Quadcopters aren’t the most efficient aircraft compared to planes and fixed wings, therefore they tend to have relatively shorter flight time. I will explain the many factors that affect flight time on a drone, and how to keep you in the air for longer.
It’s important to understand the difference between “flight time” and “hover time”. You can almost always get the same hover time on the same quadcopter and battery under the same condition. But flight time can vary considerably depending on how fast you fly and the wind is.
Having longer flight time is important to a long range FPV quadcopter.
Let’s dive into what affects flight time and how you can maximize it.
“Warming Up” Battery
As mentioned in this article, LiPo battery has the best performance when it’s around 35°C. In colder condition, your battery might appear to be less “punchy” and have worse voltage sag, which can result in shorter flight time.
Therefore it’s a good idea to warm up your batteries to its optimal temperature before a flight, for example, putting it in your pocket.
Change How You Fly
To increase flight time without touching any of the hardware, the obvious is to change the way you fly.
Every movement you make by touching those sticks on the radio transmitter, changes the rotational speed of the motors. When motor speed changes, more heat is generated and it uses up your battery more quickly.
If you just want more time in the air, the best thing to do is fly gently and avoid unnecessary turns. Having steady throttle management also helps.
Basically, the closer you are to hovering, the longer flight time you get :)
Every gram you save is a few extra seconds in the air.
In a heavier quad, the motors have to work harder and so the battery doesn’t last as long. By reducing the overall weight of a quad can improve performance too, making response more snappy and acceleration faster.
Here are some ideas to help your quad to lose some weight:
- Shorter XT60 pigtail, motor and ESC wires
- Avoid using connector, direct solder whenever possible
- Remove HD camera (GoPro, Runcam etc) when it’s not recording
- Choose light weight parts (frame, motors, etc)
- Use titanium and aluminium hardware over steel, but beware of the possible reduction in durability
I talked a bit more about the benefits of ultralight racing drones in this article.
Choosing Battery for Longest Flight Time
A larger battery provides longer flight time for your drone, but it’s also heavier which requires the motors to run faster. It’s a trade-off between battery capacity and weight.
Capacity vs. Weight
Battery capacity directly affects flight time. But interestingly, bigger battery doesn’t necessary give you longer flight time because the weight of the battery increases with capacity.
You can keep increasing the capacity of the battery and gain longer flight time. But eventually it will reach a point where the battery is simply too heavy for the quadcopter to handle, and it even loses flight time.
The additional weight of a larger battery can also affect your quadcopter’s flight characteristics, which you should take into account given the type of flying you plan to do.
For example, a 5″ acro mini quad can probably carry a 4S 3000mAh battery with ease. However the optimal choice for battery size has been proven to be 1300mAh to 1600mAh on 4S because pilots prefer the nimble and agile response.
You can experiment with batteries of different sizes, measure the hover time and determine which can give you the longest flight time. Here is an example how I choose the optimal battery capacity (very old post).
LiPo Battery C rating does not only affect the max continuous current draw, but also flight time. Surprised? Allow me explain.
Ideally, when you have consumed roughly 80% of the battery capacity, the voltage would drop to 3.5V per cell and this is normally when you want to land to avoid over-discharging.
However low C rating LiPo batteries tend to have much worse voltage sag. You might only have consumed 60% of the capacity, but the voltage is already at 3.5V. After landing the battery will recover to a higher level e.g. 3.8V. As you can see, batteries with poor discharge performance can limit the effective capacity and possibly give you shorter flight time.
Lower C rating batteries also tend to get hotter due to higher internal resistance, thus more energy is wasted in heat.
Battery Condition and Maintenance
This could well be a whole new topic, and there is simply too much to cover. But basically, your batteries will get old and the capacity they hold will start to decrease. It’s important that you keep them in good condition, avoid over-charging and over-discharging.
Here is a guide on how to use and look after LiPo batteries.
Motor and Propellers
it’s important to carefully choose motor and propeller combination depends on your need, such as power and efficiency.
Motor/Propeller efficiency can be calculated by dividing thrust by power, which is gram per watt (g/W). The higher g/W, the more thrust is generated at a given amount of power. For example the Cobra 2204 1960KV motors with 6045 propeller has a higher maximum thrust than 5030 props, but the 5030 propellers will give me longest flight time thanks to the higher efficiency on that motor and propeller combination.
Here is a guide on how to choose mini quad motors and propellers.
Fewer blades in a propeller are usually more efficient due to the fewer points of trialling vortices wasting energy.
Propeller balance is beneficial to flight time. Unbalanced propellers introduce vibration to the aircraft, which means constantly changing motor RPM and more energy is consumed.
Generally low KV motors with higher voltages is a better option towards longer flight time. Low KV motors swinging large propellers is another good option for higher efficiency. That’s why larger rigs usually have longer flight time.
I explained the benefits of 6S to mini quads, and if it’s actually more efficient than 4S.
As mentioned earlier, vibration translates into heat in the motors and wasted energy. A well tuned, smooth, and stable multicopter is more efficient and gives you longer flight time.
