Also referred to as ESC for short, electronic speed controllers is the device that is in charge of controlling the speed of the motors.

 

If you’re interested in how a speed controller works, take a look at the article posted below.

https://www.elprocus.com/electronic-speed-control-esc-working-applications/

 

 

Generally for ESC’s:

 

One side of it will have one black and one red wire. You will connect that either in a circuit with the battery or to an electronic speed controller.  The red is the power wire and the black is the ground. On this side you will also find the signal wire which will usually have female headers attached. The white/yellow wire is for the signal, the black is ground, and the red is plus 5 volts.  

The plus 5v wire is for powering other electronics through the battery eliminating circuit (BEC) that comes with some ESCs. There are other forms of BECs such as the linear BEC or the UBEC which stands for universal battery eliminating circuit. Based of my research, any good ESC will come with one but you do not want to use the plus 5v wire. It could overload the ESC and which will lead to really fowl smelling smoke. On the other side you will find either three sockets in which you solder wires into or you will find wires already pre-attached. These wires will have to be connected to the three motor wires. You generally want to solder bullet connectors so you can easily switch the wires or change the ESC if needed. 

 

Current. Each ESC will have a max current rating. You generally want to get the 30A ESC. They will also recommend which battery to use with it.  Some might also have low voltage cutoffs and high temperature cut-offs. They are not necessary to have however it is up to you if you want them or not. Just remember that if a cut-off is triggered, a crash is bound to happen.