Anybody any idea how you know what speed controller to put with what engine / battery, is there a general rule of thumb and also what difference they make ie will an 18 amp speed controller make a plane go faster or slower than say a 30 amp speed controller ???
Cheers,
Neville

The speed controller itself doesn't determine how fast or powerful the plane will be.

Rather it merely supplies the current needed by the motor and prop combo.

If the ESC is too small for the prop/motor, you'll burn it out quickly.

There is no set rule of thumb for all of this.

You basically make choices based upon how you want your plane to fly and the resources you want to expend.


There are many on-line calculators that help you with your configuration.

Google for "RC Prop calculator" and "RC Power" calculator...

Electrifly has a nice on-line interactive configuration guide as well but only for their hardware.

Remember to use the manufacturer's ALL UP FLYING WEIGHT multiplied by an additional 15-20% to get your actual flying weight.

actually, a lot of companies have gotten better about that.

Anyway, back on topic, yeah, the rating of the speed controller just has to be big enough to not fry, other than that, it's the least important issue with putting together an electric system. The only reasons not to put in way over-rated controllers is price and weight.

Estimate power required based on the motor and battery, then pick a controller to match. If the motor is rated at 20 amps, anything bigger than that is good, anything less is risky.

Even though the motor is often more expensive than the controller, if the motor fails, you glide in for a landing. If the controller fails, if it's a BEC-equiped system, you may crash. Even if it's not a BEC system, it's still connected to the radio system, and could cause a loss of radio control on failure.