A small receiver for parkflyers with a capacitor that gets charged by the battery pack and holds enough charge to power the servos for 30 seconds to a minute in case your pack gets ejected or the esc fries. It would be like having a receiver pack but without the added weight.

Doable? Practical? Or does it already exist?

a ParkBEC would work if your ESC fries ($17) but wouldn't help if you eject your battery- Just don't eject your battery and you'll be just fine.

Jim

Good advice but it doesn't tell me if I have invented the next great thing or just had a dumb idea.

I can't imagine there is a big calling for a device to protect against ejecting batteries. The CG issues would probably keep many from landing in one piece anyway. And the burnt up speed controller part as I said could be handled by a ParkBEC if somebody is concerned enough to want to protect against it.

Party pooper. I was going to cut you in for half the profits but now... you're out.

Originally Posted by BrunswickOH

. The CG issues would probably keep many from landing in one piece anyway. .

Have you never landed a model with the pack dangling by its leads? The CG is way out of wack but it still controllable.

difference between dangling and OUT OF PLANE

If you really wanted to do this, here's what I'd do.

I can make you a 4.2v ParkBEC. Power your RX from that. Also, take a very small single cell Lipo and add a servo connector. Plug that into a spare channel like you would an RX pack. I'd suggest a Kokam 145. In operation, the parkBEC would keep the Lipo charged, and the lipo would power the servos in the event of a battery ejection. The whole setup would weigh about 11 grams and cost under thirty bucks.

Good idea, Mex!

Originally Posted by Comatose

If you really wanted to do this, here's what I'd do.

I can make you a 4.2v ParkBEC. Power your RX from that. Also, take a very small single cell Lipo and add a servo connector. Plug that into a spare channel like you would an RX pack. I'd suggest a Kokam 145. In operation, the parkBEC would keep the Lipo charged, and the lipo would power the servos in the event of a battery ejection. The whole setup would weigh about 11 grams and cost under thirty bucks.

Thanks but that defeats the whole idea of coming up with a brainstorm. I don't want to add a UBEC or a seperate receiver pack. I thought I came up with a good idea. Obviously NOT.

Alternatively one could make a lipo cell that had charge circuitry built in which would run from 5v to keep the single lipo cell charged, and then have a diode or other circuitry to allow the cell to provide power in the event of a power failure. That'd be pretty doable too, but significantly less off-the-shelf than a 4.2v ParkBEC.

Either way what you suggest is both possible and plausible. I'm not sure how often batteries are violently ejected (not often for me, YMMV), but I could see it being saleable as a general purpose safety device in case of any power failure.

*edit*
But you already are adding a separate reciever pack, its just a capacitor instead of a battery. A cap that can power servos for any length of time is going to be heavier and more expensive than carrying around a truly tiny RX pack which wither way would charge from the onboard power just like a cap would. I can see the value of building that into an RX for sure, I just don't make RXes and wouldn't want to have to buy another one to add the feature.

OK, ok. I get it. You are not big fans of my idea,

Actually I liked it. If you think of the little lipo cell as a capacitor, then I'd even consider putting it into production. The problem with a normal capacitor is it just doesn't have enough juice. If you say that "normal" servo current is about 100ma, then the big cap on a castle P25 would give you about 5 milliseconds of servo power. So to do it with a real capacitor would take a quite large cap. Like, five Farads large. For reference, that would be five thousand of the largest capacitor on my desk in parallel.

there was a case posted of a plane ejecting its battery while set for high throttle... and the windmilling prop had the (brushed) motor acting as a generator... allowing a controlled landing. (fortunately he didn't have a major CG change...)

But.. it really is best to just be CERTAIN the battery can't eject.

If you want a backup power supply.. try a flexible solar cell.

Originally Posted by Comatose

Actually I liked it. If you think of the little lipo cell as a capacitor, then I'd even consider putting it into production. The problem with a normal capacitor is it just doesn't have enough juice. If you say that "normal" servo current is about 100ma, then the big cap on a castle P25 would give you about 5 milliseconds of servo power. So to do it with a real capacitor would take a quite large cap. Like, five Farads large. For reference, that would be five thousand of the largest capacitor on my desk in parallel.

Then how about a tiny watch or camera battery?