Why use a Cap Pack on an RC Car? (Capacitor Pack)

A look at a cap pack.

A Capacitor pack is a fancy name for a bank of capacitors. That is a bunch of capacitors that are electrically wired together to form what we would know as a pack. Each capacitor is wired in parallel to each other. The idea is to place the cap pack as close as possible to the ESC on the battery to ESC wires. The purpose is to smooth out any voltage dips that occur during operation.

What a Cap Pack will NOT help / Capacitor Boost

You may have heard that a Capacitor bank helps with the performance of a Radio Controlled vehicle. This is one area that we will need to set straight right away. Capacitor Boost, ya, not really a thing. Cap packs are not installed to increase the top speed of our RC car. They will also not help to increase the acceleration we can achieve out of our car. Essentially, cap packs do not store nearly enough energy in order to discharge this to the motor increasing power potential. In fact they would not store enough energy to operate the Radio Controlled vehicle for even a split second. For this reason we should not expect any improvements to RC car performance.

Purpose of a Cap Pack (Capacitor Pack)

When an ESC is powering a brushless motor, the ESC must turn on and off power to each of the motors winding’s. The main purpose of a capacitor is to fill the void in voltage as the ESC is switching the motor on and off. An example of where the voltage void comes from would be when the battery is under load. As the battery is under load, the voltage tends to drop creating a voltage drop that could be read across the ESC. As the ESC turns a winding in the motor off, the battery unloads and causes a potential dip and spike in voltage. It is possible during this spike that the voltage can be higher than the source voltage. The capacitor bank is able to fill in the void in order to maintain a more constant or steady voltage across the ESC power input. Now let’s look at which RC car can most benefit from more capacitors!

Does my RC Car need a Capacitor Pack

RC Cars that pull a lot of power and are pushed very hard for short duration’s of time tend to be the offenders that are hard on ESC’s. It doesn’t matter if your ESC is rated for 200A and you are only using 100A of that current handling capacity. What is critical is as we noted above, the cyclic voltage drop that occurs across the input side of an ESC. Using a Cap pack in these high demand applications can only help your ESC by reducing the variance in voltage.

Examples of a few RC Car applications that would benefit the use of a cap pack include:

  • RC Drag Car
  • RC Speed Car (Car specifically designed and raced for achieving highest maximum speed)
  • A vehicle that has been geared for a high rate of speed similar to above

What Cap Bank do I Require? (Capacitor Pack)

There is no magic solution as to the exact specifications you require in your application. What we do know, is that a Cap pack, will not harm your RC vehicle in anyway other than to simply occupy space physically. Therefore, it is recommended to choose a Cap pack that has a minimum of 800μF.

When running your RC Car, keep an eye on the temperature that the capacitors are reaching. Higher temperatures indicate that the capacitors are being taxed more significantly. The cooler the temperatures are, the better off your components will be. The result would be prolonged lifespan of your ESC.

To look at the installation details of a Cap pack, visit the Cap Pack installation part of the extending ESC wires page.

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