Eagle Tree graph of 450SE on 3s A123

[Bill Sanford]

WOW!

See attached Eagle Tree graph of the following setup.

TRexSE
Scorpion HK2221-6
Phoenix 35
6V Park BEC

I was surprised to see peaks of over 400 watts and 50+ amps.
I guess I may have to invest in a bigger ESC!

Got to love the A123 cells!!

Bill

[Sandy]

What kindof head speed were you able to achieve?

[Bill Sanford]

Just tached it the other day and it was at about 3050 in a hover. I run governor mode, but with not too much headroom...

Bil

[DominicD]

You have a eagletree and you DONT use a HS sensor ?!?!?!

[Bill Sanford]

Originally Posted by HFG

You have a eagletree and you DONT use a HS sensor ?!?!?!

I'm into gadgets as much as the next guy, but at some point you just have to put away all the toys and fly the model!



Bill

[DominicD]

The HS is the most important sensor, you can diagnose most problems from the response of the HS.

[Bill Sanford]

Originally Posted by HFG

The HS is the most important sensor, you can diagnose most problems from the response of the HS.

I would tend to disagree. You can hear head speed changes, but amp draw and voltage can't be guessed at. I think these things are much more important in my book, especially if you have an optical tack to give you a HS reference point.

That being said, plotting head speed would be nice, but I don't see it as a necessity.

Bill

[DominicD]

An optical tach is pointless for the most part. Your really only taching the head at one point which is usually in a hover. The information iam talking about is about how the HS responds to changes in torque. The power and current draw only serves to peak your interest, doesn't really provide a whole lot of useful information.

[Bill Sanford]

Originally Posted by HFG

An optical tach is pointless for the most part. Your really only taching the head at one point which is usually in a hover. The information iam talking about is about how the HS responds to changes in torque. The power and current draw only serves to peak your interest, doesn't really provide a whole lot of useful information.

I think amp draw is the #1 need for an Eagle Tree and critically important for both performance and the life of your power system. Voltage is also important to see how well your batteries are doing under load. You can easily see and hear bogging and HS loss.

I guess we agree to disagree. To each their own...

Bill

[write2dgray]

Very nice Bill - thanks for sharing! I agree amps are probably most important, but only when combined with temp, volts, and headspeed .

Not too many running LiFePO4 on 450 helis due to the weight hit. 3S is a little low on the voltage for most and 4S is just too porky, but this shows that what it lack in V it makes up for in A, but IMO that is probably stressing the CC-35 a little bit too far...

- David

[Bill Sanford]

Originally Posted by write2dgray

Very nice Bill - thanks for sharing! I agree amps are probably most important, but only when combined with temp, volts, and headspeed .

Not too many running LiFePO4 on 450 helis due to the weight hit. 3S is a little low on the voltage for most and 4S is just too porky, but this shows that what it lack in V it makes up for in A, but IMO that is probably stressing the CC-35 a little bit too far...

- David

Hi David,

3S works just fine. I can't imaging flying with 4S A123 on a 450. You can feel the weight of even the 3S A123 pack compared to a 3S lipoly, but it's not much of an issue and the benefits far outweigh the slight weight increase.

Concerning the 50+ amps, you're right about pushing the CC-35, but I have three of them and will keep flying them until one gives up. Seriously, they actually run cooler than they did running 3S lipoly. Even in the 450 without the external BEC... I think this is mainly due to the lower voltage that the BEC has to regulate. The BECs in these things generate more heat than the actual ESC...

400 watts is plenty to make you smile in a 450 sized heli...



Bill

[ping]

Hi Bill,

Have you tried out the 1100 A123 cells at all in the 450? Seems to me like they would be a better fit to the airframe.

[Bill Sanford]

Originally Posted by ping

Hi Bill,

Have you tried out the 1100 A123 cells at all in the 450? Seems to me like they would be a better fit to the airframe.

The 1100 cells have less energy density per ounce, so it would likely not perform as well.

With the right kv motor a 3S pack of the bigger cells really works well. I won't go back to lipolys...

Bill

[JustPlaneChris]

I tried the 1100 A123 cells in my King V2 and was not impressed. They may have their uses in small planes, but for helis I think the larger cells are still the best way to go. There's no issue fitting 3 of the large A123s in a Trex or clone airframe:

http://www.rcgroups.com/forums/showp...postcount=1961

I've flown the heli pictured in that post, and it's certainly a nice setup for sport flying.

rvsixer's CopterX 450 (5 min 22 sec)

[Sandy]

I have not used the A123s, but use 3S lipos with the Scorpion-6(4400 k/v) and used gearing and gov to get the HS to around 3200 for about 4+ minutes.. My Beam comes alive wth this high HS..

Can A123s deliver this level of performance? I sure like the 30C continuos and rapid charge features of A123s..

[Bill Sanford]

If you want absolute maximum performance, lipolys do have better energy density. My head speed is about 3050 with the Scorpion -6 and a 13 tooth pinion, but the head speed will sag a bit more using A123 than good lipolys under heavy load.

That being said, because I'm only running a Phoenix 35 and peak amps are over 50, a Phoenix 45 or 60 would likely give me more power under load.

After flying the 3S A123 setup for quite a while, the main difference I feel is the bit of extra weight. Unless you're really in to hard core 3D, I don't think it's a big deal.

In my opinion, the benefits far outweigh the slight weight penalty.

I've also had a couple of BAD crashes that I know would have damaged a lipoly pack, but the A123s are super tough and are no worse for the wear..

Bill