[ULTIMATE1]

E-Flite Power 110/CC Phoenix HV-85

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Can I run this on a 10 cell Li-po Instructions say 8-S to 9-S will a 10-S Kill the motor?

[Mike Anderson]

Originally Posted by ULTIMATE1

E-Flite Power 110/CC Phoenix HV-85

Can I run this on a 10 cell Li-po Instructions say 8-S to 9-S will a 10-S Kill the motor?

It's not the motor that's affected it's your battery. The max cell count is related to the low voltage cutoff limits for the ESC's. For the Phoenix, for example the highest LVC you can program in is 36 volts. That's based on a per-cell LVC of 3 volts, which is what manufacturers recommend. So 12 cells at 3 volts min is 36 volts, hence the 12 S max allowable cell count.

If you used 14s the 36V LVC would bring cells down to 2.6v/cell, which would shorten their life considerably.

BTW all Phoenix HV's have a 12 cell max cell count.

[rcpilot]

I beleive he is asking if he can run the motor on 10S instead of 8-9. If so, the answer is yes, AS Long as you select a prop that does not draw more amps than the motor is rated for. If you add more cells, you need to go down in size for prop to maintain the same amp draw, if you go lower on cells, you need to go up in size on the prop to get same power.
More cells and less amp draw to get same power is most of the times better than using less cells and higher AMP draw.

[tech1]

Ultimate1,

Same as the other 2 posts, 10S will not be a problem.

Mike,
The motor will have a maximum operating voltage based on its design. If you look at the effeciency curves from the manufacturers the effeciency of a motor will decrease when the voltage is above or below certain levels. Each motor has a sweet spot, in this case 8S to 9S.

RCpilot is correct. Adjust your prop so at 10S the overall power (watts) does not exceed the rating for the motor.
Example with easy math, if your motor was rated for 360watts.
That could be 8s (30Volts) at a 12 amp draw
Or 10S (36volts) at a 10 amp draw

At the same power level, (360watts) the 10S setup would run cooler. The risk comes if you start trying to pull 400 or 500 watts from the motor simply because the battery can now deliver more. This would be equal to leaning out your nitro motor. You can get more power, but in the end it may come at a cost.

[Mike Anderson]

Originally Posted by tech1

Mike, The motor will have a maximum operating voltage based on its design. . . .

When I replied I made a mental assumption the motor would not be the limiting factor, since the question seemed to centred around what the ESC was capable of. I should have stated my assumption up front.

Umm I don't want to start a fight, but the maximum allowable rpm of a motor - it's mechanical limits - dictate it's maximum allowable voltage. Is that what you meant by " . . based on it's design . . ?"

[tech1]

Maximum allowable RPM is only a part of the whole story. (I am not saying you are wrong) The motors RPM is affected from both input and output. Both the battery voltage as well as the load will affect the RPM's. The problem is I could blow a motor mechanically at high RPM's due to stress which I assume is your point. I could also blow it at lower RPM's by overloading it and drawing too much power with a huge prop. I think we in the hobby blow more motors due to the latter reason. Similar to leaning out your nitro engine, there is always the temptation to go faster and develop more power without icreasing the power plant itself.

While it takes a little education, we should be looking at a power system (motors, battery, ESC) in terms of the power rating. (watts) It becomes much easier to see how a perticular system will fit into an application. (either plane or heli)
With Vulcan1, the concern is that a bigger battery can deliver more power into the system. going up 1s is not really a big concern unless the motor was already grossly under rated for the plane it is going in.

[Michael in Toronto]

After some consideration, I will also be using 10S with my E-Flite 110 and CC85amp ESC.

http://www.rcgroups.com/forums/showthread.php?t=944901

I used to use a 17/10 prop on 9 cells, rarely exceeded 1/2 throttle in an 11 pound Spitfire, and everything stayed cool.

I purchased a 17/8 prop for testing.