Single 2s Lipo for turbine and RX for Jetcat P20
 

Hello,
I am going to be moving my P20 with a V 10.0 ECU to a hand launch delta, so I am looking at minimizing weight as much as possible.
I am considering using just one 2s Lipo to power both the turbine and RX (using high voltage servos I.e. no BEC. My receiver is rated to handle a 2s Lipo).

I seem to remember reading that this should never be done because of potential noise generated from the pump that could cause interference with the RX. Is this the main reason? It would seem that current high power EDFs using a BEC equipped ESC are more likely to generate so much more noise yet they seem to work fine.

I understand about battery redundancy, but again, a BEC equipped electric airplane has only one battery that feeds the motor and RX.

I look forward to any comments and suggestions.

Thanks.

Mr.G

I use a similar set-up on my Savex L-39/ Wren 44. I have a Jeti Li-Ion 5200mAh pack that runs the radio, engine, retracts and brakes. I can get at least 10 flights before needing to recharge. I use a BEC for the radio though as I have standard voltage servos. Going HV would eliminate that need.

A perfect solution for a small model.

Paul

I run 5700 mah 2S Lipo on the turbine. When my V10 ECU sees a low voltage, it fails to start the turbine. That happens typically after about 6 or maybe 7 starts and flights. When it fails to start, the start cycle gets about half way thru ker.full mode and shuts down. When I put in a fresh battery, it starts. If you can get a start, power-wise you should be good to go. Once you get past the start, turbines appear to be using little mah.

On my system, a failure to start happens after ~ half the mah of the power source is used up. At that point, there is still plenty of voltage and mah there to run a Rxer and servos. However, I always use two separate batteries for a Rxer. In the past, I have put a scope on gas planes and seen various spikes on the power system's CDI circuits. I have never scoped a turbine to see what it generates. I just assumed RF was potentially there and separate the power systems.

Guess whether or not you use one battery for all power depends on how much you want to risk the plane and turbine. Given that I am typically stuck adding weight to get a good CG, I don't mind that weight being the second and third battery for a Rxer. Your situation appears to be a lot different. So maybe the weight savings is worth the risk.

Of course, you could scope the power circuits and look for the RF, ... just to be sure. Might take a UHF scope or Station Monitor to see everything that could potentially impact the Rxer. But if you do not see symptoms of stray RF on the ground, you probably will not see them in the air either, at least until the voltage drops. But then, I suspect that the typical failure to start would preclude that situation.

Just my thoughts! Personally my SOP is if I can afford to take the risk, I try typically try. Then once I get the 5 test flights in, I figure I should be good to go even where there are other people around.

Thanks very much Paul and Len for the feedback. Looks like this option is not as uncommon as I thought.
Best Regards,
Ghislain

I was reading the description of HH's small 8 cc gas plane. It is a bit contrary to what they have published in the past about their Rxers. Apparently, they run the entire plane off one battery. They either have the ignition figured out to preclude RF or the Rxers are not subject to RF. I just noticed this after reading your post!