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Should this setup work on 20c 2250mah Batteries

Old 05-17-2008, 08:41 PM
  #1  
lvmitchell
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Default Should this setup work on 20c 2250mah Batteries

I have a 3D Hobby Shop Velox 3D plane weighing in at 43 oz. The motor is a Motrolfly DM2815 1100 kv swinging a 12x6 APC thin Electric. The speed control is a Suppo 40 Amp. I fly at half throttle plus or minus with few short burst of wot. At the end of 4 minutes of flying the speed control is just barely warm and the motor is cold. The battery is slightly warm. So given these facts it is obvious to me I am not pushing things to hard. But none the less I seem to be puffing the lipos I have more frequent than I think they should. I have a couple of 2250 mah 20C Looongmax batteries coming next week. My question is, treated right, should these batteries give me descent run times. (6-8 minuites) and not puff after just a few cycles. I try not to run my batteries down to less than 3.2 volts per cell. My speed control cuts off a 3 volts per cell and I very seldom fly that long. I here of people fly planes the same as mine on 15c batteries and getting run times of 8-10 minutes. I am just confused why I am not getting the same performance. Thanks for the help.
Lee Mitchell
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Old 05-17-2008, 09:57 PM
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Dr Kiwi
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You are on the recommended limit with a 12x6 on 3s, and I assume approaching the 38A max. The 20C 2250's should cope with that and if you really are using only half throttle (say no more than 20A average), you should get close to 6-7 minutes.
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Old 05-17-2008, 11:39 PM
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rcers
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Lee - "20c" claims are often exaggerated and you will learn that batteries are NOT created equally. Some cope well with 18-20c but very few in reality do - at least for any reasonable life cycle.

I know with the Velox you are are trying to keep it light for the tumbles, but you might try some larger capacity cells - or perhaps try several other brands.

But note that even with Name brand batteries, some are good some are not. I find myself sticking pretty closely to a cell size from a manufacturer that I know work. For example the TP Pro-lite 1320's and 2100's are some of my best performing packs. I never exceed 10-12c on those 15c packs and they perform wonderfully and last very well.

I have some 20c packs that lasted 20-30 cycles at 14-15c so I know your frustration....

In fact I find myself more and more using packs at 10c-12c max - and use larger capacities when higher draws are needed (and yes taking the weight hit....)

You might also consider using 4s A123's as well - they laugh at 40 amps and you can abuse them, charge in 15mins and I know of a couple of guys using them in the Velox with great results.

Mike
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Old 05-18-2008, 01:02 AM
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lvmitchell
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Could steping down in prop size help my situation. At this point
I am not trying to fly it maxed out 3D style. I am still learning to fly with some mild Harriers and knife edge. Does not take a lot of power for that. Would a 11x7 be a better chioce?
Lee Mitchell
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Old 05-18-2008, 01:08 AM
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Balil
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i would try the 11x7 prop w/ the 1100mah pack and see if your flight time increases on that, if it does. throw the larger capacity pack in there.. this way you know you're not pushing your electronics to the max anyways, ya know.
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Old 05-18-2008, 02:31 AM
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rcers
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Originally Posted by lvmitchell View Post
Could steping down in prop size help my situation. At this point
I am not trying to fly it maxed out 3D style. I am still learning to fly with some mild Harriers and knife edge. Does not take a lot of power for that. Would a 11x7 be a better chioce?
Lee Mitchell
Hard to say - what is the amp draw with that prop?

Likely not a huge difference between that and the 12x6....
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Old 05-18-2008, 03:44 AM
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lvmitchell
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I think I will go and get me a watt meter. Is that something the lhs will carry for the electric car guys. Anyone have a favorite watt meter they like? Once I get the watt meter how will I know which prop is the best for my setup. Just look for the one that pulls the least amount of amps and still gets my plane in the air?
Lee Mitchell
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Old 05-18-2008, 03:21 PM
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rcers
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Lee you are in the dark without a meter - that one piece of equipment will save you batteries, ESC's and motors.

Here is a good article that links to some good ones:
http://www.rcgroups.com/forums/showthread.php?t=311574

MIke
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