Types
Before we get into the nitty-gritty of drone batteries let's check out the two types used today. The most commonly used battery for drone quadcopters (commercial drones) is LiPo. LiPo stands for lithium polymer which is a battery chemistry that provides a higher battery capacity and higher discharge rates too. A LiPo battery usually has a 4.2 V voltage when fully charged and a nominal voltage of 3.7 V.
LiHV batteries, on the other hand, are known as lithium high voltage batteries that have a 4.35 V voltage when fully charged and a nominal voltage of 3.8 V. These type of batteries will provide the drone with more power in the beginning stages of its discharge but it will drop in voltage drastically at a certain point. This doesn't happen with a LiPo battery for drone, as it provides a steady charge for most of it's discharge period.
Discharge Rate
What is also known as C rating is the battery's discharge rate which is measured in amps. The discharge rate is the maximum current that a battery pack can discharge at without causing any damage to itself. Battery packs with a higher C rating will be able to handle higher discharging rates than those with a lower C rating. A higher C rating also means a heavier battery. This is where you need to make a compromise between the two – weight and flight time.
Battery Capacity
The battery capacity is measured in mAh which stands for milli amp hours. This rating shows how many milli maps can the battery provide the drone with per hour. Battery capacity can also give you the time which a drone can stay airborne for. You can find this out by multiplying the battery capacity with it's amp draw (C-rating) and then dividing that result with 1000. For example if you get a battery with 1500 mAh capacity the supply of power (draw) will be 1.5 A which when multiplied gives you 2,250. By dividing this number with 1000 you get 2,25 which is the number of hours and minutes the drone is going to stay airborne for with a fully charged battery.
Connectors
In order for the battery to work with your drone it needs to have the correct connectors. There are different types of connectors which also allow you to use the same battery with a different drone. The most common battery connectors are XT60, EC3 and Deans/ Tplugs. Make sure to check the connectors on your drone before purchasing a battery pack.
Voltage
A battery's voltage is the energy difference between it's negative and positive terminals. The higher the voltage of a battery pack the more power it can provide the drone with without increasing the current or amp draw. This means the battery can provide longer flight times.
Getting the Most Out of a Drone Battery
Charging
Knowing when to charge the battery is a crucial part of extending its lifespan. One should never leave the battery to charge longer than a couple of hours before using it. You should also charge drone batteries every other day to keep them working at their best. Rechargeable batteries are known to discharge even when they are not in use so make sure to charge them on the regular even when you are not using the drone. Otherwise the drone battery will discharge completely which can cause damage to the cells and affect the battery's capacity.
Camera
If your drone is able to shoot video then you might want to consider taking off the camera when you are not going to be filming. This will not only reduce the weight of the drone but also reduce the amount of power the battery needs to provide for the drone to stay airborne. The camera itself uses battery power even when you are not using it as the viewfinder is active.
Conditions
Using the drone in stressful weather conditions will put a lot of that stress on the battery too. The drone will drain the battery faster as it will be harder for it to move or stay in place. This will result in shorter flight times and less fun times too.