Can any tell me if there would be a problem with connecting the 4 x ESC directly to the APM outputs 1 - 4 rather than going via the Power Distro board?

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I'm doing this at the moment. I didn't leave enough clearance on my custom frame to plug the ESC servo leads onto my distro board. Plugging them directly into the APM also provides it with +5v. Everything works fine.
But: cut 3 out of the 4 red +5V cables from the ESC to the APM!
Why do I need to cut 3 out of 4 red +5V cables?
Mine works fine without cutting any of the red cables.
I've heard that the issue with not cutting 3 of the 4 wires is that you have all 4 ESCs trying to maintain about 5v of power...but each ESC will try and maintain a voltage that's slightly different from the others so there's some thought that they will compete.

Hi, Christopher!

As Randy said, is not recommended to use BEC from all ESCs at same time.
If you want to use BEC from ESCs, you need to take it from just one of them.
You don't need to cut the middle wire (+5V) from the cable.

Here goes how I did it:


By that way, you can just put it back, if you need to use the ESC in other project or so. ;)
Take care to not bend the cable too much.

Really?  Can you pls explain the consequence of this?

 

I'm going to be assembling a hexa, and I plan on using to Power Distro boards, with the ESCs connected to to the APM.

 

Thanks

Hello Hai, it wasn't tested on lab, but the theory could help us to bring up a thesis:

What happens when you join two batteries in parallel and one of them have less charge than other? The less charged will drain the current from the other one, until both achieve the same potential. In mean time, the more charged will be forced to give away more current, up to the "equilibrium point" between them.

Well, you can expect something like it occurring with the ESCs, with a big difference at the "balancing" part... that will never happen. Firstly, they are not perfect and will present different output values. So, theoretically, when joining it, you should have some leakage current drained between them and it means unnecessary power lost and some noise added. Furthermore, the system will never balance, because they are not batteries. The ESC with higher output value could be overcharged and get hot beyond the expected where supplying energy to APM all by itself. You can try to solve it by adding a diode on each line just to make sure the drain will not occur by different potential between them (maybe they have it internally... but I don't know). Or, --the easy and cheap way-- attaching just one.

The best way ever is not feed APM from ESCs. Instead, you can add an external BEC, so each ESC will not get hot beyond the expected when just driving the respective motor. That's how I did on mine.

I hope it could help you to understand better the problem and why we not recommend joining the ESCs BEC on APM power rail.

Thanks very much for the explanation. very helpful.

Thanks for explaining that, makes perfect sense. I should probably disconnect three of the +5v lines now! 

there is another they where you don't need to change anything on the connectors...

 

turn the connectors upside down and connect only the signal pin, the two other pins not connected -> everything works (i have it working like that on my quad)

Sebastian, yes that is one way to do it but then you would ground signal line trough main battery - cable and that might cause unwanted noise to your electronics. Always when you have signal line and shield/gnd along with it, you should connect them both and now leave one up in "air" as an reflector.

 

This might work for you for someone else it might cause crashing.

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