Why is Your brushless motor getting Hot (Solved!)

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RC motors, especially the brushless ones, are one of the most vulnerable mechanical components of the RC car. 

They get hot because the electric energy used to run them transforms into heat.
According to the second law of thermodynamics, whenever energy is being used, some of it becomes waste heat.
In fact, you need to ensure that your brushless motor stays at a maximum temperature of 170°F to prevent the motor from overheating and damage. 

When it involves a hot brushless motor and how to keep them within the best working temperatures, there are several things you need to know. In this article, we learn about the brushless motor to better understand how and why the brushless motor overheats and what you can do to prevent it.

What causes a brushless motor to heat?

Several factors can make your RC motor heat up. In most cases, the cause could be a single fault or a combination of multiple problems. 

Regardless,  the four most common reasons your RC brushless motor is getting hot include the weather condition, terrain, how you use it, and the setup. 

  1. The Operating Conditions

The climate condition is the first reason why your RC brushless motor will overheat if not set up correctly. There’s always a big chance that your brushless motor will heat during the hot summers due to the high temperatures. But, just because summers are pretty hot and winters are cool does not mean your RC brushless motor won’t heat up in the cold. Your brushless motor will also overheat when you drive for extended hours in the cold climate. 

  1. The Terrain or load

Where you race or bash your RC car will also determine how hot the brushless motor can get. 

Newton’s third law states that For every action, there is an equal and opposite reaction, that what make your RC car go, but also gets your motor hot. The resistance of the surface causing the motor to work harder, under heavier load, and that will also determine how hot your brushless motor will get.
Each terrain comes with its amount of strain on the motor so for example, asphalt and paved roads won’t strain your brushless motor as much as a surface with dirt and tall grasses. 

  1. The Setup and gearing

The setup of your RC vehicle also causes your brushless motor to heat.
If your brushless motor is geared too high or too low, the motor is not running under optimal load and gets hotter.

  1. The Usage

As the name suggests, how long you run the brushless motor determines its temperature levels.
The longer you use your RC vehicle, the hotter it will get. 

Read More: All The Causes Of A Burned Brushless Motor

Are brushless motors supposed to get hot?

It depends on the type of motor you use. 

When you use smaller brushless motors, they usually won’t overheat. However, the larger you go through, the hotter your brushless motor will run. Most motors can take the heat without much problem. But some even get to the point where it burns instantly to the touch after using it for some minutes. If that’s the case with your brushless system, check your gear meshing to ensure you have no binding anywhere. Also, avoid straining the motor. 

In short, some brushless systems aren’t strong enough for some uses. If you use them on something it wasn’t intended to do, it will get hot.

How hot should a brushless motor run?

Technically, an RC brushless motor can run at a temperature up to 150°F (65°C). Temperatures between 150°F and 170°F are also safe, depending on the quality of your brushless system and how well it can hold heat. However, you need to avoid raising the temperature over 170°F (76°C) because doing so might weaken the rotor’s magnets. 

The effect of heat on your magnet is that it loses its magnetic power, which means increased KV ratings and high heat output. The goodness is that some RC brushless motors are designed with thermal overload protection, which helps you shut down the motor when it passes its temperature limits.

Can a brushless motor overheat?

Sure, a brushless motor can overheat. Nothing will happen to your brushless system if the temperature is relatively minor. If it heats up badly, several things can go wrong, from the permanent magnet losing its magnetic power to winding failure to the bearing, which will cause your RC to fail.

What the heat of the motor has to do with efficiency

Heat and electricity are forms of energy and the more efficient the motor, the less it gets hot. The electricity that is not being used, or getting wasted, transforms into heat. When an electric motor gets hot, it means that some of the energy is wasted in the form of heat.
A 100% efficient motor will not get hot as all of the electric energy is being consumed by the motor, transforms into movement, and none of it is ‘going out’ of the system. The less efficient the motor, the hotter it gets since some of the energy transforms into heat and gets wasted.

So, if your brushless motor Is getting too hot, or getting hotter than before, it can mean that there is a problem or a fault with the motor, and it’s worth inspecting it before it gets too hot and burns. 

All brushless motors get hot

The only time brushless motors won’t get hot is when you tune them properly. They also won’t get hot if they stay within the temperature and gearing limits stated in the owner’s manual. Some brushless motors will get hot to 130°F and some to 170°F.
However, some RC car brands that use high-quality materials to design their brushless system will perform better even at 180°F range. 

Do brushless motors need cooling?

A brushless motor overheats because of poor tuning and setup. Luckily, you easily prevent them from overheating when you apply cooling effects. 

You could either add a cooling fan or heat sink to lower the RC motor temperature by 10° to 20°F.

The only situation heatsink may not be applicable is if the brushless system (for some reason) has ventilation holes on its sides rather than the tops or bottoms. When you install a heatsink in this situation, it covers these ventilation holes, which would make things worse.

Get the best information: Do RC motor heat sinks actually work (do you need one?)

Conclusion

Heat is a common issue associated with RC motors, whether brushless or brushed. For the brushless system, it can do more harm than good, from damaging the rotor’s magnet to the winding of your RC car. So, if you notice that the temperature hits over 170°F (76°C), you need to learn to use the RC car without putting so much load on the motor.