How to choose a lipo battery for FPV
The FPV racing drone is powered by a LiPo battery, mainly because the LiPo battery can store and deliver a lot of power. There are several factors to consider when choosing the right battery for you.
- The size of the battery
The first thing to consider is the physical size of the battery, because depending on the drone you are using, the location of the battery is limited and you need to install a battery of a certain size. So when buying a battery, first look at the size parameters given by the manufacturer(the follow picture). Often the size of the battery is related to the battery capacity and voltage.
- Battery capacity and discharge rate
The capacity of the LiPo battery is measured in mAh . mAh basically means the current that you can extract from the battery for one hour.
For example, for a 1000 mAh Lipo, it takes an hour to fully discharge if a constant 1A current is drawn from it. If the current draw is doubled to 2A, the duration will be halved to 0.5 hours. If you keep pumping 30A, this battery pack can only last for 2 minutes. Increasing battery capacity may increase flight time. In general, it is best to get the highest possible capacity battery. Higher capacity can also provide you with higher discharge current, but the weight will be larger and larger, physical size. The bigger. There is a trade-off between capacity and weight, which affects flight time and aircraft flexibility.
In addition, another factor to consider is the discharge rate. Using a too low discharge rate (C rating) may cause damage to the battery, and the drone's battery is not enough to quickly discharge current to properly power the motor. Since the higher Class C battery is heavier, if you use a battery with a C rating that is too high, you will carry the extra weight , which ultimately reduces flight time.
How to calculate the maximum continuous current output of the battery
To know the total current consumption of your drone system, we calculate it based on this simple formula:
For example, for a 1000mAh 6s 100C LiPo battery . To find the largest continuous current, we first convert 1000mAh to 1Ah, then multiply that number by 100C to get the total continuous output 1 x 100 = 100A
Since the maximum current output of the battery depends on the capacity and C rating, there is no need to use a fixed C rating. Generally, the smaller the battery capacity, the higher the C rating.
- FPV battery connector
The battery connector should match the battery connector you are using on the drone. In fact, most FPV battery connectors are use the XT60 connector. This allows you to easily replace the battery, and if you decide to make another drone in the future, you can use the same battery.
In addition, Lipo batteries are equipped with 2 sets of wires/connectors: balanced leads and main leads or discharge leads (except for 1S batteries, only main leads). As the follow picture:
- Battery voltage
LiPo cells exist in the battery, and each LiPo cell has a nominal voltage of 3.7V (of course, some high voltage batteries have a nominal voltage of 4.2V). The LiPo battery is designed for a safe voltage range of 3V to 4.2V. Discharges below 3V may result in irreversible performance loss or even damage to the battery. Overcharging above 4.2V can be dangerous and eventually lead to fire.However, for battery health reasons, it is recommended to stop the discharge when it reaches 3.5V
.If a higher voltage is required, these cells can be connected in series to form a single battery. We usually don't mean the battery voltage, but how many cells, or how many "S", in the battery.
For example, a 11.1V battery is referred to as a "3-cell" or "3S" battery.
It's another important decision you need to make. Higher voltage batteries can make your motor produce more power, but higher voltage batteries are heavier because they contain more cells.
The voltage directly affects the RPM of the brushless motor, so if your motor/ESC and other power supplies support higher voltages, you can use more cells to increase the speed of the quadcopter. The way to find the optimal voltage for the drone in terms of battery voltage is to look at the motor thrust data sheet and compare the efficiencies. You will find that motors are generally more efficient and powerful when using more cells (higher voltages), but the increase in weight and cost of the battery offsets some efficiency gains. Therefore, depending on the number of motors you use, you need to choose the motor that best suits your current setup.
One thing to remember is to make sure your motor/ESC and other electronics support the battery voltage. Some motors only support a specific cell count, or a specific voltage range, which may make decisions easier.
- Number of batteries
The number of batteries you decide to use on your drone is not much different, because using more batteries has its advantages and disadvantages. First use more batteries with an extra layer of security, as if one battery should fail, and you have another battery that can be used to land quickly. Also, if you have the flexibility to replace one battery, if one of the batteries is older than the other. If you have two chargers, you can reduce the charging time because each charger can be charged at the same time. However, using two batteries may be more complicated to install and wire.Therefore, the final use of one or more batteries can be attributed to the drone you are using and your own preferences.