Hi Atreius Models, Good to hear you have isolated one of the power leads. If your ESC has an on off switch it should still be used as I have damaged an Mtronik Esc in a multi-prop model by failing to switch on both ESC's. I use three on my Olympic and have a panel with the three switches side by side so I can easily see all are on or off.
dave976

Hi Rodc give me a small while, the drawing is not to hand at the moment, when I find it I will copy it to you.
I used a circuit published in the now defunct Model Cars, an off-shoot of Model Maker magazine.
But BEC's are so cheap now I would not bother to make my own any more.
Regards
Roy

In my experience, forget about using two Mtroniks esc’s together even if a red wire is removed from one of them. I even used an Mtroniks optical isolator to eliminate stray cross current interference. To no avail; both of them failed just north of immediately. Mtroniks tech folks were extremely helpful trying to resolve the issue but finally said they could not figure out a solution. Mtroniks esc’s are superior when used singly but I will never again try them in tandem.
Just describing what I faced with the twin installation in my avatar boat.😔

Thank you very much everyone for your help, I'll remove the red (+ve) cable from the 10A ESC as this seems to be the simplest option given both ESCs have a built in BEC.

@RNinMunich I currently have 2, Bizmork and a smaller but similarly themed one named Gork's Revenge. You can find photos of both on the linked Facebook page. I plan to upload photos of Gork's Revenge here when I find the time to modify/rebuild her.
It was my first 'proper' attempt at building a model boat and I've learned a great deal since building her and want to go back and redo the internals including as big a motor as I can squeeze in for towing.

Roycv a schematic wud be more explicit. You cud draw it black on white paper, then photograph it & attach it to your post. Despite all my electronics experience i cant envision what you just said.
Best regards, Rod

BEC Battery Eliminator Circuit. I used to make my own. Just a small power transistor and a Zener diode a couple of resistors and a plug to go into Rx.
The Zener diode is 0.7 volts below the required voltage. A battery the other end, could be the drive battery. All mounted on a small veroboard maybe a LED to show it was working.
With this circuit as the voltage decreases it does not switch off suddenly
Roy

Photos please 😜 and what is a BEC?

I agree with RNinMunich - only one power source to your ESC, but rather than chop the wire off, just disconnect it at the plug and tape it back. In that way it can be used again if ever needed. To disconnect you just need to use a needle to depress the sprung tang, then carefully withdraw the wire from the plug. 😉

When modifying the leads for extra (multiple) ESCs (battery eliminator circuit) I usually take only a small amount of the red wire out, somewhere not too close to the connector or ESC. Gap needs to be only a few MM. Then insulate the cut (electrical tape...). This way you can re-use the ESC by re-connecting the wire.
Lew
Florida, USA

A Missive from Atreius Models ...
(You have been warned😁)
Nice one Ben👍
Any ship/boat models in your collection?
😎
https://www.facebook.com/AtreiusModels/

Sorry TD, I guess I kinda took that as read!😔

😎

What Doug said... except I tape off the red wires. One never knows what the future might bring....😊

Hi AM,
To cut to the chase ...
Golden rule is ONLY ONE power source for the receiver, whether from a BEC or a separate battery ONLY ONE. Otherwise you risk potential damage 🔥 to either the receiver or one (or more) of the BECs/ESCs.
So choose the strongest of the BECs and chop 😮🙈 the red wires of the rest.
Happy sailing👍
Cheers, Doug😎

PS: It is not important if the ESC's use separate batteries. What matters is that they are electronically controlled by the same receiver, which can tolerate only one BEC connected to it.

Whenever running more than one ESC THAT IS EQUIPPED WITH BEC's, the red lead in the servo lead from the ESC should be removed. This ensures that only one BEC feeds the required current to the receiver.
My current build uses five ESC's, all equipped with BEC's, but because of the current requirements for the # of servos each receiver drives, I am using stand alone BEC's. Therefore the red lead on all of the ESC servo leads is removed. Hope that is not too confusing.😀