Electronic Speed Controllers

Deciphering the Specifications

Another common cause of confusion when shopping for an ESC is the specifications. There's quite a few, and the information presented to you can get quite complex. So let's run through the important things, and help you understand what they mean for the ESC you're looking at.

Battery Eliminator Circuit (BEC)

A BEC allow you to run the receiver off of your battery pack as opposed to using a separate battery pack just for the receiver. When looking at this, the most important thing to remember is that 6-volts instead of a 5-volts will provide more power to your steering servo. This will make them turn quicker and have more torque to turn bigger tires with.

Drive Frequency

An ESC controls the motor by switching itself on and off thousands of times a second. The more times an ESC does this in a second, the smoother your throttle response will be. However as the throttle response goes up the efficiency goes down. While an ultra-high frequency rating may be beneficial for touring cars, it's not necessary for an off-road truck. Anything from 500 to 2000 Hz should work fine for an off-road truck. Anything lower than 500 Hz may give you some noticeable roughness at low speeds.

Forward Current

Often people mistakenly think this number has to do with how much power the ESC sends to the motor. They think the higher the forward current, the more powerful the ESC. That's incorrect, it's a measurement of the rate at which the ESC can supply the electricity. In theory this number is relative to the turn limit of the ESC. However the measurement of this figure varies widely between manufacturers. So it would make more sense to heed the motor limit itself.

Motor Limit

This is probably the most important specification of an ESC. The less turns a motor has the more current it will draw, and the ESC has to be capable of doing this. The motor limit is determined by efficiency and on-resistance. You not going to be able to take an ESC with a 17+ limit and run a 13-turn motor on it for very long.

You will also want to know the limit of your ESC when gearing your motor. If you are using a motor at the ESC's specified limit, you'll need to be extra careful not to over gear the motor. Even an ESC rated for 13+ turns, can be damaged by over gearing a 13 or 14 turn motor.

On Resistance

This is a measurement of how much resistance there is when the ESC is used. The lower the resistance, the less drop in voltage there is from the battery pack to the motor. So a lower on resistance translates to more power, less heat, and more efficiency.

Reversing vs. Forward Only

A reversing ESC is just what it sounds like. It gives you the capability of running in reverse as well as running forward. A forward-only ESC will only allow you to run forward. I often see someone picking an ESC with excellent specifications, but it's a forward only ESC. If you're going to be primarily bashing around the house, and not competing in races at the local track, you should strongly consider a reversing ESC. The advantages of having reverse to back out of a jam, become readily apparent after you have to run over to the truck a few times and do it yourself.

It is not legal at most tracks to run an ESC with reverse. However you can get the best of both worlds with some ESC's, as they are reversing, but they also allow you to disable reverse. This allows you to have reverse when bashing, but also let's you also use the ESC at your local track. If racing is the primary purpose of your truck, then you may want to consider a high-end forward only ESC, as they often have better specs. than even the best reversing ESC's do.

Wire Size

The larger the wire size running from ESC to battery, and ESC to motor, the more efficient it will be. There are a multitude of ESC's on the market running 16 gauge wire. For a 13+ turn ESC, I would recommend looking for an ESC with at least 14 gauge wire, with 12 gauge being even better. An ESC with a rating of 11+ or lower, should really have 12 gauge wire.

Part One:	Introduction to the ESC
Part Two:	How an ESC Works
Part Three:	Deciphering the Specifications
Part Four:	Recommended ESC's
Part Five:	ESC Comparison