BEC hook up

[Frank Skilbeck]

Looking at fitting a standalone BEC to a 3m electric glider, ESC is opto type, and remove the separate Rx battery. Glider has 6 servos, 2x aileron, 2 x airbrakes, elevator and rudder.

 

Thinking about connecting the BEC to the flightbattery (4s) balance lead connector, as this will allow model setup/adjustments without a live motor, is this a bad idea?

Edited February 10, 2023 by Frank Skilbeck

[Dickw]

I thought about doing that with a 4.7m electric glider I have just put together, but did wonder about the current carrying capacity/reliability of the balance lead connector. After thinking about it for a while I decide that if I needed to think about it that much it might not be the best idea after all.

 

In the end I went with a conventional arrangement of connecting the BEC to the ESC battery input. With such a big model I also decided to go with a separate Rx battery for redundancy which also allows me the ability to set up the model without a live motor, so I do understand where you are coming from with your idea.

 

Dick

[Chris Walby]

I thought it was a good idea once.

• Martin suggested it was not a good idea, IIRC he may have had some issues or knew someone who had
• I have actually experienced really unreliable connections (wondered why the RX would power on and off) depending on which battery I used and if the cables were flexed

Its really disappointing as the connectors have a good power rating, but I guess the design is not really for the stresses and flex of flight. OK if its connected and used on a charger, but of course its a less critical application and unlikely to suffer vibration/flex of the cables.

[Neil R]

I've done this once before, on a 2 x 3s Extra Slim Twin (7 servos), and it worked fine. (In my case with a BEC equipped ESCs, but with the red wires removed, and so with a separate stand-alone UBEC. It just made the wiring routes easier). If you've chosen an opto because you wanted true isolation, I do wonder if you are compromising this? But for me, on other models, I've used optos purely because I always knew I wanted the reliability offered by a separate UBEC. And then have powered said UBECs 'worry-free' from the main flight battery anyhow. I have also used balance leads to supply power to sound systems.  Obviously in all cases taking power from the outer wires of the balance lead (to avoid cell imbalance), and make sure you are happy regarding the physical security of the new connectors.

[Allan Bennett]

Ever since I switched to 2.4GHz I've been using stand-alone BECs in place of the Rx batteries that I used with my opto ESCs.  They're all connected directly to the ESC's battery plug.  Never a problem in 20 years or so.

[Frank Skilbeck]

Thanks for the comments, it's not actually my glider but a club mates, he keeps turning up at the field with lipos charged and a flat Rx battery, as he forgets to charge this!

 

The only reason it's an opto ESC is that is what came with it.

 

I think it's probably safest to solder the BEC to the ESC main battery plug rather than worry about the balance lead.

[RottenRow]

You could still fit a battery isolator in the lead between the ESC connector and the ESC itself if you wanted to power the radio with the motor remaining dead.

 

Brian.

[Allan Bennett]

A switch is a potential failure point, so better in my view to plug in the old NiMh pack if testing without the motor is required.  Or simply remove the prop.