Lipo capacity ?
 

Gentlemen,


It's crunch time on my winter project. Time to pick out a new
lipo for my E-Cub. Here is a list of my components,

GP rim fire 35-36-1200 motor

GP SS-60 Esc (60 amp)

GP E-Cub


I am stumped on what size mAh lipo to consider. I will be using
a 4s (14.8 V). Weight should be around 3 pounds (all up).
Looking for at least 10 minutes of flight time. Thanks for all input,


Bob

dignlivn

RE: Lipo capacity ?
 

Bob, You'll need to add the prop info to get any kind of response. No way to know your amp draw on the set up with out that.

Might also look at any of the calc programs out there for help too. You can plug in your specs for motors/props/esc/ packs, and play around and get a general idea of your flight times.

MotoCalc has a free 30 day trial, and there are quite a few others out there too.

p.s. if need be PM me your specs on everything and I'll be more then happy to run it on my calc programs for you.

RE: Lipo capacity ?
 

G.G.


Thanks, I'll learn this E stuff someday lol. The specs from the motor
show a Prop range from 9x4 thru 11x5.



Bob

RE: Lipo capacity ?
 

I'm gonna come at it a different way Bob -

AUW - 3lbs.

I'm estimating you need 50w/lb for cruising flight - therefore 150W

With 4s A=150/14.8 = 10 (or close enough) - so you need to draw 10A to cruise (or 10000mA). Therefore in 12 minutes you will consume about 2000mAh (12 mins is 1/5 of an hour and 2000 is 1/5 of 10,000).

Caveats:

I'm taking a guess at how much power you need to cruise - 50W per pound seems safe but ymmv.
This is all at cruising speed. If you go loud on the throttle you could probably divide your flight time by 2-4 (so somewhere between 2.5 - 5 minutes).

So maybe if you wanted some space to spare somewhere around 2500-3000mAh.

RE: Lipo capacity ?
 

ozrcboy



Thanks for the input and suggestions. I have been thinking
3000-3200 mAh's myself, just not sure about how to do the
math lol. Also, I think I over killed on my motor size for this
weight/size aircraft.


Bob

RE: Lipo capacity ?
 

Bob, I ran it on MotoCalc, using an APC prop. Also used a 4 cell 2500/ 20C pack.

It showed with a 9x4 the set up would pull 31.7 amps, provide 56.5 oz of thrust and a prop speed of 54 mph. Run time of 4.5 min.

On the 11x5 specs were as follows, 34.9 amps, 54 oz thrust, and prop speed of 42.5 mph, and a run time of 4.14 min.

Did warn that temps on pack would be getting up there unless it had good airflow over it.

BIG NOTE: Take this with a grain of salt, the only way to be sure is to check the set up with a meter at wide open throttle to get an accurate amp reading.
Then you can check against the calc program, and also verify if your pack is going to give you what you want, or what you are going to need capacity wise to meet your demands.

RE: Lipo capacity ?
 

Thank you Sir. I'll do just that.


Bob