No, you did it wrong. Also, the method is not "flawed". While starter circuit is engaged you need to check voltage AT the two solenoid posts and compare the two. Not just the drop at the battery. You should do the same with the master solenoid too because you may be dropping there. If you prefer listening to other "experts", then please disregard.
Guys, thanks for sticking around. I was a one man show trying to get these voltages and one arm short of it being easier. This is what I did:
I built 2 x 18 ga. wire, 4 ft each with alligator clips at each end. I disconnected the positive going to the starter at the starter, connected an alligator clip to the positive lead going to the starter and connected the other end to the positive of the light. I connected the negative of the light to the alligator clip of the other wire and connected the other end of that wire's alligator clip to various other grounding points (negative of the starter, engine case ground, firewall ground, negative at a/c battery). The light was next to me on the wing so that I could engage the starter with one hand and take voltages with the other. I also messed up and provided the wrong readings.
Battery Voltage with everything off - 12.2
Battery Voltage with Master on and Dynon D10A and MicroEncoder ON- 11.7
Battery Voltage with Starter engaged- 11.4
Voltage at Upstream side of Master solenoid and Starter solenoid whith starter engaged-11.4
Voltage at Starter with Starter engaged- 11.34
That would mean a 0.06V drop across the starter solenoid right?
My starter solenoid is in a very hard and awkward place to get to and by myself was not able to get a voltage drop across the solenoids while turning the key. I did manage to take a voltage on the upstream post side of the starter solenoid with starter engaged (11.4 V, same as upstream and downstream posts of Master solenoid and same as battery). I was not able to reach the 'out' post of the starter solenoid, but it is connected directly to the starter, so in my mind, in essence, the voltage at the starter (11.34) would be the same...correct?
I suppose I can determine the resistance and amp draw of the light then apply the formulas assuming a 200 to 250 amp draw from from starter to determine what the voltage drop at the starter solenoid would be seeing as that's where the drop seems to be occurring (0.06V) with the lamp hooked up. I think it's a 40W light so as someone said, about 5 amps. Seeing as 5 amps is 40 times less than 200 amps, can I assume that with a 0.06 V drop with 5 amps, the voltage drop would be 2.5V with the 200 amp starter connected. What should the voltage drop be across a good starter solenoid be?
I was drawing down to 6 or so Volts at the battery with the starter connected and engaged but that was after holding the key on for a second and the prop not being able to push through the compression stroke. Skytech says I should have at least 11V at the battery and 10V at the starter.
It is pretty cold here (-10F or so) and my battery checked in at 170 CCA which is what Odessey says it should be but maybe its not enough in my application. Maybe I should preheat the battery a bit in the winter months prior to starting.
I know it sounds logical and cheaper to change the starter solenoid but let me tell you, the builder did not take into account having to do that eventually. Although a wound starter is a more expensive fix, it would be a thousand times easier and from what I have read from others with similar 'bump and start' type symptoms, going to a wound starter made the difference. But others with those same symptoms replaced the solenoid and had success too.
What does connecting a battery booster pack to the battery for start do? The plane starts like a champ with a booster pack. Is it purely adding cranking amps?