How Does RC Car Work? A Complete Guide to RC Car Electronics

So you just got your first RC car and you’re itching to take it for a spin. As you grip the controller in your hands, you can’t help but wonder – how do these things actually work?

In this complete guide, we’ll give you a comprehensive breakdown of all the electronic components inside a hobby-grade RC vehicle, explaining exactly how they function and work together to make your car zoom across the pavement.

Whether you’re a total newbie or a seasoned RC enthusiast looking to brush up on the fundamentals, read on to get the full scoop on RC car electronics.

The Battery – The Powerhouse of your RC Car

The battery is essentially the “fuel tank” that stores and provides all the necessary electrical energy to make your RC car move.

There are two critical specifications you need to be aware of when it comes to RC batteries:

Voltage

Expressed in volts (V), voltage determines how fast the electronics and motors in your RC will operate. More voltage enables the motor to spin faster.

However, there are limits – feed a component too much voltage and things will fry out immediately. Smoke coming out = not good!

So you’ll want to make sure your battery’s voltage matches the ratings of the electronics in your vehicle.

Capacity

Measured in milliamp hours (mAh), capacity determines how long your battery will last before it needs recharging. The higher the mAh, the longer the run time.

A 5000mAh battery that has a 5 amp draw placed on it should theoretically last 5000/5 = 1000 minutes = 16 hours before being fully depleted.

In the real world the run times are much less due to system inefficiencies, but higher mAh generally equals longer runs either way.

So when you see two identical vehicles with the same battery getting vastly different run times, capacity is usually the reason.

Okay, electronics 101 lesson over! Now we can get into the fun stuff…

The ESC (Electronic Speed Controller)

The battery gets plugged into the ESC, which controls how much of the battery’s power gets sent to the motor.

It regulates the motor’s speed by adjusting the amount of current flowed. At full throttle, maximum amps flows from the battery to the motor via the ESC.

Many modern ESC’s are fully programmable, allowing you to tweak settings like acceleration curves, braking strength, drag brake forces and more.

But ultimately, its job is simple – more power to motor = more speed!

Brushless Motor KV Rating

Brushless motors have a KV rating, which specifies the number of RPM it spins per volt supplied.

So if a motor has a KV rating of 3000KV given 8.4 volts, the calculation is:

8.4 volts x 3000KV = 25,200 RPM!

That’s over 400 revolutions per second at full power!

More KV generally equals more speed, but there are always tradeoffs with low-end torque, efficiency, and longevity to consider.

With brushless systems, you want the KV matched with the gearing and battery voltage for optimal efficiency.

Brushed Motor Turns

Brushed motors idsntify power and speed by the number of “turns” or windings of copper wire inside. Lower turns equals faster speeds.

As a general guideline:

• Buggies – 20-25 turns
• Monster trucks/short course – 25-30 turns
• Crawlers – 35+ turns

Too low and you’ll just burn up the motor. Too high and you won’t have enough speed for the power system to be fun.

Electronic Speed Controller (ESC) Features

We briefly covered the ESC earlier as the device regulating power delivery to the motor. But modern ESC’s also have a few other helpful functions:

• BEC – Battery Elimination Circuit: The BEC is an internal circuit that takes the main battery voltage and lowers it to 6V to power the radio receiver and steering servo. This allows them to be powered separately from the motor system.
• Variable BEC Voltage: Some ESC’s let you adjust BEC output voltage. So if running high-voltage electronics, you can increase BEC output accordingly.
• Motor Rotation Control: Sensorless brushless ESC’s can reverse motor direction by swapping two of the three power wires. Helpful if the motor spins the wrong way after rebuilding or swapping parts.

Okay, so the ESC takes the battery power and feeds the motor as well as the receiver/servo. But how do the radio controls actually work? Keep reading!

The Radio Receiver

Your controller’s signals are sent via radio frequencies to the receiver, which relays the commands to the ESC and servo accordingly.

This allows you to wirelessly control throttle and steering from a distance.

The receiver requires only a small amount of current to operate, which it draws from the ESC’s BEC circuit mentioned earlier.

The Steering Servo

The receiver takes your steering commands and passes them to the servo, which then moves the front wheels accordingly.

The amount of force a servo can apply is expressed in kg/cm or oz/in.

For example, a “20kg” servo can provide 20 kg of force on a 1 cm arm from the output shaft.

Higher quality servos have metal gears and stronger motors to resist stripping under heavy loads.

The servo connects to the receiver’s signal line to receive input, and the receiver’s power lines to get operating current.

Some extremely powerful servos can overwhelm the BEC circuit though, in which case an external BEC is required. More on that next.

External BEC

As mentioned earlier, some high power servos need more current than a typical ESC’s BEC can provide.

When this happens, you’ll experience “glitching” or stuttering/jittery behavior as voltage momentarily drops. AKA the dreaded “brownout”.

An external BEC solves this by taking raw battery power as input, then stepping it down to 6V (or user adjustable) for output to high-demand electronics.

This provides a clean and stable supply of current that won’t brownout.

2-Channel Radio Communication

Most RC cars utilize a simple 2-channel radio system. One channel controls the steering servo, the other controls the ESC/throttle.

When you turn or accelerate, pulses of varying widths are transmitted from the controller and decoded by the receiver.

More advanced models may add a third channel to control features like lights or other accessories.

The ESC and servo wires typically have one positive (red), one negative (black) for power, and a third “signal” line (usually white) where the pulse commands from the receiver are received.

Proportional Electronic Controls

Unlike old school on/off switches, all hobby-grade RC controllers provide proportional control.

This means the steering and throttle operate gradually and incrementally based on how much you press each trigger or turn the wheel.

Gentle trigger pull = gentle acceleration. Aggressive cranking of the wheel = aggressive steering angle.

This proportional control gives you much finer adjustment over steering and speed.

So when you nail an epic drift around the cul-de-sac, you can rightfully claim your superior driving skills are 100% responsible!

…Just don’t forget to also take credit for the subsequent tree crash too.

Putting it All Together

In summary, here is the full flow of components and signals in a typical RC car:

• Battery installed in car
• Battery connected to ESC
• ESC sends regulated power to motor (controls speed)
• ESC also sends reduced 6V BEC power to receiver
• Receiver sends BEC power to steering servo
• Controller transmitter sends steering/throttle signals to receiver
• Receiver relays signals to servo and ESC
• Servo moves steering linkage according to steering signals
• ESC adjusts power to motor according to throttle signals

And that in a nutshell is how all the electronics in your RC car work together to make it zoom around!

Of course, every vehicle and model is a little different in capability, programming, and exact electronics used. But hopefully this guide gave you a good general overview of how the main components communicate and function.

Let’s wrap this up…

Final Thoughts

Phew, that was a lot to digest! But congratulations – you now know more about the internal electronic systems of an RC vehicle than 99% of casual hobbyists!

Understanding these fundamentals will help you maintain, modify, and upgrade your rides for better performance and functionality.

While advanced electronic wizardry has made modern RC’s incredibly capable, it’s still important not to overlook the basics.

So if you ever lift the body off your car and stare confused at the spaghetti wire mess underneath, refer to this guide to get reoriented with what’s what!

Have fun out there and drive safe!