When to Use a CapPack in Your Air or Surface Setup

- The full article was originally published on Castle -

What is a CapPack?

A CapPack or Capacitor pack is a bank of capacitors that are electrically wired together to form what we would know as a pack. It can be useful in brushless motor applications where it serves to give just that little boost needed to overcome ripples in the battery voltage caused by hard acceleration or long battery wires.

Ripple voltage is extremely hard on an ESC – adding the CapPack can help reduce the load on the controller’s on-board capacitors. The result would be prolonged lifespan of your ESC.

In general, ripple voltages should always be less than 10% of the total pack voltage, and the smaller the ripple voltage the better. If an application exhibits more than 10% ripple voltage, you should consider using higher discharge (C Rating) batteries, shorter wires, higher current connectors, better gearing or a smaller load.

What Setups Would Benefit from a CapPack?

Helis: CC CapPack is highly recommended for all 500 class and smaller heli applications where Y harnesses and long wires can bleed voltage, and hard collective pulls can strain even the most powerful batteries.

Surface Vehicles: With their high torque requirements – going from 0 to 100% throttle isn’t easy on controllers or batteries – RC cars and trucks put enormous loads on brushless power systems. Use CC CapPacks in high performance applications (IE drag racing and high speed runs) to help your system power through the abuse.

Fixed Wing Aircraft: Larger electric power systems lead to larger electric powered aircraft, and sometimes the distance between the battery pack and the ESC grows beyond the length of the wires installed on the components. Adding wire also adds inductance, which can increase the ripple voltage in a system. CC CapPack essentially negates the ripple caused by the addition of up to 12 inches of length to the battery wires.

Quick Facts About CapPacks

• Multiple CapPacks may be used in an application.

• CapPacks should be installed as close to the ESC as possible.

• CapPacks will add capacitance to a setup and will therefore increase the snap that occurs on plug-in.

• Installation of CapPack(s) in a brushless setup will not make a poor setup into a good setup, nor will it (they) compensate for batteries that are unable to deliver the amps demanded by the load. The CapPack product is intended solely to compensate for minor voltage loss across long wires.

• A cap pack does not add any additional voltage to the system because caps are charged by the system battery, so they only charge to the batteries’ voltage level. They do help support the battery so that it performs better, however it only helps out while the voltage is. If you have an incredibly good battery, you may not even need a cap pack because it won’t have enough voltage sag the cause ripple voltage.

How do I Know What CapPack to Purchase?

Honestly though, there is no magic equation for picking the right cap pack because every setup is a little different. Ripple voltage is largely dependent upon the quality of your batteries.

The better your batteries, the less ripple voltage you will have and the less capacitance you will need to fight your ripple voltage. You could have two exact same setups but with different quality batteries and the one with the better batteries will have lower ripple voltage.

Therefore that setup will need less capacitance than one with lower quality or less healthy batteries. The best thing to do is to look at your data logs and make the assessment based upon the level of ripple you are seeing in the real world.

Castle offers three CC CapPacks, one is rated for up to 12s and two (with different units of electrical capacitance)that are rated up to 8s.