It is a common fear of many drone pilots – running out of battery mid-flight. What happens when a drone runs out of battery? Does it simply fall out of the sky? Does it land in an automatic way? Or is there something else going on in terms of software and hardware that can keep your drone safe from damage when the battery runs out? In this article, we are going to have a look at what happens to different sorts of drones when the battery runs out and tips and tricks for making sure that you are never caught in this unfortunate predicament.
When a drone runs out of battery two things can happen. Firstly, the drone can decide to auto land or return to home (common in drones like the DJI series). Secondly, the drone can simply fall out of the sky because it doesn’t have enough battery power to keep the motors running.
Whichever of these options happens with your drone you should always try to land your drone safely well within the lifetime that is left on your battery. For many types of drone there is no excuse for letting the battery run completely dry as there are real-time on-screen display metrics that reveal your battery percentage and some drone manufacturers even calculate the point at which you should return to your takeoff spot.
Lithium polymer batteries are the battery that the drone community had been waiting for four years. They have a no leakage electrolyte (so they got a good storage life) they have a high energy density, they have a flexible geometry and are very safe to use.
However, lithium polymer batteries also need to be treated with respect and stored properly. If you do not follow simple lithium polymer maintenance and care routines the battery can quickly degrade. Things like exposing the battery to high temperatures as well as allowing the drone battery to be depleted to 0 can negatively impact the battery life and performance. Later in the article we will have a look at the best ways to store your batteries.
What happens when a drone runs out of battery?
What happens to a drone when it runs out of battery is dependent on how much you have spent on your drone. For the sake of this section we will look at high end and lower cost drones. For example, the higher cost drones are the consumer range drones typically purchased from manufacturers like DJI and Parrot. While the lower cost drones are those without any automated flight features or advanced hardware additions like sensors and GPS.
High end drones
High end consumer drones will typically have a whole range of automated flight features and functions. In this subsection of drones we have drones like the DJI Mavic air 2, the Phantom series drones from the same manufacturer and other drones like the parrot Anafi and those made by Autel and Yuneec. These drones typically cost in the order of $1000 plus.
Because you have spent so much on this type of drone the manufacturers have created a load of failsafes within the software and hardware. If you are coming close to the battery lifetime during a flight you will be warned by the software and the app. If you decide not to return home the drone will auto return to home (RTH) and some of the drones will also avoid obstacles on their way back to the landing spot. If you allow the drone to do this it will almost certainly return to home safely.
Unfortunately, as the pilot you can decide to cancel any of the automated return to home features. This means that it is still possible that you could ignore all of the warnings and not returned to home with enough energy in the batteries so that you fall short. You can also dismiss any warnings and noises which puts the drone at risk. An example of what happens when you ignore these warnings is shown in the YouTube video below:
if you don’t listen to the warnings you will almost certainly end up in quite the predicament. Hopefully you don’t end up getting wet like the poor chap in the video above.
Top tip: If you are flying over water equip your drone with floats
If you are flying near or over a body of water it may be useful to equip your drone with floats. These floats will protect your drone if you had to land on the water and do not add too much weight or drank while in flight. It would have certainly helped in the video, above.
Floats are relatively inexpensive and you can find them for a range of different types of drones. Have a look on Amazon for floats specific to your drone by clicking here.
Lower cost drones
Lower cost drones do not have any of the advanced return to home features that we see from their expensive counterparts. They have no return to home, sensors, or hardware to protect your drone.
Because they don’t have any of this advanced technology this is the worst-case scenario for your drone. It will simply fall out of the sky or descend quickly as the battery power is rapidly depleted. There is no promise of a soft or safe landing if you buy a drone that does not have return to home or a low battery warning. There are a bunch of apps that have on-screen displays and you should be familiar with what your app can tell you about the battery life.
These are my quick checks that I perform to make sure that I don’t run out of battery.
How to make sure that your drone doesn’t run out of battery
In this section we are going to have a look at what you can do to make sure that your battery doesn’t run out of juice at the most important times.
Charge them up the night before
Firstly, you need to make sure that the drone battery is charged up completely the night before your flight mission. If you notice any issues with the battery charging you should not use that battery for the flight the next day.
I like to go out with at least two batteries which have been charged within the last couple of days to ensure the I have enough flight time to do what I need to. The issue is calm when you are running out of juice and you have got an idea for a new shot all you want to perfect a shot you have already taken.
Never try to squeeze more timeout of a drone battery than is sensible – prepare to swap out the battery even if you feel like you could make the changes to your mission with the amount of voltage left in your battery.
Always launch with a fresh battery
You should always launch with a freshly charged battery. Launching with a freshly charged battery is one of the best ways that you can assure that you can get everything done in the 20 to 30 minutes flight time that you have. Even if I land early, I will always swap out the battery for a fresh one if I need to take off again. This is because I have now got a feel for how much flying I can get done during my drone flight and I could easily slip into autopilot and forget that this battery has less voltage than I am typically used to.
As silly as it sounds, in my experience, it is always the silliest mistakes that can cause you the biggest issues. And this is one that I can control.
Replace old batteries
You should aim to replace your batteries every 500 – 12000 cycles. That is because the lithium polymer battery degrades each time that you charge and discharge it. There are a few charging and the charging cycling protocols which change the depth of discharge so that you can improve the cycle life of the battery. But, quite simply, most of us are not disciplined enough to go through a rigourous cycling process during the charging and discharging of our drone batteries. Therefore, replacing old batteries once you start to notice that they are not performing as well as they used to will save you from running out of charge quicker than you think.
