Whether you're building your own drone or flying one that you've purchased online, you will need to understand LiPo batteries to some degree. Likewise, you will want to understand LiPo battery monitors so that you can utilize them to keep your batteries fresh and your drone safe. It is entirely possible to encounter alternative battery technologies, such as NiCad, but this is rare on more modern drones.
Your LiPo battery is the main power source of everything your drone can accomplish. It powers the motors, lights, electronics, cameras, and anything else you have attached. LiPo stands for Lithium Polymer, which is the chemical technology used to store energy inside the battery. The LiPo technology allows for an above-average energy density in comparison to older battery chemical like Nickel Cadmium.
As you might have guessed, a higher energy density means that it can store more energy than a battery that is the same weight and size, but with a lower density. It basically translates into a higher capacity for the same weight. And weight is important when you are dealing with drones and other forms of remote control aircraft.
The increased density is the reason why these batteries have phased out the older technologies like NiCad. It's entirely possible to get the same voltage and capacity with a NiCD battery, but the weight would be much higher, which would hinder the flight ability of the drone.
A simple LiPo battery is built from a combination of cells. A single cell is made from metal and some chemicals that can generate a small electrical charge. The cells are then connected, either in series or in parallel, to increase the capacity or the voltage of the battery itself. When two cells are connected in a series it causes the voltage to increase and when two cells are connected in parallel it causes the capacity to increase.
If you're ever searching to buy LiPo batteries or a LiPo battery monitor you will run into various terms, numbers, and abbreviations that you may not understand. Once you know what the numbers, letters, and words mean you can easily decipher the potential of the battery or monitor and determine if it suits the needs of your drone. It's very important that you understand how the batteries are notated in their descriptions.
The first component of any battery that you must consider is its cells. Some information on cells was discussed previously. You could consider a single cell by itself to be a battery; however, a battery typically refers to two or more cells.
Every LiPo cell has the exact same nominal voltage. That voltage is 3.6 Volts. When you connect two cells in a series to create a standard battery, then those voltages are added together to create a 7.2 V battery. You will learn later that the voltage of the battery can actually decrease at times, which is one of the main reasons you use a LiPo battery monitor.
LiPo batteries are often described in terms like “2S” or “4S2P”. The “S” stands for series and the “P” stands for parallel. “2S” means there are two cells in a series, thus the voltage of the battery is 7.2 V. “4S2P” means there are 4 cells in a series and then 2 parallel sets of such a series, which makes for 8 cells in total. When two sets are connected in parallel they must always have the same number of cells in a series.
There are three big factors that you look for when purchasing a LiPo battery for a drone. These factors will affect the ability of the drone to fly and the amount of time it can spend in the air. These factors are:
The voltage has already been mentioned. Its importance is that the voltage must be high enough to create a suitable current for the motors. The nominal voltage of a cell is 3.6 V and the safest maximum voltage is 4.2V. As you use your battery, the voltage will drop. Some motors will stop functioning if this voltage drops too low.
A LiPo battery monitor is used to keep an eye on the voltage of the battery while in flight. If the battery voltage drops to a dangerous level, then an alarm will signal that it's time to land the drone and charge the batteries.
The capacity of the battery is determined by the number of parallel sets. It is referred to as mAH, which stands for milliamp hours. Simply put, the higher the mAH the longer the drone can fly. However, increasing parallel sets to increase the capacity also increases the weight of the battery significantly. It's a careful tradeoff.
The final factor to consider is the discharge rate of the battery. This is usually labeled as the C rating. The C rating is used to determine how fast energy can be pulled from the battery. The C rating of the battery must be able to keep up with the draw of the motors in the drone. If the C rating is too low then the motors could damage or completely destroy the battery. If you were mid-flight, then this would be seriously bad news.
Once you have purchased a battery for your drone you must be sure to properly store, charge, and monitor the battery. A battery monitor is a very simple, yet helpful tool. It works like a voltmeter, but usually has additional functions, such as a low-voltage alarm.
The quality of the lipo battery charger makes a big difference as well. The charger must cut-off before pushing the battery above the maximum safe voltage of 4.2 Volts.
Likewise, you want to charge the battery at a safe and slow speed of 1C. There are some chargers that can push much higher speeds up to 5C. This will charge the battery faster, but it also shortens the lifespan of the battery and decreases their stability. If properly cared for and monitored, a quality LiPo battery can last for a very long time.