A343

My Feedback: (4)

Elec. power consumption during start-up, is so big that there isn't enough to spin starter motor to max during starting seq./heat element lit. Only 2.600 - 3.000rpm achived, during second start-up . Which makes start a little slower and hotter. (first start w/ "fresh" batteries gives 4-5000rpm)
FlightPower Lipo 7.4V 4350mAh + Std. JC Lipo 2500mAh tested, battery leads to ECU is thicker than the JC leads ECU-to-Eng. ECU v6.0Q (just upgraded due unable to get enough voltage at all to starter motor + heating element), two different heating elements tested (one of them works great on my P120SE)

Anyone conv. a P-180 to kero with good results?
Regards
Thomas

KC36330

add a Y harness to the ECU and use a booser pack during starts.

A343

My Feedback: (4)

Thanks for the tip. Allready tried it, with both mentiond batteries. No improvement, unfortunately. What teases me is the GSU batt. indicator. It's only "full" when voltage is close to 8V. With 7.7V only 3/4 full.

KC36330

do you have it set to the right cell count??

A343

My Feedback: (4)

I belive so. 2 cell Lipo 7.4V in Turbine limits menu and in the menu where start pump voltage is adjusted it says NiCd K-cells:6. Acc. to JC Germany this is correct?

KC36330

6 cell is correct for a 2s LiPo

mr_matt

My Feedback: (10)

That is correct.

The P-180 and P-200 use the same starter, and with kero they are going to need maybe 25 or more amps. In the cold, this can be a very demanding requirement. Too many connectors, weak solder joints, weak cells, etc all can take their toll. Make sure the kero ignitor is fully primed (the fuel head should be right up to the ignitor).

I will talk to JetCat to see if they have any tips. I would be running a NiCad or lo impedance NiMh or even LiFe to make absolutely sure the instantaneous current is OK. I know that JetCat sells that LiPo, I am just saying what I would try personally.

Regards,

A343

My Feedback: (4)

Thanks for your advise Matt.
I'm presently in NYC, so I called Bob yesterday to get his opinion. The eng. is actually bought here in the US last year.
I'll be back at home tomorrow to do some more testing in the coming days. I'd consider the NiCd alternative and maybe changing the leads inbetween ECU and Eng.
Thomas

mr_matt

My Feedback: (10)

I have a P-180 with a pretty long ECU battery lead (maybe 3 feet?) with a connector inline. I had to add an extra cell to a very high quality (low impedance) NiCd to overcome the I^2R losses in the cable.

And that P-180 is on gas start.

Regards,

A343

My Feedback: (4)

Thanks for your input Matt.
We'll do some extensive testing tomorrow, measuring voltage drops and current flow with different batteries and wires.
I've a feeling that the wires might be undersized, the wires from the ECU-to-Eng. gets warm by only spinning the starter motor at 5000rpm.
A pure guess, as I haven't cut the mentioned wires, is that their area is maximum AWG 15 i.e. 1.45mm2. Starter motor is pulling 6-8Amp, the heating element + the fuel pump? We'll find out tomorrow but we're talking about in excess of 30 amp, at least momentarily. We'll find out tomorrow.

Acc. to the table in link below, a AWG15 wire can take a maximum of 28amp

http://www.powerstream.com/Wire_Size.htm

Thomas

A343

My Feedback: (4)

Ok, test session is over.

Highest current drain during start up is not more than 16amp. Heating element peaks at 10amp, starter motor at 8amp, but start up sequence makes no item run at peak value at the same time.

Voltage drop with std JetCat 34" wire from ECU to Eng. is significant; 0.9V during start up (max load)! (Measured at ECU Bat plug and Eng. socket)
I changed this 3wire bundle to AWG13/2,5mm2 wires, now voltage drop is only 0.3V!
In my SM F16 1/6, the battery wire is 29" long btw Bat and ECU, voltage drop is 0.3V (AWG11/4mm2). So with the new installation, a total drop of only 0.6V iso. 1.2V w. the JC wire.

It seems I have a LiPo pack problem since it should be able to maintain its nominal voltage of 7.4V during this relatively low load, compare to its capacity (20C 4350mAh). And it is not, FlightPower UK has confirmed it should be able to do this easily.

My conclusion: Starter motor (bigger in P180+P200) together with Kerosin start in a P180, puts a heavy load on supplied std wires. With the voltage drop, we're getting close to "LowBat" warning in just a few starts, if battery is not up to maintaining its voltage. Battery capacity is not a problem, start up consumption to idle is approx 3-400mAh.

I'll go for the thicker wires in the future for this engine.
Thomas

A343

My Feedback: (4)

Last test session is over.
With the AWG13 wire harness between ECU-Eng. I've tried two Battery packs with success!

A 7-cell SANYO Cadnica 1700mAh NiCd (recieved endorsement from JC Germany that this is ok) and
a 7.4V 2S1P KOKAM SLPB 3600mAh 30C LiPo

6 consecutive startups were made with 30s idle then shutdown, followed by a cooling cycle to <70degC then immediate new start. OAT and fuel temp was +4degC(39F). All startups were successful with a small hesitation in the last startup with the NiCd pack.
Current consumption for the NiCd test was 1400mAh and the LiPo 1457mAh, so they are comparable.
Size, light weight, availability and proved performance of this KOKAM LiPo pack (#8643128H5) makes my choice easy in the future.

Thomas

mr_matt

My Feedback: (10)

Very nice work, Thomas!

Thanks very much for sharing the information! I will send all the troubleshooting questions to you from now on!!

Regards,