Look after your batteries
One of the most important ways of ensuring that you don’t run out of charge and that your batteries last is to look after your lithium polymer batteries properly.
Here are the best ways that you can look after your battery:
- keep them clean and dry – store your batteries and a clean and dry area which doesn’t have any excess moisture or dust. If the battery comes into contact with moisture it can easily rusting crow the contacts.
- Let your batteries cool before charging – after flight you are probably eager to get back up in the area soon as you land. But charging up your drone battery as soon as you land is not a great idea. That is because the batteries discharge a really massed rate and all this movement of electrons cause a lot of heating. Wait about 20 minutes before charging again this will protect the battery from overheating.
- Store at 50% charge – never leave your drone battery is fully charged if you are storing for a long period of time (over a month) is best to leave your batteries at 4.9 V per cell if you’re not planning to use them within a week. Smart batteries will often discharge themselves so that they reach the 3.9 V per cell stop
- Cycle the lithium polymer batteries after their first use – if you have purchased a new battery you should cycle the battery couple of times to help increase longevity of a battery. After an initial couple of cycles you can repeat this every few months which will combat something referred to as “battery memory”.
Get familiar with your app
Lastly, you should get intimately familiar with how to the app for the drone displays the amount of battery that is left. On the DJI GO4 app it is a long bar at the top of the screen which slowly moves down. In other displays, such as heads up displays, it is shown as a single number and could include the discharge rate as well.
Getting familiar with how your app displays your battery will be the best thing to help you prepare and plan to return home with enough battery. I always like to return home with a minimum of 15% battery left that way I will always be sure to have a little bit of buffer if my calculations are wrong.
Why do drone batteries die so fast?
If you want a long form article which talks about this in more detail go check out my other article – why does my drone battery die so fast? A guide to longer flights – click here.
Drone batteries die fast because flying a drone is a very energy intensive activity. It has to keep your drone in the air by displacing and forcing air downwards while also changing the motor speeds of the individual motors to keep your drone stable in the air.
Manufacturers report the flight time while the drone is in a hover. If you are moving around and you are combating environmental conditions, like strong winds, this can be significantly lower than your expected hovering flight time.
Your drone may be dying faster than usual because:
- You may be flying aggressively – if you are an aggressive flyer you are going to quickly deplete the energy stored in your battery. The drone has to accelerate against its own momentum which causes the battery to use a lot of energy.
- You are in sports mode – many drones use sports mode as a way to make the flight more interesting and nimble for the pilot but it will accelerate the battery draining time as the drone will move as quickly as it can to the movements of the joysticks.
- High winds – In high winds your drone will use up more battery as it is trying to stay in the same altitude and location. Just make sure that your outward part of your flight is into the wind so that you don’t have to fight the wind on the way back a common rookie mistake.
- Extra weight – you may be doing a little bit extra special with your drone like drone fishing or using a drone to lift heavy things. This extra weight can cause your drone to deplete its energy faster. Even little additions like full drone stickers and decals can cause a noticeable difference in your drone flight.
All of these things can cause your drone to deplete its battery faster than you are anticipating and could cause your drone to run out of battery mid flight.
Can I put a bigger battery in my drone?
Some consumer drones do not allow you to change the battery without opening up the drone body and avoiding your warranty. However if this is something that you are willing to do a bigger battery will allow you to fly for longer but it comes at a cost of more weight. This is a very tricky balancing act as there is a point at which the extra size of the battery out ways the amount of extra flight time you get. All because of the added weight.
In fact, the easiest way to increase the amount of flight time of a drone is not to add more lithium polymer batteries but rather to change the fuel source for another one.
One of the longest flight drone times ever recorded is four hours and 40 minutes. Given that the average drone can only hover for only half an hour this is pretty impressive. This record is claimed by Spanish drone manufacturer Quaternium. The drone uses a hybrid fuel source which includes an electric engine and a combustion engine. The combustion engine keeps the battery charged throughout the flight
The company’s mission is to:
Quaternium mission is to design the most advanced multirotor UAVs in the market. We combine experience and high tech to develop a disruptive product that aims to revolutionize the multicopter field. With this ultimate innovation, flight duration is increased 6 times compared to existing alternatives.
That’s pretty impressive and it’s is something that they seem to have been able to achieve. One of the current models of drones involves a two-stroke combustion engine that requires a 95 octane +4% oil mix. It also contains a lithium polymer battery. It can carry up to 10 kg and at a full load can stay in the air for approximately two hours. The cruise speed is 50 km/h with a maximum speed of 80 km/h. That’s a pretty impressive drone that has a load of potential applications where lithium polymer batteries alone will not cut it.
Which drone has the longest lasting battery?
Below in the table are some of the most popular drones currently available, their weight, flight time, cost, and how many dollars per minute of flight time that each drone has.
|Drone||Weight / g||Fight time / min||Cost US$||$/min|
|Mavic Air 2||570||34||799||23.5|
|Phantom 4 PRO V2.0||1375||30||1599||53.3|
|Mavic 2 Pro and Zoom||906||31||1599||51.6|
|Phantom 4 RTK||1319||30||5890||196.3|
|*based on last model|
We can see that the Mavic mini has the lowest cost per minute flight at $13.30 per minute of flight time. Closely followed by the Parrot Anafi as well as the Mavic air 2.
So, if your drone runs out of battery mid flight you are immediately going to thank yourself for purchasing a drone that is a little bit more expensive stop this drone will return to its takeoff spot with no issues whereas a cheaper drone will crash and land close to where it runs out of battery.
Happy drone flying and I hope that you never have to deal with a unexpected depletion of your drone battery!