Maximizing Multirotor Battery Life
Battery life is perhaps the greatest limitation for multirotors. Even with a very large, heavy, and expensive high-capacity battery, most multirotor aircraft will struggle to get ten minutes of flight time. Now, even five minutes of flight time seems much longer when you are out in the field, but nonetheless, as multirotor pilots, squeezing every last second of flight time out of our batteries should be a major focus of our time and energy. This page covers the things that most severely impact battery life, which also represent the best opportunities we have for improving the battery life of our multirotors.
Now, this page focuses on improving battery life without simply purchasing a larger-capacity battery. As discussed in the Selecting Batteries guide, as the capacity of lithium polymer batteries increases, their price and weight increase even faster. So replacing your current battery with on that has twice the capacity will likely cost you four times as much as the original battery.
By far and beyond the most important consideration for the flight time of multirotor aircraft is their weight. Obviously, the heavier the craft, the harder the motors must work to keep the craft aloft. Therefore, making our multirotor aircraft as light as possible is extremely important for improving flight times. Fortunately, there are a many, many ways we can reduce the weight of our multirotors:
- If you have the money, you can select components for your multirotor that are specifically designed for lightness. These components are often more expensive than standard components since they are often made from more expensive materials, like carbon fiber instead of plastic, or aluminum instead of steel.
- Remove unneeded components/equipment. For example, if you have a multirotor equipped with a camera for aerial photography, but on a particular day you only want to do some sports flying, remove the camera from the multirotor. This will save weight and improve battery life.
There are many reasons to make sure your multirotor props are as well-balanced as possible: it reduces wear on your craft, it improves video quality, it increases maneuverability, and it also improves battery life. While some of the energy we put into the props will always be wasted on fighting friction, we do not want to waste any more energy than necessary by using it to vibrate the multirotor. So balancing the rotors means more of the battery’s energy is used to generate lift and less is used to generate vibrations.
The KK2.1 flight control board used in the tutorials on this site has a feature called “Self-Level Mode.” When flying in self-level mode, the flight controller attempts to keep the craft level while performing various maneuvers. This feature is fantastic for shooting aerial videography, or for beginner pilots, but it does use more power than flying in standard mode. This is because in self-level mode, the quadcopter is constantly fighting its tendency to tip during maneuvers. This struggle against gravity and inertia uses more power.
Almost all electronic speed controllers have a feature called motor braking which controls the way the motors are allowed to slow down after the throttle control is reduced or zeroed out. There are two ways for motors to slow down: they can be allowed to slow down naturally under the influence of friction, or they can be stopped in their tracks by deliberate action by the ESCs. This second option is called motor braking and while it allows more rapid maneuvering during sports flying, it also uses more power. In order to stop the motors from spinning since the ESCs must expend energy to fight the inertia of the rotor. So, disabling motor braking will increase battery life.
Flying in windy conditions, although it is sometimes unavoidable, is tricky because we as multirotor pilots, must constantly correct for the wind blowing our crafts around. Unfortunately, the many small course corrections add up to a lot of extra work for the motors. This means that flying in the wind requires more battery power than flying in calm conditions.