LiPo batteries (lithium + polymer) are rechargeable batteries which are commonly used in radio-control electric systems: aircrafts, helicopters… and drones.

LiPo batteries (lithium + polymer) are rechargeable batteries which are commonly used in radio-control electric systems: aircrafts, helicopters… and drones.
 
They are usually made up of several identical cells arranged in series in order to get higher voltage, and in parallel to increase the discharge current capacity. The setting up is: lithium metal anode, a copolymer made of polyethylene, vanadium oxide and lithium salt (LiTFSI).
 
Three features made them the perfect kind of battery for radio-control flights:

• They are lightweight and can be manufactured in almost every shape and size.
• They have high capacity, and therefore can reach high levels of energy in a reduced size.
• Its high discharge rate allows to feed the most demanding electric systems.

The more serial cells, the higher the voltage can be. The nominal voltage of one cell (1S) is 3.7v, and the most usual battery settings would be:

• For toy mini multicopters:
  • 1S – 3.7v
  • 2S – 7.4v

• Small and racing multicopters
  • 3S – 11.1v
  • 4S – 14.8v

• Professional medium-sized multicopters
  • 3S – 11.1v
  • 4S – 14.8v

• Professional large-sized multicopters
  • 5S – 18.5v
  • 6S – 22.2v
  • 7S – 25.9v
  • 8S – 29.6v

On the other hand, depending on the size of the cells, we can increase the power they can store, being the most usual ranges:

• For toy mini multicopters:
  • 80mAh – 750mAhv

• Small and racing multicopters
  • 1000mAh – 2500mAh

• Professional medium-sized multicopters
  • 3000mAh – 16000mAh

• Professional large-sized multicopters
  • 8000mAh – 32000mAh

How to choose our LiPo battery?

When choosing the most appropriate LiPo battery for us, we should consider four factors:

Battery size:

the ideal solution would be to choose the battery with the higher storage capacity, but it is not always possible due to the device features. Therefore, before purchasing the battery, we suggest to quantify the UAV’s maximum take-off weight, and to carefully measure the physical space in which the battery will be placed.

Technical features:

capacity, download speed and number of cells are the three crucial parameters that we should consider when estimating the flying time supplied by a given LiPo battery. In order to know if the battery we have chosen is enough battery for our drone, we will calculate the maximum discharge ampere of the battery and the maximum consumption of the drone, and we will check that the battery capacity is higher than the drone consumption.

Practical example of calculation for a suitable battery:

First we will calculate the maximum current the battery can give.

Battery details:

• 6 Cells
• 22.2V
• 222.0Wh
• 10,000mAh
• 25C

Calculation

10,000mAh * 25C = 250,000 mA maximum -> 250A maximum

Then we will calculate the maximum consumption of our drone

Drone details:

• 8 motors
• Maximum consumption per motor: 21.2A
• Safety factor 40%

Calculation

8 motors * 21.2A * 1.4 safety factor = 237.44A

Finally we compare the consumption of the drone with the electrical capacity of the battery

• If the power consumption is higher than the battery current -> inadequate battery
• If the consumption is lower than the battery current -> suitable battery

250A maximum in the battery > at 234.44A in the drone consumption, this battery would be suitable for our drone

Battery connector:

in order to choose a connector, we must consider the current flow it must support, and naturally, your own connection preferences. In this case, the safest bet is probably to choose the most popular connectors in the market, which are (from smallest to biggest):

Number of batteries:

The pros and cons of installing more than one LiPo battery in a drone must be kept in mind. Using several batteries connected in parallel is safer, as if one fails, the others will keep on providing energy. However, using several batteries makes the assembly more complex, and more expensive as well.
 
All of these are only AIRK advices. But of course, the final choice is in your hands!