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Old 05-30-2016, 03:45 AM   #1
npomeroy
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Default 12S vs 10S vs 8S w.r.t. power % and heating

In moderate forward flight my 600 scale AS350 :

With 12S voltage at rpm governed to 1370 rpm, it draws 15A. The CC Edge 60 ESC is giving 70% power and heats up faster than I would like, and the Align MX750 (450 kv) motor gets warm.

I was tempted to re-power with an Xnova 300 kv motor to push the ESC output nearer to 90%. But for half that price I could change to 10S or 8S lipos. By my calculations 10S puts the power up to 85% and 18A, and 8S would put power to 100% and 22A (for the same head speed - I wouldn't mind reducing the HS anyway).

The ESC should stay cooler with power output above 80%, but is there likely to be a significant downside to the higher currents?
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Old 05-30-2016, 05:29 PM   #2
Xrayted
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Quote:
Originally Posted by npomeroy View Post
In moderate forward flight my 600 scale AS350 :

With 12S voltage at rpm governed to 1370 rpm, it draws 15A. The CC Edge 60 ESC is giving 70% power and heats up faster than I would like, and the Align MX750 (450 kv) motor gets warm.

I was tempted to re-power with an Xnova 300 kv motor to push the ESC output nearer to 90%. But for half that price I could change to 10S or 8S lipos. By my calculations 10S puts the power up to 85% and 18A, and 8S would put power to 100% and 22A (for the same head speed - I wouldn't mind reducing the HS anyway).

The ESC should stay cooler with power output above 80%, but is there likely to be a significant downside to the higher currents?
First you have to determine if what you think is hot is really hot at all.

Those current values you quote are very low which typically isnt a problem at all even with lower ESC output values. Its when you are pushing the ESC to its rated current limit at low power out values that serious issues can occur.

Castle ESCs are good up to 212F/100C before going into thermal shutdown, so what temp do the Castle logs show for your flights is the first place I would start.

The same applies to our motors, and many think that because they get uncomfortable to touch for more than a couple seconds something is wrong because they are hot, when the temps are actually normal for an electric motor. They will also heat soak a bit after landing because cooling air is no longer being pulled through them like when they are running.

Most of us won't be able to comfortably touch a motor for more than a second or so at 140F/60C, but that is perfectly normal and cool running heli motor. I would suggest you verify the actual temp with a IR temp tool first before making any changes that aren't really necessary.
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Old 05-30-2016, 06:21 PM   #3
npomeroy
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OK fair points Xrated. I've attached the latest log data. The motor "felt hot" but I could keep my finger on it. The ESC was certainly warming up and may well have stayed safe. Partly why I'd like to get into a higher ESC %output is that the power output is fluctuating a lot, even in fairly smooth flight. In earlier sessions with higher rpm the ESC temperature barely rose, and the % power output was much flatter. Also, I'm working at the upper end of my preferred head speed and I'd IDEALLY like around 1250 rpm and >90% ESC output.

Part of me likes to keep tinkering (maybe I'm procrastinating over the maiden flight with full graphics etc. (I have flown it with the unfinished fuselage shell)) ! And I guess I'm old-school that is suspicious of electronics that "get hot".

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Old 05-30-2016, 08:48 PM   #4
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Yeah, that's not hot at all. Your averaging only 30-40C on the ESC, and the motor is really cool if you can keep your fingers on it for several seconds, especially if enclosed in a scale fuselage!

You are correct that it may be even cooler if you change to a more efficient setup for your desired head speed, but there certainly isn't any urgency to do so due to any heat stress being caused the way it is now based on that data.

If you're like me, you may just want to adjust things for the sake of it being the best it can be and that's ok too!
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