Flight time is one of the first and most important parameters you check for before buying a drone. It makes perfect sense because drones with higher flight times give you more time in the air hence extend their usability. Drone flight time varies with manufacturer, model as well as battery condition. This Drone flight time calculator will help you accurately calculate your time in the air.
Most manufacturers advertise the flight time in their drone specs, but these are not always accurate because these timings are under standard load and lab conditions. In practice, loads change as you might want to add additional gears to your drone (prop guards, extra battery, bigger camera, etc.). In such situations, you might want to re-calculate your drone battery life or flight time. It is painful to lose your drone just because you ran out of battery without warning especially with most DIY self-assembled drones that lack sophisticated battery monitoring systems or smaller toy category drones like Propel Snap 2.0 that have limited software capabilities to accurately calculate battery timings.
The tool above is a simple calculator I put together to calculate the flight time using average current draw under actual load (total weight of the drone before takeoff) and your battery capacity and takes into account what kind of motors you are using (brushed or brushless).
I have tested this calculator on a few drones that I got the opportunity to fly and found this quite accurate.
Below I have explained how this calculator calculates the flight time in detail for those interested in the technical details.
How does drone flight time calculator work?
The drone flight time calculator is a simple tool that takes into account two parameters.
- How much weight the drone is carrying
- How big is your battery
A heavy drone with a smaller battery will have shorter flight time compared to a lighter drone with a relatively bigger battery. Do note that the battery size is measured in terms of its capacity (Ampare-hours) and not its size.
Before going into the formula to calculate the flight time, let’s defined a few variables that we will be using.
Total Flight Weight (TFW) = TFW is the weight of the drone just before take-off. It includes the weight of the drone itself, any added accessories, and most importantly the battery. For this calculator, we will be measuring it in Kg.
Average Current Draw (ACD) = ACD is the average current all the motors draw from the battery. We use average because the actual current draw varies greatly during different flight stages and depends on the mode of operation (full throttle flight draws more current than mellow flying). To take into account the variations, we use the average value. For this calculator, we will measure it in Amperes.
Power to Weight ratio (P) = We use ‘P’ to describe how much power the motors need to lift one unit of weight. It is basically a parameter that depends on how efficient the motors are. Brushless motors have a value between 80 & 120 watts per kg and Brushed motors have a higher value of around 150 – 180 watts per kg. The more efficient the motors are, the less power it needs to lift 1 kg of weight. In the calculator above, I have assumed the following values;
Brusheless motors = 100 W/kg, Brushed motors = 170 W/kg
Battery Pack Voltage (V) = The total voltage of the battery pack depends on the cells’ series configuration. The output voltage is always written on the bottom of the battery, and it remains fixed for the most part of the battery operations (it plummets greatly when the battery discharges below a certain point, see battery discharge profile chart)
Battery Capacity (C) = The capacity of the battery is its ability to store electric charges. A higher capacity battery will be able to provide continuous electric energy for a longer time. The battery capacity is also written on the pack and is denoted in milliampere-hour (mAh).
Battery Discharge Margin (BDM) = It is highly recommended that the battery should never be discharged completely. Doing so will not only lessen its life, but it also puts your drone at risk of falling out of the sky dead if the battery suddenly plummets. For this calculator, I have put a default value of 80% which means, we will only use the 80% of the total capacity to calculate the flight time and keep 20% as a safety margin. You can change the value using the slider.
Flight time calculation
First, we are going to calculate the average current the motors will be drawing from the battery to support a the total weight. We will use the below formula.
Average Current Draw, ACD = (Total Flight Weight, TFW) x (P/V)
Once we have the average current, we will just divide the total available capacity ( C) of the battery by that current and we will have the flight time in hours.
Flight Time, T = (C x BDM) / ACD
Note: If you use mAh as a Capacity unit and Kg as your unit of weight, you will get the time in Hours. Just multiply your answer with 60 to convert it to Minutes.
If you find this calculator useful, please feel free to share it with your friends. If you have any suggestions, you can reach out to me at ahmed (at) flythatdrone.com