what capacitor capacity do you recommend at the power input to the PDB in the configuration 12S (44,4V), using 6× T-Motor Alpha 60A ESCs, with ESC wiring around 50 cm each and battery leads around 20 cm.
For example in documentation about SmartAP PDB Installation | SKY-DRONES DOCS , it is recommend using a ~100 µF capacitor for setups above 8S. I understand this is mainly for high-frequency filtering, but in case where the system includes relatively long wires and high current loads (35A in hover) also?
Could you please advise whether I should follow this recommendation as-is, or if it would be beneficial to use a larger capacitor bank (e.g., 1000–3000 µF) to better stabilize the DC bus in this type of setup?
The critical things with those capacitors is the voltage, you want up to double the normal operating voltage. 63v caps would just be OK, 80v would be better but harder to get. This is why a lot of those larger ESCs have two capacitors - they will be in series to double to voltage but this halves the capacity. The high voltage rating is needed because the ESCs generate high voltages when braking the motors.
The capacity (microfarads) is less critical, basically as much as you can get in the available space. The capacitors should be as close to the ESCs as physically possible.
Capacitors should be the Low ESR type, and keep the leads VERY short.
So if you connect two 50v 470uf caps in series you’ll have 100v 235uF.
A good sized cap or two on the power distribution board doesnt hurt either.
The best layout is ESCs mounted inboard close to the power distribution and battery connector(s), and long phase wires to the motors.
Phase wires can be as long as you like without detriment - power wires cannot.
63v minimum, 80v OK, 100v best, capacity as much as you can afford. After capacitor is charged 63v one will have less empty capacity left than 80v, so it can absorb smaller spike.
No spark connectors like XT90-S is must.
Unfortunately, I can’t install capacitors on the voltage input to the ESCs because I’m using a T-motor integrated propulsion system, and I hope the manufacturer has taken care to install the capacitors in the housing. Therefore, the ESC power cables from the PDB are approximately 50 cm long on each arm. The only place I can install a capacitor is on the voltage input to the PDB.
not clear which ESC / Motorsystem you are really using. First you write ESC T-Motor Alpha 60A which is not an integrated propulision system as you now write.
This small capacitor at the input of the PDB is not helpfull, but also it is not disturbing. On the input of the PDB you already have a large Capacitor called 12S battery. A filter on this point doesn’t help on all issues behind this input. So as @xfacta said the only real helpfull placement is as short as possible to each ESC.
I thought it didn’t matter, because the integrated propulsion system I use: 605-X Professional Aerial Photograph Drone Propulsion Kit
has a build-in Alpha 60A ESC, but in an integrated housing with two visible capacitors inside.
Hi Pawel, that’s ok. Can ou show a good picture of these capacitors as on the T-Motor page I can’t identify. On the other hand if this product is for professional use it will be ok as it it.
So just to follow the SmartAP recommendation your selection is OK
Unfortunately, I can’t take a photo to read the parameters of these capacitors, only their top is visible, and the housing has screws glued with strong thread glue.
I think there is something similar to the FLAME 60A 12S ESC, i.e. 2x in series 63v 330uF capacitors:
The T-Motor integrated motors with Alpha ESC also have the same capacitors → 63v 330uF in series. I’ve got a couple pulled apart - you dont want to know why they’re pulled apart
