# Electric Power Systems for a qudrocoper base on 30amp Speed Controller and NX-4008-620 - NX-4008-620kv Brushless motor

I'm in mood to put together my own quadrocopter. Just before I ordered parts wanted to some experts to tell me if configuration if compatible enough. Or maybe you have better suggestions for this motors? Actually i'm not shure about battery. Will it handle this 4 motors? So I put in my cart:

ZIPPY Flightmax 4000mAh 3S1P 20C

Capacity: 4000mAh
Voltage: 3S1P / 3 Cell / 11.1v
Discharge: 20C Constant / 30C Burst
Weight: 306g (including wire, plug & shrink wrap)
Dimensions: 146x51x22mm
Balance Plug: JST-XH


 Kv: 620rpm/v
Turns: 16T
Resistance: 0.129Rm
Idle Current: 0.8A
Can size: 45mm
Can Length: 14mm
Shaft: 3mm (Includes Prop saver mount for GWS style props)
Suggested ESC: 30A
Rated Watts: 180W
Weight: 79g
Cell count: 3~4S Lipoly


TURNIGY Plush 30amp Speed Controller

Cont Current: 30A
Burst Current: 40A
BEC Mode: Linear
BEC : 5v / 2A
Lipo Cells: 2-4
NiMH : 5-12
Weight: 25g
Size: 45x24x11mm


This is from an EE and not an RC perspective
For actual in the fuield performance you want to ask RC people as it's really how well the products match their claims.

People seem to like the flightmax OK. 20C = 20 x 4 = 80A.

BUT Motor is rated at 180 Watt.
Power = Watts = V x I
or I = V/P
As V drops P will drop and a claimed 180 W is probably at full charge.
I'll assume that.

IF you want to run this at full power you need I = P/V = 180/11 =~ 16+ A.
Four at full power ["Pull up! Pull UP !!!!!!!"] = 64A. The battery will be getting exercised at 64/80 = 80% of continuous rating but bearable IF they meet specs.

But that's more than double the ESC continuous and still 64/40 = 160% of burst rate.
The ESC is liable to burst when run above burst for more than about no time.

They recommend a 30A Esc for one motor so if you followed that you'd want about 120A ESC for 4 motors. I'm not aware of the technology so I don'y know if you get 1 channel per ESC or 4 in one unit. This is OK for one motor but not for 4. At a minimum you want about double the gross ESC capacity.

There should be relatively little in greatly boosting ESC power. Pretty much just bigger MOSFET(s) and a bigger heatsink. 16A at 10 milliohm Rdson =~ 2.5 Watts = modest heatsink. That's a very capable MOSFET. At say 50 milliohm on and 16A you get I^2 x R = 256 x 0.1 = 26 Watts = hot !!! Good FETs wanted. And leads, connections etc.

You could always limit it to what the ESC is happy with but power would be well down on what the 4 motors together are notionally capable of.

• I gonna use 4 ESC. So if use 4 ESC do i need battery with higher 4000mAH? Will my 80A of batteru curent split on 4 ESCs? – Pol May 30 '12 at 16:31
• 4 x ESC is OK. Battery says 20 x C rated. 1 x C = 4000 mAh = 4 A. So 20 C = 80A so battery is OK. – Russell McMahon May 30 '12 at 20:11