Mar 14, 2010, 02:42 PM  

Discussion
How do I work out how many Watts I'll get from my setup...
Just a quick general question here. Its mostly likely been asked before and I'm most likely to have been told already. But my mind doesn't hold onto equations too well at the best of times. So, can somebody outline the basic maths behind this problem so I/we can have it for a point of reference in the future when I/we inevitably forget it again!
Lets say I have a 50", 5lbs model that I'm looking to power. I know roughly that I'd need a motor with a max rating (for 15sec) of 600watts to achieve 100+ w/lb, but how do I figure out how many watts I'd be getting constantly and not just at this Max peak? I'd also like to know how I can figure out what amp rate speed controller I'd need to use, based on using a 3cell 3300mah lipo. I believe this is how I work out the basic amp draw : 600w ÷ 12.5v (3 cell lipo) = 48amps But my issue is that this is only the stated max watts for the motor for 15seconds. Its the constant output I need to figure out, that way I can get a better estimate of my amp draw and thus what size speed controller to use. Of course prop size comes into it too, but how and at what point in the equation? Any clear help on this would be most welcome, maybe it can even become a sticky....unless there is already a sticky showing how to work out all these things (watts, amp draw, estimated duration etc) and I've just missed it. Stuart. 
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