What does the extra drone capacitor do?
The additional drone capacitor functions as an electronic filter. In general, a filter is configured to remove unwanted aspects from a particular signal. They are mostly configured to suppress specific ranges of unwanted signals, such as high frequency motor vibration noise or electronic noise in the form of voltage instability. For this instance, the capacitor is installed to smooth out voltage noise created by the battery.
Speaking of batteries, capacitors function similar to batteries. The capacitor stores energy in the form of an electrostatic field between its internal plates instead of storing energy chemically. Its job is to smooth out or electronically filter noise.
Adding capacitor at the source of the power protects the entire system by preventing the introduction of unwanted noise. However, the flight controllers have software filters which are used to filter other noises in the form of vibration. See our detailed explanation how flight controllers work!
What is noise and how do you minimize it?
There are numerous components that can produce noise. If you still have a noisy quad and you’ve tuned the PID loops, checked the props, tightened all of the screws, put rubber dampeners on the flight controller mounting, etc… etc… then there is a good chance the source of the noise could be coming from your battery.
We’ve identified some common symptoms that can potentially be cured simply by adding a capacitor:
- Noisy video feed is a sign of electrical noise in the power
- Listen to the motors and see if there are oscillations that you can’t tune out with PID
- Check for hot motors
- ESC and motors fall out of sync – Noise can corrupt your ESC signals and motors
- TX/RX radio signal weak or erratic
Follow the link below for additional information on other methods to filter noise using BetaFlight’s Dynamic Filter feature.
How do you know if you should attach a capacitor?
We strongly recommend that even if you don’t have a noisy build, it’s a good preventative forethought to add a capacitor, anyway. It might even save your electronics from being damaged by voltage spikes.
Which type and size drone capacitor to buy?
We recommend low Equivalent Series Resistance (ESR) capacitors for FPV Flight. Capacitors with lower value ESR exhibit much better filtering capabilities. Why? This is what determines how sharp a spike the capacitor can absorb, and it needs to be a low as possible. The voltage needs to be rated for the highest voltage spike it’s likely to encounter. We recommend at least 50V for FPV Flight, but It’s certainly a trade-off between smoothing and size. A 1000uF capacitor is cheap and readily available.
Where to Connect the additional Capacitor?
It’s very important to know the polarity of each leg of the capacitor. If you make a mistake soldering the capacitor it won’t work or it can even explode! Understand which leg is positive (+) and which is negative (-). The shorter leg indicates negative, if you cannot see the negative label on the body. We trim the legs of the capacitors as short as possible for a cleaner build.
There are 3 places where you can add capacitors for them to be effective. You only need to install them in one of the following locations:
- (Most Common) Solder the capacitor on the Power Distribution Board (PDB) where XT60 pigtail is soldered. Make sure the (+) lead of the pigtail is soldered to the (+) side of the XT60 connector.
- Solder the capacitor where the ESC power leads are also soldered to the PDB.
- Solder the capacitor on the power terminals of each ESC.
- Solder the capacitor to any of the vbat pins.