What is Electronic Speed Controller

Electronic Speed Control terms

On resistance:

This is a measurement of how much resistance the ESC has against the flow of electricity when the transistors inside the ESC are turned on. Lower on-resistance is better because that mean a smaller voltage drop, which in turn leads to less heat, greater current capacity, and higher efficiency.

Forward current:

This is the rate at which the ESC is able to supply electricity. Forward current is limited by the ESC's thermal and electrical efficiency. Different manufacturers have different ways of measuring this number so it is pointless to compare "forward current" published by different manufacturers. Some manufacturers quote different maximum and continuous forward current figures, which is a bit more helpful. But even then, the usefulness of those numbers depends on the definition of "continuous". As a rule of thumb, use the forward current rating only as a reference. Pay more attention to the manufacturer's recommended motor limit.

Drive Frequency:

Lower drive frequency is more efficient, but higher drive frequency results in a smoother throttle response. A frequency between 1000Hz to 4000Hz is good for most situations. On road cars tend to benefit more from higher frequencies, while off-road cars or cars raced on tight tracks do better with lower frequencies. I've never seen anyone benefit from a frequency beyond 4000Hz at a club level race. There still are some ESCs operating with the old 60Hz frequency. These ESCs are noticeably rough at low speeds, which is okay for off-road trucks, but to be avoided for on-road cars.

BEC

When an ESC is used, its Battery Elimination Circuit takes some of the electricity from the battery pack and use it to power the receiver and servos. This is why the on/off switch is on the ESC, and not the receiver. Generally, it is preferred to have a 6-volt BEC circuit with at least one ampere of current capacity. Many of the high-end ESCs offer as much as 5 amperes of current. Higher current allows more powerful ESCs to be used. However, some ESCs come with a 5-volt BEC circuit. While 5 volts are enough to operate a radio system, it is better to have 6 volts because the servos turn quicker and have more torque.

Wire Size

Generally, 12-gauge or lower is used for high end racing ESCs. 14-gauge wire is sometimes also used, but it is more commonly used in mid-end ESCs. 16-gauge wire is good for back yard bashing and stock class racing.