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Strange watt meter readings

#1
Recently purchased a $15 watt meter on Amazon that had good reviews.

I used it on my Das Mini Stick scratch build from the plans forum and it was pulling way higher amps than expected.

Motor: QAV2206-1900kv https://hobbyking.com/en_us/qav2206-1900kv-cw.html?___store=en_usbn
Prop: 6045 bull nose
Batt: 3s 1300
Esc: Turnigy Plush 12 amp


Now according to HK this combo should be around 12 amps (from the HK page). I showed 18 +/- amps and 200 +/- watts on the new meter! I have been flying the plane. Quite a few times in fact with no signs of letting the smoke out.

I also tested my FT Mustang w/ NTM 28-30 1200 and 9x4.5 and came out with an as expected 250 watts.

Something doesn't make sense about the Mini Stick test. Is it even possible these numbers are correct? Wouldn't the ESC have burned up in a couple flights with a 50% plus overload? And could the published prop test be so far off? And if the watt meter is junk why do the numbers on the other plane look correct?
 

Snarls

Gravity Tester
#2
Well for one the data on the product page lists an HQ6045 for the test, whereas you're using a 6045 bull nose. So the bull nose could explain a great deal of the increased amp draw. Also motor data should be taken with a grain of salt, especially when directly from the manufacturer and with miniquad motors. I would trust the well reviewed watt meter over one set of thrust tests.

The reason your ESC is no burning up is because your likely not flying at 100% throttle all the time. The rating on the ESC should be the max continuous current it can withstand, but every ESC has a higher burst current that it should be able to handle for limited duration. Also amp draw on the ground in a stationary position will be slightly higher than in the air.
 
#3
Thanks, I started looking at info on the bullnose props. I am new to Electric RC and didn't realize there could be a substantial difference between these types of prop profiles. I had read that Slow Fly props pull more amps, but didn't connect the dots that other prop profiles would make a big difference too.

....and you're correct about reduced throttle. This thing has enough power that full throttle is a little ridiculous and I've only ever used it for a few seconds at a time.

Sounds like it's time to try a different prop. I might order some non-bullnose 6x4's and see if that drops it enough. If not I'll have to drop to 5 inch.
 

rockyboy

Skill Collector
#4
Or you can keep the monster prop on and fly that Das Mini Stik like a spooked cat :p


( I LOVE my Das Mini Stik - but on a mildly aggressive motor/prop as a sport flyer, not a full on racer :) )
 
#5
Switched to a 6040 standard prop and it dropped to 13 amps. Slight overload but I'm willing to push it a little since if this one dies it's no huge loss and this model is a lot of fun going fast :black_eyed: