Get Longer Flight Time on Multicopter

It’s hard to determine flight time on a quadcopter without actually testing it. Flight time depends on many factors including how fast the quad flies, battery capacity and weight, motor/propeller efficiency, payload, wind speed etc. However there are things you can do to maximize your flight time in the air.

When discussing about “flight time”, it’s important to understand it’s not “hover time”. Hover time is pretty much a constant value for a quadcopter with a particular battery. But flight time can vary depends on the throttle level and wind condition during the flight. That’s why you can’t really compare the “flight time” between 2 different multicopters, it’s not a fair comparison as it’s influenced by so many factors.

large_Quad_Copter_01

Generally speaking, low KV motors with large propellers have higher efficiency and can carry larger battery, and thus giving longer flight time.

But you don’t have to build a gigantic quadcopter to stay longer in the air. In this post we will discuss what impacts battery life, and some of the things you can do to maximize your hover time as well as flight time.

Throttle Management and Motor Efficiency

Efficiency of brushless motors tend to get worse with increasing throttle. Therefore fast and acrobatic flying will shorten flight time because using high throttle will consume more power.

If you only plan to do aerial photography and just want some more time in the air, the best thing to do is to fly gently and avoid unnecessary turns or throttle changes.

Weight – Payload

As you can probably guess, the simplest and most effective way of increasing your drone’s flight time, would be to reduce the weight. Every gram you shave can contributes a few seconds in flight time if not more.

Here are some idea how to lighten your quad:

  • Shorten motor, ESC and power wires as much as possible
  • Avoid using connectors and direct solder whenever possible
  • Remove HD camera (GoPro/Mobius) if you are not recording
  • Use light weight components and hardware

Battery

It’s obvious that the battery can directly affect the flight time of your drone, but it’s not as simple as it might seem.

Capacity

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, there is a trade off (balance) between capacity and flight time.

You can keep increasing the capacity of the battery, and gain longer flight time. But eventually the battery would become so heavy the quadcopter cannot handle it anymore and start to lose flight time.

The additional weight of larger battery can also affect your quadcopter’s flight characteristics, which you should also take into account depends on the type of flying you want to do.

You can experiment with batteries of different sizes, measure the hover time and find out which one gives the best result. Here is an example how I choose the optimal battery capacity (very old post).

flight-time-vs-battery-capacity1

C-Rating

LiPo Battery C rating does not only affect the max continuous current draw, but also flight time. Surprised? Let me explain.

lipo-battery-c-rating-affect-flight-time

Let’s assume, when you have consumed 80% of the battery capacity, the voltage drops 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. So during flight you might have only consumed 60% of the capacity, but the voltage is already at 3.5V. Although after landing the battery will annoyingly recover to a much higher level such as 3.8V.

You can have a lower effective capacity due to voltage sag. Also lower C rating battery tends to heat up more due to higher internal resistance, and heat is wasted energy in the battery.

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 diminish. 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

If flight time is more important than power for you, then by choosing an efficient motor and propeller combination will help immensely.

diy-simple-motor-thrust-measuring-stand-test-station-simple-example-1

Motor efficiency is 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 energy. For example the Cobra 2204 1960KV motors with 6045 propeller gives me more power than 5030 props, but I will get longest flight time with the 5030 thanks to the higher efficiency.

Here is a guide on how to choose mini quad motors and propellers.

Balancing your propellers can slightly increase your flight time too. Unbalanced propellers introduce vibration to your aircraft, and vibration means motors are changing their RPM very quickly which can use more energy than it should.

The smoother your quadcopter flies, the more power efficient it is.

 

PID tuning!

As mentioned earlier, vibration means more heat to the motor and more energy wasted. A well tuned, smooth, and stable multicopter is more efficient and gives you longer flight time.

Wind

When flying into headwind, you need to use 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.

Additional Components

Additional peripherals such as LED, FPV gear, camera gimbals etc can reduce your flight time, if they share the same battery as your quadcopter. Perhaps by a very insignificant amount. The biggest influence is the weight of these components.

Your video transmitter is one of the most power hungry peripherals, and can draw up to 0.5A at 12V for example, which is about 6W.

A motor on a mini quad can easily draw 15A – 30A at 16V, which is 240W to 480W. For 4 motors, that’s 960W to 1920W!

Emax-nighthawk-250-mini-quad-added-WS2812B-led-strip-underneath

So the VTX consumes less than 0.6% to 0.3% of the total power usage. Put that in flight time terms, if your flight time is about 5 mins (300 seconds), that’s about 1 second that you would lose.

But for sure, the weight of the hardware would have a much bigger impact on flight time. That’s why it’s important to use components that are as light as possible.

Edit History

  • Jul 2015 – Article created
  • Apr 2018 – Updated

9 thoughts on “Get Longer Flight Time on Multicopter

  1. Ole

    Hi Oscar

    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?

    Reply
    1. Oscar Post author

      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…

      Reply
  2. ZetEm

    Hi Oscar,
    yes, your LEDs and gear consumpt very low % of your battery, but you haven’t forgotten they increase weight of your copter

    Reply
  3. Will and Tracy

    Hi Oscar!
    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.

    Reply
    1. Oscar Post author

      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.

      Reply
  4. Bradley

    Hi Oscar,

    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 :)

    Brad

    Reply
  5. eephyne

    Very nice article as always. Really helping to figure out some elements to lighten the multi.

    Thanks Oscar

    Reply

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