If you're in the market for a DJI drone, one of the factors you're probably considering is the battery life. The performance limit and overall capability of a drone are largely dependent on its battery life. Battery life is an important consideration because it'll largely determine what you can and can't do with a drone.
For the purposes of this article, when we talk about battery life we're referring to the drone's maximum flight time with a battery that's fully charged.
To save you some research, we've compiled a list of the maximum advertised flight times of DJI's most popular drones.
- Spark: 16 minutes (in flight); 15 minutes (hovering)
- Mavic Air: 21 minutes (in flight); 20 minutes (hovering)
- Mavic 2 Pro: 31 minutes (in flight); 29 minutes (hovering)
- Mavic 2 Zoom: 31 minutes (in flight); 29 minutes (hovering)
- Phantom 4: 30 minutes
- Inspire 2: 23-27 minutes (depending on which camera is attached)
Real Life Expectations
It's important to point out that these are just the advertised maximum flight times. In other words, these specifications are what these drones are capable of in optimal conditions. Keep in mind, you'll virtually never find such conditions in the real world. Drone manufacturers get these numbers by flying their drones in perfect conditions.
In reality, a host of factors will determine the maximum flight time that you'll actually experience. We'll talk about some of the biggest factors that will determine your battery life.
Factors That Affect Flight Time
When it comes to battery life and flight time, there are a few factors that come into play.
Hovering vs. Moving
Hovering actually uses more battery power than flying the drone at a slow to moderate speed. In order to hover, all of the motors have to run at virtually the same speed, which drains the battery faster.
When hovering in the wind, the speed of the motors constantly fluctuates to correct the drone's position. This frequent speed fluctuation, though slight, adds extra strain on the battery. This is why some drone manufacturers include a separate flight time specification for hovering.
When flying slowly or at a moderate speed, the front motors slow down to allow the aircraft to move in that direction. This reduction in power to these motors helps the drone operate more efficiently.
Though it might seem counterintuitive, the drone runs more efficiently when in motion.
It's important to keep this in mind when you're flying. If you let the drone sit still in the air for long periods of time, expect your battery to drain faster than it otherwise would. And if the drone spends more time moving at a moderate speed compared to hovering, its flight time will be slightly prolonged.
Wind speed is another factor that influences battery life.
Like we mentioned, stronger wind gusts force the drone to frequently change the motor speeds in order to keep the aircraft balanced and upright. A hovering drone is already less efficient, but this inefficiency is significantly exacerbated when wind gusts force the motors to change speeds. In short, strong winds force the drone to perform a strenuous balancing act that can quickly drain the battery.
Wind can also adversely affect a drone's battery life during forward flight (or in any direction). If you're flying against a strong headwind (wind blowing in the opposite direction that the drone is flying), the motors will have to spin faster to maintain the same speed. The stronger the headwind, the faster the aft motors have to spin to propel the aircraft forward.
Conversely, flying with a tailwind (wind blowing in the same direction that the drone is flying) reduces the strain on the motors. Think of a tailwind as force that's helping to push the drone in the direction it's going. With a tailwind, the reduced stress on the motors helps prolong the life of the battery.
Be mindful of the wind when you fly; if it's more windy, be sure to frequently monitor your drone's battery life.
Temperature can drastically affect battery life for a couple reasons.
By default, hotter temperatures cause battery life to drop faster. Higher temperatures simply strain the battery more than lower temperatures. Thus, flying in hotter environments will shorten the flight time of your drone.
The other reason that temperature impacts flight time has to do with flight physics. When air is colder, the air molecules are more densely packed together. In other words, the colder the air is, the greater the quantity of air in any given area.
Conversely, when air is hotter, it's less dense. In other words, the hotter the air is, the lower the quantity of air molecules in a given area.
So how does this affect battery life? To understand that, we need to understand that, simply put, the amount of lift that the drone's prop can generate depends on the density of the air and how quickly the prop moves through the air. Since the props on drones have a fixed pitch angle, the speed of the props is the only thing that controls the amount of lift generated.
So when the temperature is higher, the drone's motors have to spin faster than they do when the air is colder in order to generate the same amount of lift. In simple terms, the drone's motors have to work harder and spin faster when it's hot. As a result, the battery drains faster and flight time is reduced.
It's important to be aware of how the ambient temperature will affect your battery's life. If it's hot, expect for your flight time to be reduced.
In general, when flying in hotter environments, it's a good idea to only fly each battery until it has about 40% power left. When you reach 40%, land the drone, swap batteries, and put the old battery somewhere to cool off. Once it's cool, you can fly the remaining 40%. This will maximize your flight time with that battery and prolong the longevity of the battery itself.
Flight mode is another factor that affects flight time.
Generally speaking, DJI drones have a normal flight mode and Sport Mode. Sport Mode allows the drone to fly much faster.
Flying in Sport Mode will reduce your battery life much faster than flying in the normal flight mode. Earlier we mentioned that drones are more energy efficient when moving, but this is only true up to a certain speed threshold; once a certain speed is reached (that exact speed will vary from drone to drone, and the exact specifics are beyond the scope of this guide), the battery begins to drain quicker.
In this way, drones are similar to cars. Cars are inefficient when idling (or hovering in the case of drones), and they have a window of optimal efficiency when moving. But as soon as a certain speed is reached, efficiency goes out the window.
A drone's motors have to work extremely hard to maintain faster speeds. The result is a shortened battery life and less flight time.
The most important thing to bear in mind is that, if you fly in Sport Mode, expect for your flight time to be reduced.
The age of the battery also affects the maximum flight time. As a general rule, the older a battery gets, the shorter its life will be on a full charge. This has to do with how much energy batteries can hold as they age.
Just keep in mind that, as your drone batteries age, their life on a single charge will gradually dwindle.
DJI has produced drones with extremely impressive flight times. With that said, it's important to keep in mind the different factors that affect the drone's battery life. As a drone pilot, you should be aware of these different factors each time you fly and plan your flights accordingly.