor ...
It's all large print and pictures in there.

later Friends,
Dean

Dean, you still think of 12" or bigger prop with that axi motor? I affraid the capacity is not enough for 5.something flight time.

My setup 6s1p with axi 2826/10 works at relatively low efficiency ~75% and the flight time with APCE 12x6 was under 5 minutes (if I remember well 4:45).

If you can have efficiency over 80% with better matched motor, the flight time can be say 5% longer, but it is still too little.

But if your test will be succesfull, I think I will invest Axi 2826/12 for 6s1p battery and APCE 12x6 :-)  ... It will also run at ~80% efficiency

Hi Gang,
So what you have is a battery that forces you into a 3S-2P, 9.6 V, 4400 mA-H battery OR into a 6S-1P, 19.2V, 2200 mA-H battery.
What we have been running otherwise is a 4S 4200 LiPO at 14.4V with an AXI 2826/10 with a Kv of 920. All harmonizes decently with this combo and a 12-6 prop at 9000 RPM give or take a few hundred.

Igor's 6S setup was inefficient, as he says, because he needed a motore with a Kv of closer to 690, not 920. 920 X (14.4V/19.2V)= 690.
Then it would have been happy with a 12" prop.

Conversely, a 3S A123 will need a Kv of around 1440 to run the 12-6 at exactly the same R's. 920 X (14.4/9.6)=1442. Well, the 2820/8 has a Kv close by at 1500. There is a Neu motor thaat would be better, and close to twice as pricey, but that's another matter.

Assuming there is no big mismatch of battery voltage, Kv, then the total energy available in the battery and the all-up weight dictates the maximum prop diameter. As Igor said, the AXI 2826/10 was not a good match to the 6S A123. You'd need a 2826/14 or 15.

later,
Dean

Dennis,
All the 2820 motors can handle similar amounts of power, because the heat is dissipated through the surface area of the motor. For any power level, the heat you produce due to the winding resistance is identical for all winds (assuming all have the same amount of copper).
I fly a Scorpion 3020-12 which I think is nominally the equivalent of this AXI in my E-Nobler. I currently turn 11-5.5, although I plan to go up (one way or the other) in prop load next spring.
However this AXI is a 1500 kV motor, whereas my Scorpion is a kV=1100 motor. If you want to turn a bigger prop, you are going to want to drop down somewhere between a 3s or a 2s (lipo equivalent) battery, so that the ESC isn't handling all the voltage drop by itself. If you are really gung-ho on these LiFE cells, then maybe you can stack them in parallel, not series, to get the voltage down to the 8-10V range, but capacity of the entire pack up into the 3500-4000 range. Remember the energy you carry is independent of how you wire up the battery, and only depends on the number of cells and their individual capacity.

Dennis,
If you look at my E-Nobler thread, you can see that I started out with two 3s2100MAHr packs hooked up in parallel. If you look at my plots, you can see how much current I was drawing at peak from the battery. Off the top of my head this was less than 35A when I finally got the rpm back down in the range I wanted (9000 rpm for a 11x5.5).
If you look at my prop calculation thread, I believe (!!) it shows that switching to a larger prop (say like the APC12-6 E), and then adjusting rpm to get level flight speed back to where I like, that I won't really be using much more than I am with the 11x5.5. Of course when I pull the nose up and load the motor, the power draw should be higher with the 12-6 than the 11x5.5---which is what I want--more thrust to keep the airspeed from dropping too much. So this long winded explanation is that my max current draw with a 12x6 should be a a little higher.
Currently I run a Phoenix 35A ESC. I think it is ok for my application (but I am on the edge of it at peak power draw). I think your plane sounds a little larger, so maybe the 45A version is a better match.

2826-8 at 181g, 30 mohm is similar to a Scorpion 3026-8 at 189g, 20 mohm

I have to note that axi page state internal resistance of ONE COIL instead of combined resistance. They are combined to triangels, so real resistance for calculations is 20mohm.
It means that IR of 2826/10 is 28mohm and IR of 2826/12 is 41mohm.

I measure all motors myself too, I found several surprises :-)

Hi Dennis,
It doesn't really have a strong effect on things: the system you propose will work just dandy. At this point, it is just us gear-heads ... I mean electron-heads fussing over details. The problem only shows up when you try to use calculations for detailed predictions of props, currents and the like. As it turns out, this just isn't an issue for most of us.

I like the Castle PHX 45 a bunch and recommend it.
As for timer/sequencers, I am working on what I hope will be a near ideal solution, foir the purposes of sale. It isn't ready for sale, so I can't recommend it.
There are a few timers available, and at this point, I like the older Zigras timer (the one with a potentiometer) but only if you replace the pot with a 10-turn unit on a set of wires. That will give you a nice friendly needle valve.
Like I said, there are several choices, some of which are so new that I haven't had the chance to try any od them, so I will hold my tongue.

Merry Christmas All!
Dean