How high can you go on voltage?

Was thinking of going crazy and running on 8s lipo. A 10 or 11 XL sounds wild on 8s. Can a Neu, Lehner or Feigao handle almost 30 volts? What is the highest voltage that a BL motor can take?

[Dafni]

The motor will never be the limitation when it comes to voltage!
Basically you can put anything on a motor you want, just choose a matching low KV.
KV times Voltage equals rpm, and this should not exceed 40K rpm (as a rule of thumb)

Now the ESC, well, this is a completly different story...

[sleebus.jones]

a 10XL on 8S would be almost at 50,000 rpm....past the "sweet spot" of 35,000 rpm. I think you'd have some pretty serious heating issues. With that voltage a 14XL or 15XL might make more sense.

Sleebus

[Dafni]

If you can find a ESC that can handle 8S, and can afford it, you should try a 1950/12.

[Procharged5.0]

Sounds like an MGM's in your future knotted!

Procharged5.0, your probably right! Along with a Lehner motor, it sounds good. Hopefully, everything will be back in stock soon. Isn't it funny how you can never be satisfied in this hobby? Always need bigger and badder.

[Procharged5.0]

Originally Posted by knotted

Procharged5.0, your probably right! Along with a Lehner motor, it sounds good. Hopefully, everything will be back in stock soon. Isn't it funny how you can never be satisfied in this hobby? Always need bigger and badder.

This hobby is just as bad financially (by scale anyway! LOL!) as my full size car hobby, only it take up less space!

:005:

I don't have my Supermaxx done and yet I'm planning my next project!

[BrianG]

ESC aside, there must be a limit on the voltage. I know the motor kv should be matched so it doesn't exceed the recommended max rpm value, but there must be limits on the dialectric strength of the winding insulators? I have never seen a motor that has a hipot test result, so what is the limit? 80v? 100v?

[Procharged5.0]

NEU lists a max voltage on their spec sheet. Not sure that it's the "MAX" voltage but probably more of a recommended "pracitcal max" voltage for reliable regular usage.

I looked at it last night....it might have been 27v if memory serves correct.

For the 1515/1Y that would be a "loaded" rpm of 59,400. Kind of makes sense.

[BrianG]

It sounds like that "max" voltage is related to the max voltage to achieve an rpm no higher than the max recommended rpm. If so, then all the different winds should have a max voltage rating that is different.

Take for instance a 34 turn feigao with a kv of 490. Does this mean it can take the 71v needed to achieve 35,000 rpm?

Usually, the limiting factor for voltage on any device is the dialelectric strength of the insulator - just like the limiting factor for current is conductor size and/or how much power it can dissipate (but power is more of a voltage and current factor)...

[Procharged5.0]

Originally Posted by BrianG

Usually, the limiting factor for voltage on any device is the dialelectric strength of the insulator - just like the limiting factor for current is conductor size and/or how much power it can dissipate (but power is more of a voltage and current factor)...

I would agree.

Finding the "Max" voltage value is like trying to find the current draw spec on a servo...............:019:

[coolhandcountry]

I think the esc is the big problem. 12s on a motor seemed to be ok. If the spur
would survive would be better. 12xl wanderer on 8s would put you aroudn the 37000 rpm.

There is more than one limiting factor. The ones I know of lie in the ESC, motor, and gearing.

From the ESC's perspective, they're all rated to a max RPM which is a limit imposed by the processing speed of the ESC. Most are rated to 150 000 RPM for a two pole motor, but some can go up to 180 000 or 200 000, and some can't even go over 50 000 RPM. If you run a motor of more than 2 poles the max ESC RPM goes down. 4 pole would be 75 000 RPM, 8 pole about 30 000 RPM, etc. if it is rated to 150 000 for 2 poles.

From the motor's perspective, if it's a 2 poler your first worry becomes bearings. A high quality 2 pole motor should spin over 100k RPM before iron losses become a problem, but I don't think any motors are supplied with ceramic bearings capable of sustaining those speeds. I know of atleast one person that has run a Hacker C40-12T to over 90k RPM with ceramic bearings installed. Unfortunately the motor shaft eventually failed though.

If the motor is a 4 poler, iron losses become a problem at about 60 000 RPM. For an 8 poler, 30 000 RPM, etc.

And the problem that I'll be contending with when I try to run 8S - gearing. If you can't gear down far enough for the speeds you want to achieve, your system is going to run inefficiently which can cause overheating. From my investigating so far, 30 000 - 35 000 RPM seems to be a sweet spot for car conversions given gearing options that are (easily) attainable.

Oh, and of course the ESC will itself also be rated to a max voltage.

[Procharged5.0]

[QUOTE=Aragon]

If the motor is a 4 poler, iron losses become a problem at about 60 000 RPM. For an 8 poler, 30 000 RPM, etc.

QUOTE]

Please explain why the "Iron Losses" occur at a lower rpm with 4 & 8 pole vs 2 pole. I'm not understanding that part.............:032:

Perhaps you could provide a more detailed explanation of what Iron Losses are as well.

Thanks!

Pro.