Check out my PID tuning guide for mini quad.
When flying into headwind, it requires higher throttle to move at the same speed, therefore shortening your flight time.
Wind can also cause instability to the quadcopter, and the motors have to work harder to stay level. This means that flying in windy weather can drain battery faster than flying in a calm day.
Should I be worried about the small components I have in my quad? Yes and no.
Additional peripherals such as LED, FPV gear, camera gimbals etc can reduce your flight time, but they draw so little power it’s usually not something to worry about (less than 1%). It’s the weight that has a more noticeable impact on flight time.
If you truly want to increase flight time, remove any unnecessary parts.
Less is more!
I hope the article has been useful. There are so many little ways that help increase flight time, maybe not by a significant amount, but they all add up.
- Jul 2015 – Article created
- May 2018 – Updated
- Nov 2018 – added info about temperature
Another good article, thank you Oscar.
I’d like to point out that while too low a C rating will adversely affect efficiency due to voltage sag, too high a C rating will also lead to significant inefficiencies. High C rating batteries use a lot more metal in their construction in order to reduce internal resistance under high current demand situations. Obviously the additional metal results in a heavier battery. So like everything in drones with respect to efficiency, there is a sweet spot with battery C ratings which will be determined by all the other parts selected.
I noticed a significant drop in flight time after changing my 5″ quad to betaflight 4.0. I cannot seem to figure out what causes it (filtering changes I’m guessing, but I wish I understood it.)
Oscar… You said “Basically, the closer you are to hovering, the longer flight time you get”
Actually a “medium” speed thru the air increases flight time because extra lift is generated for free by the wind moving past the blades…and it’s a substantial increase.
The is exactly the same as real helicopters. It takes much more power to hover than it does to fly (or likewise, to hover in place on a windy day).
when the quad is tilted, the motors have to spin faster to create the same downward force to keep the quad in the air, and therefore it will draw more current. And what you are describing is the best case scenario, what if the wind is blowing the opposite direction? it will drain the battery even quicker.
I got a question choosing prop.
I am choosing between 3 props. Will the prop that gives the most thrust give the shortest flight time?
flight time depends on prop/motor efficiency, also depends on how much throttle you apply during the flighyt…
Thrust is only part of the equation…
Hi Oscar, Ex heli pilot chiming in. What Bill was talking about with the wind is relative wind because of movement of the drone/heli (nothing to do with actual wind). It’s bit confusing for novices to physics and you will need to look up aviation textbooks to get better idea. Bill is right with the lower power requirements – hover and max speed flight need a lot of power and somewhere in between is the sweet spot where you have best balance between drag, lift and power – usually that speed is called optimal endurance speed (the most distance). There is also optimal cruise speed which will get you from A to B in the most economical way (the least use of energy)
yes, your LEDs and gear consumpt very low % of your battery, but you haven’t forgotten they increase weight of your copter
yes you are right :) someone mentioned it already in the comment
Long time reader of your excellent articles and tips, I am very grateful for what you do, so let me start with a humble Thank You. I’ve been curious about this topic myself for quite a while, to the point where I was performing hover tests and calculating results. While I don’t have the means to afford a motor test stand, I am blessed to have two almost identical ZMR250’s from Sitela, (you think that Cytryna PDB was complicated, look at the Sitela!), with which I have configured with different motors typical of the class (1806s from RTFQ on mine, and 2204s from EMAX on my fiancées). I thought that configured this way, with almost everything else being even, I could have a reliable gauge as to battery life.
I was incorrect, and still at a loss as to which setup is more efficient. We’re both running 5030s, 1400mah 40C 3S, 15A BLHeli motors, and Flip32+’s. 6 minutes is where our timers are set, and it seems we always return with 11.3V on both ZMR’s. Once I get a better gauge on their flight times, I can be a little more liberal with our timers.
Is there a general rule of thumb for the 250 class regarding 1806’s vs 2204’s? Or 5″ vs 6″ on 3S? I know your article was full of science, and here I am asking for generalities, but I thank you for your answer either way.
not really… efficiency really comes down to the motors and prop for mini quad… even the same size motor from different manufacturers would give you very different characteristics.
but anyway, i generally find mini quad motors around 2300KV, runs most efficiently with 5030/6030 props on 4S, with 3S, i think 6030 is probably better… but you need to test it really to confirm.
Just FYI BlHeli ‘Dampened Light’ is actually regenerative braking (ie uses the motor as a flywheel generator and sends the power back to the battery) meaning it actually recovers a small amount of energy when slowing the motor rather than just bleeding the power off through the FET’s like regular ESC braking does.
So theoretically enabling Dampened Light should actually slightly increase flight times especially when flying like Chad Nowak :)
Not true active braking is very ineffecient and the recovered energy is minimal compared to the reduced thrust from the braking effect.
If you want to increase flight time turn off active braking but it will make your quad fly much worse and be very hard to tune.
Nice article again. Thx
Very nice article as always. Really helping to figure out some elements to lighten the multi.