jdetray

Formula for Run Time

run time in minutes = (Battery Capacity in Ah/Motor Current in A) x 60

This is just a rough guide, and it requires that you know approximately how much current your power system draws. A wattmeter will tell you. The formula also needs your battery capacity in Amp Hours (Ah). Divide mAh by 1000 to get Ah.

The simplest method is to measure your current at full throttle and use that number in the formula. In reality, you probably won't fly at full throttle all the time, so your average current usage probably will be less than the full-throttle value. Also, a power system will often draw less current in flight than it does during ground testing.

So if you use the full-throttle current in the formula, it will generally give you a worst case flight time. Actual flight time will usually be greater.

I've included some examples below.

- Jeff


Here are some examples.

Example 1:
1500 mAh battery
power system draws 12A

1500 mAh = 1.5 Ah

1.5/12 x 60 = 7.5 minutes


Example 2:
1500 mAh battery
power system draws 18A

1500 mAh = 1.5 Ah

1.5/18 x 60 = 5 minutes


Example 3:
4000 mAh battery
power system draws 25A

4000 mAh = 4.0 Ah

4.0/25 x 60 = 9.6 minutes


Example 4:
5000 mAh battery
power system draws 25A

5000 mAh = 5.0 Ah

5.0/25 x 60 = 12 minutes