This article will help you to calculate the flight time of your drone. You can experiment with various parameters to calculate the best flight time for your drone.
The drone flight time in hours is calculated by this formulas:
Drone flight time = capacity * discharge / average amp draw
OR
Drone flight time = capacity * discharge * voltage / (total drone weight * power)
OR
Drone flight time = capacity * discharge / (total drone weight * current)
where:
- capacity – It’s the capacity of your battery, expressed in milliamp hours (mAh) or amp hours (Ah). Please note that 1 Ah = 1000 mAh. You can find this capacity value printed on your LiPo battery. So, the higher the capacity, the more energy is stored in the battery.
- discharge – It’s the battery discharge that you allow for during the flight. As LiPo batteries can be damaged if fully discharged, it’s common practice never to discharge them by more than 80%. Basically you need to leave 20 % charge.
- average amp draw – It’s calculated in amperes. The average amp draw can be calculated based on parameters such as the drone weight or battery voltage, please use the formaula below:
average amp araw = total drone weight * power / voltage
OR
average amp araw = total drone weight * current
where:
- total drone weight – It’s the total weight of the equipment that goes up in the air, including the battery and measured in kilograms.
- power – It’s the power required to lift one kilogram of equipment, expressed in watts per kilogram. You can normally use 170 W/kg. Some more efficient systems can take less, for example, 120 W/kg; if that’s your case, don’t hesitate to adjust its value.
- voltage – It’s the battery voltage, expressed in volts. You will find this value printed on your battery.
- current – The power / voltage is the definition of an electric current I (in amps) required to lift one kilogram into the air. It comes from the Ohm’s law (power = current * voltage).
Remember that the time calculated might differ from the real flight time. We assume that your drone mostly hovers in the air – every time it performs any maneuvers, one of the motors has to work faster and hence uses up more current.
You can use the following numbers as a rule of thumb:
- If your drone only moves around slightly – for example, during aerial photography – the flight time will be about 75% of the calculated time.
- If your drone flies in strong wind or moves a lot, the flight time will decrease to around 50%.
- If you are participating in drone FPV racing or flying at high throttle levels, the flight time will decrease to 25-30% of the calculated value.
Drone flight time calculation example
Let’s look at the following example. We want our drone to hover in the air for 30 minutes to take an aerial video. Which battery capacity do we need for this job?
INITIAL DATA:
The maximum discharge of the battery is 80%, battery voltage 11.1V, total drone weight with payload – 2 kg, watts required to lift one kilogram (power) – 170 W/kg, drone flight time – 30 mins (0.5 hours).
CALCULATIONS:
The average amp draw calculated:
average amp draw = (total drone weight * power) / voltage = 2 * 170 / 11.1 = 30.6 A
The drone battery capacity calculated:
capacity = drone flight time * average amp draw / discharge = 0.5 * 30.6 / 80% = 15.3 / 80% = 19.1 Ah
Summary
We have learned in this article how to calculate the drone flight time, the average amp draw and how to estimate the capacity if other parameters already known.
Thank you for reading.
If you like to read more you can check other articles on our website:
EU DRONE PILOT PREPARATION FOR A1, A3 AND A2 EXAMS
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