When you build a mini quadcopter, there are many questions you will meet. For example, how to choose the lipo batteries? What’s the different between 3S lipo battery and 4S lipo battery? How to choose the motors?…I have knew more about lipo battery, and today I will talk about the different between 3S and 4S lipo battery.
First you must know what is 3S lipo battery? what is 4S lipo battery? I have one article is about these, and now I will have a simple description. When you bought a Gens Ace 1300mAh 3S 25C lipo battery, the “3S” is the voltage of this lipo battery; as we know, 1S=1 cell= 3.7V, so 3s=3cell= 11.1V. So 4S lipo battery is a 11.1V lipo. I advise you can read this article:The analysis of lipo battery parameters to know more about lipo battery knowledge.
The next step is talking about the different between 3S and 4S lipo for mini quadcopter. It’s kind of obvious, the main difference is voltage that powers the motors. In my experience with cobra motors, the speed of my quad goes up a lot because of the extra 1S.
Let’s say we have a 2300KV motor, when powered under 3S lipo (12.6V), RPM (rotation per minute) is 2300 x 12.6 = 28900 (in theory). That means the motor spins 28,900 times a minute with no load. When you power the same motor with 4S lipo (16.4V), the RPM is 2300 x 16.4 = 37720, a huge increase in RPM.
Increase in RPM means more thrust, more power, and your quadcopter flies faster. However, the relationship of motor thrust and voltage is not linear due to efficiency loss. Some motors perform well in 3S, but not as good as expected in 4S where most energy just transforms into heat. Apart from thrust, we also need to consider other aspects such as torque, current draw etc. The easiest way to determine if your motor is suitable for 4S is to search for thrust data table, or test it yourself. Some motors rated for 3S simply cannot run on 4S, where the high voltage/current could damage and burn the wires.
Some might ask if a 3S quadcopter can out perform a 4S quad, the answer is definitely yes. Many factors come into play that can determine the speed of a quadcopter: combination of motors and propellers, weight, etc. But under the same condition, a multirotor that runs on higher cell count battery should have more power thus faster.
Also note that 4S setup are usually a little heavier than 3S, because of the additional weight of the voltage regulator, and heavier batteries. Like many high capacity batteries are all heavier than low capacity batteries. So you can accord your need to choose the voltage of your battery. If you want to build a racing quadcopter, I advise you can bought a 4S lipo with high discharge, like Tattu 1300mAh 4s 75C lipo battery.