Help! Motor draw and battery capacity

HVB79

Member
The battery was about 80% charged.
Test with a fully charged battery. The fully charged battery will be at a higher voltage resulting in more amps.

At 70% throttle, the current was around 27A, and at 99% it was around 58A. The power on the meter was reading about 820W at 100%.
The spec sheet for the motor shows Power 710W. What is this for?
The 710W on the spec sheet are the maximum amps for the motor assuming maximum airflow for cooling. Running a 710W motor at 820W and it will burn out very quickly. My guess would be it would last about one min at 820W before burning out. Depends on how optimistic the rating is. You should limit your maximum throttle or use a smaller in diameter and/or pitch prop.

The spec sheet also shows the minimum prop should be 11x8.
This is incorrect. The spec sheet shows a recommended range of props to give you some idea what props size you could use. You can put any prop you want on it as long as you stay under 710W. Putting a smaller prop on it will not damage the motor.
 

messyhead

Well-known member
Thanks. I thought the 11x8 at 4s was to stay within the power rating.

I ran it with a 10x7, and it was 43A and 654W at 100%, with 90% battery. So I think I’ll go with that.

I also ran an 11x5, and it was 41A and 630W at 100%, but the battery was down to about 85% by then.

I think that 11x5 will be the ideal prop, but I’ll test it again at 100% battery before flying with it.
 

messyhead

Well-known member
I maidened the Nova tonight. She flew beautifully on the 11x5. I got 2 full 6 minute flights, cruising around at 55% throttle. The battery is was just over 3.8v per cell after the 2nd flight.

So I’m going to get some 11x5 electric props, just for the extra efficiency.
 
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