Help with electric setup for newbie to electric

[Tim Donald]

Can anybody help me with a Pilot Laser 67" setup please? I'm coming from glow engines so electric is new to me.

My plan is to run the standard Pilot-RC CC20/400KV Motor with Hobbywing Platinum 100A ESC and 4x MacGregor MG5921HV High Voltage Digital Servos. I was going to use a 6s 5000 Lipo and Futaba R3008SB receiver (HV).

The ESC spec has a 8.4v output. Can I simply plug my servos into the receiver and power it all from the 8.4v output on the ESC? Is this the best way to do things or will I need a powerbox of some sorts (I know nothing about them). Anything else I have missed?

Thanks.

[Allan Bennett]

That ESC appears to have a big enough BEC (battery eliminator circuit -- it eliminates the need for an Rx battery) to cope with the servos you've mentioned. So just plug it into the throttle channel of your receiver and it will provide power for the receiver and attached servos. You say your Rx and servos are HV, but just check that that means they can take 8.4v. If not, the ESC can be programmed to give a lower Rx voltage I believe.

One risk of using the BEC that's built into the ESC is in the unlikely event of the ESC failing catastrophically, it might cause the BEC to fail. If you're paranoid about this, or you think the servos' current demand may be more than the ESC's BEC can handle, you can either run the Rx from a regular Rx battery pack, or use an external stand-alone BEC. In either of those cases you would need to disable the ESC's BEC by pulling its red wire from the plug, so that you don't get two different Rx power sources competing with each other.

One thing about electric flight that you may not be familiar with is the need to pick the right prop. The motor will try to turn at (Kv x voltage) rpm irrespective of what prop size is on it. If the prop is too big, requiring more power than the motor can deliver, the motor will still try until it burns itself out. A wattmeter is an indespensible tool which will tell you how many amps, watts, and volts are being used, and with it you can check that the recommended prop size is okay and, if not, try a larger (to get maximum power) or smaller (to avoid overload) oner.

[Tim Donald]

Allan, Thank you ! That is a fantastic reply that answers all of my questions perfectly. I want to keep the weight down so I think I will stick with the BEC on the ESC and hope it doesn't fail.

Interesting point you make about the prop. I hadn't really thought about that. Anyway - I have bought a recommended power pack that includes the prop so hopefully it is the correct size but that is good to know for future projects.

Thanks again - if we ever meet I owe you a beer or two !

[MattyB]

If you are worried about a BEC failure you could always fit a backup power supply unit and monitor when it kicks in via telemetry; the Optipower Ultraguard is a great little unit and only weighs 40g.

Edited By MattyB on 04/10/2020 20:33:15

[MattyB]

Tbh having just looked at the model and the servos recommended I would be inclined to just fit a 2S lipo or life pack and be done with it. Being for 20cc petrol engines and weighs 3.6kg it’s not going to notice the additional mass of the RX pack, and I’m sure it will still be significantly lighter than the petrol version.

[Tim Donald]

Thanks MattyB. Lots of options !