LiPo Battery Basics

Lithium polymer batteries, more commonly known as LiPo battery , have high energy density, high discharge rate and light weight which make them a great candidate for RC applications.

By learning the basics about LiPo batteries, you will be able to read and understand their specifications.

Battery Voltage and Cell Count (S)

LiPo batteries used in RC are made up of individual cells connected in series so the battery’s voltage is the sum of the voltage of the cells. Each cell in a standard LiPo battery has a nominal voltage of 3.7V. Therefore battery voltage is often referred to as how many cells in the battery (aka “S”).

1S = 1 cell = 3.7V

2S = 2 cells = 7.4V

3S = 3 cells = 11.1V

4S = 4 cells = 14.8V

5S = 5 cells = 18.5V

6S = 6 cells = 22.2V

For example, we call a 14.8V battery a “4-cell” or “4S” battery.

Voltage affects brushless motors RPM directly, therefore you could use higher cell count batteries to increase your quadcopter’s speed if your motor/ESC and other electronics support higher voltage. But a battery with more cells of the same capacity is heavier since it contains more cells.

A LiPo battery is designed to operate within a safe voltage range, from 3V to 4.2V.

Discharging below 3V could cause irreversible performance lost and even damage to the battery.

Over-charging above 4.2V could be dangerous and eventually cause fire.

However it’s advisable to stop discharging when it reaches 3.5V for battery health reasons. For example for a 3S Lipo, the max voltage is 12.6V, and you should land when the voltage reaches 10.5V (at 3.5V per cell).

LiPo Battery Capacity and Size

The capacity of a LiPo battery is measured in mAh (milli-amp hours). “mAh” is basically an indication of how much current you can draw from the battery for an hour until it’s empty.

For example, for a 1300 mAh Lipo, it would take an hour to be completely discharged if you draw a constant 1.3A current from it. If the current draw doubles at 2.6A, the duration would be halved (1.3/2.6=0.5). If you draw 39A of current non-stop, this pack would only last 2 minutes (1.3/39=1/30 of an hour).

Increasing  your battery capacity might give you longer flight time, but it will also get heavier in weight and larger in physical size. There is a trade-off between capacity and weight, that affects flight time and agility of the aircraft.

Higher capacity could also give you higher discharge current as you will see in the next section.

Fello Tech Co., Ltd. established in 2005, is specialized in the research and manufacturer of lithium polymer battery, li-ion battery, LiFePO4 battery and primary lithium batteries. It occupies more than 30000 squares feet of floor space and employs more than 1000 skillful workers in production team with more than 40 experienced engineers and technician and becomes one of the most innovative lithium batteries manufacturer in the industry.