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-   -   Peak amp draw durring start (http://www.rcuniverse.com/forum/rc-jets-120/11236052-peak-amp-draw-durring-start.html)

flyinfool1 09-21-2012 12:15 PM

Peak amp draw durring start
Has anyone measured the peak amp draw during the start / flight / shutdown of a kerostart turbine.
I am betting that the peak current will be during start-up, just before the kero plug shuts off.
Everyone always says its a lot, but has anyone ever actually measured it to know for sure what it is?
I tried, but my Amp meter only goes up to 10A and it is more than that on a kero start P70.
I am not after the total Amp hours used in a flight, just the instantaneous peak current.

I would be interested in the differences between different turbine, sizes and brands.

I am building a plane that I am watching every gram that goes into it, I intend to fly with a small pack and use a bigger pack for start and shutdown power.

David J Ruskin 09-21-2012 12:18 PM

RE: Peak amp draw durring start
HI, Yes i use Multiplex telemetry on ECU current draw. With my Jetcat 120SX kerostart the ECU draws 26 amps to start, then runs at 1.5 to 1.7 amps.


kelly vallee 09-21-2012 01:47 PM

RE: Peak amp draw durring start
What are you using for a battery? Lipo, A123, Life or what?

David J Ruskin 09-22-2012 12:47 AM

RE: Peak amp draw durring start
For the Jetcat 120 SX I use a 5200 2S LiPo. Each start takes about 350 milli amps, so I can safely fly all day without the grunt of recharging. Rx batts are 2X2200 2S LiPos.


miniman 09-22-2012 01:19 AM

RE: Peak amp draw durring start
We have a kerostart P120 and that draws around 25-30 amps peak during start. My friends Gas start P160 only pulls 2amp peak during start. I have never tested he draw with he motor running but an educated guess bassed on total usage during a flight is that its milliamps rather than Amps.

Our P120 uses around 500Ma per flight including the Start and cool down process.


flyinfool1 09-22-2012 10:43 AM

RE: Peak amp draw durring start
So then I should be safe using ~800mAh 2S LiPo for running and can then plug in my big 5,000 mAh 2S LiPo into a Y harness for start up and shut down on a MW44 gold Kero start.

I don't care if I have to charge often. I would rather be light to fly better.

Me thinks me has a plan starting to come together.......

ww2birds 09-22-2012 12:55 PM

RE: Peak amp draw durring start
Sounds like a good plan FF1. I've seen several folks at jet flyins doing just that with a booster battery for start on kero systems. Funny that the booster batt approach still leaves you with an extra piece of flight-line gear (the booster vs the propane can) .. I'd say 90+% of folks just use larger batts onboard, but for a 44-size plan this would be a great tradeoff.


Henke Torphammar 09-22-2012 01:13 PM

RE: Peak amp draw durring start

ORIGINAL: flyinfool1

Has anyone measured the peak amp draw during the start / flight / shutdown of a kerostart turbine.
Yeap!! A kingtech K170 seem to have a 35watt(5.5amps on a 2S pack) burner and uses 100mAh for one start :-)

I see no point in registering the peak as a stalled our speed 300 starter uses maybe 50A "peak" but that's only a tiny bit of time.

flyinfool1 09-22-2012 02:09 PM

RE: Peak amp draw durring start
True the peak is for a very short time, but the system must be able to handle that short peak, no matter how high it is.

At least on my P70 the starter motor is ramped up slowly so that you do not get the big stalled rotor peak from the motor. The big amp draw is the Kero burner. I just did not know how much.

That is my plan for now, If I need weight for CG I usually add it in the form of bigger batteries. I hate useless weight........[>:]

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