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Archive for June, 2015

LiPo Battery Calculations

Posted by Mowee | Jun 19, 2015 @ 02:29 PM | 5,328 Views
You need to know the wattage or amp draw for your motors at 50% hover and what the maximum rating is as well. (the 50% number will change depending on weight load and props used)(A watt meter may be useful here)

If your using 4 motors that draw 22 watts each at 50% throttle.
This would be 88watts draw continuous at hover.

I you then divide the watts by the nominal voltage of your pack you get the amp draw of your motors.
88Watt / 11.1Volts = 7.9Amps draw.

You then calculate what the battery your looking at can supply continuous.

In this case we will look at a 5200 10C cheap battery first.
5200mAh / 1000 = 5.2A x 10C = 52A
This battery can do 52A continuously.

You then do the following calculation to see what percentage of this your copter is using. I rounded 7.9 up to 8
8Amps / 52 amps = 15%
So if your copter is hovering at 8A your using 15% of what the battery can do. This is really good but not the full picture.

What happens when your not at hoover and your using 85% or more of throttle? Lets calculate what would happen with the same setup pushed to 100% use.

The motors in my example would go from 22 watts each to 90 watts each.
So the same calculations would give you this.

90W x 4 = 360W total
360W / 11.1V = 32.4A draw at 100% load.
5200mAh / 1000 = 5.2A x 10C = 52A (Same battery)
32 amps / 52 amps = 62% of what the battery can do.
Would it work? Yes, but this would hammer the battery and likely lead to major...Continue Reading