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?

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...

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

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

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.

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!

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?

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.

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)...

I would agree.

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

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.

[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.

A continuing challenge for electric motor manufacturers and motor users is delivering more shaft power while using less input power, which simply put means increasing the motor's efficiency. Motor efficiency improvements extend the life of battery-powered products, save on energy costs and reduce the amount of heat that can cause damage and increase in-field service and warranty costs. Higher power efficiency also means lower internal power losses.

1. Copper winding (function of conductivity of copper and the resistance of the stator coils)
2. Coulomb friction (brushes, bearings and shaft seals, etc.)
3. Viscous friction (bearing lubrication, certain materials damping characteristic as a function of speed)
4. Hysteresis (magnetic memory in motor's soft iron members)
5. Eddy currents (primarily soft iron losses caused by material type and thickness of laminations, material induction levels, commutation frequencies. Losses vary as a function of speed squared)
6. Windage (aerodynamic effects due to motor geometry and speed)
7. In most applications, the copper winding losses are the largest contributor to an inefficient motor. These losses are computed by multiplying the input current squared by the winding resistance of the stator. The conductivity and resistance of copper are among the lowest per foot of any current carrying material. Only at higher speeds do eddy current losses become significant.

I think I found my answer. I think.

Sorry for the triple post guys.............

Specs on the NEU 1515 series are as follows:

MODEL RPM/V V Range Max Current Draw
1515/1Y 2200 7-25 100
1515/2.5D 1700 7-40 100
1515/1.5Y 1500 7-35 85
1515/3D 1360 7-45 85
1515/2Y 1100 7-50 75

So a 1515/1Y Has a recommended Voltage range of 7-25V and as expected (in part) the voltage range increases as the # winds increases. (and the current draw falls)

Procharged, yea that's some good info.

My understanding of iron losses is that they increase with the frequency of eddy current generation. Everytime the poles intersect eddy currents are generated. In a higher pole motor the intersections are occuring faster for a given RPM than in a lower pole motor.

Yes, lower Kv generally permits higher voltage which in turn results in lower current.

High current is an enemy of efficiency. Ohms law shows that the voltage drop over a given resistance is lower for less current drawn. ie. if you are pulling alot of current, you are loosing more power to circuit resistance. This is why power distribution is done at high voltage.

If you run a lower kv motor then it is in the effecency range.

Hey guys, R/C equipment aside, I thought we couldn't pass approx. 30 volts due to it's potential to cause some serious damage, even death, if a mishap were to occur. Any other info on that?

I myself never heard of that. I have in the 40s on one truck. The spark is loud on first hook up.

I know in Germany one requires some special permit to work with more than 10S systems...

That's kinda low. If you mean death by electrocution; personally, I don't "feel" anything less than 60-65v, and even then, it's a very faint tingle. It's not voltage that kills you, it's current. And it takes ~15mA to kill someone. And given our bodies are in the 10-15 Mega-ohms of resistance, it would take quite a bit to produce 15mA of flow. There are other factors in this, but I won't continue rambling. :)

Yes we know it's current, a by product of voltage. In the above post Aragon mentioned the 37v threshold, and that is what rings the bell. There has to be a reason for the permitting requirement. You have to remember somebody may have wet hands, or drive through water, or something of the like.

Why would they make an esc for 12s lipo or even 15s lipo?
15s lipo is some powerful voltage. Now that would make a car zing.

To fill demand. Heli and plane guys are running upto 15S these days. High current is a very bad thing in a 3D heli, so HV is a must for high power setups (>2kw).

While there may seem to be many people wanting high-V systems out there, the vast majority of truck/car systems still run relatively low voltage systems. Most of the electric vehicles are still designed to use NiMH cells, so the replacement lipos are still between 2s and 5s. Manufacturers are going to build for the majority, not the minority. Until more electric vehicles start using high voltage the choices for ESCs that can handle that will be a niche market.

True. In fact I've taken 2-3 50,000 volt hits in my life. All from high-performance 1:1 scale ignition systems.

I've also taken several 120v hits hits while rewiring electrical systems in buildings. The 50,000v hits tingle.....they take away feeling for a minute or two whereas the 120v hits (higher current) hurt more and tingle less. .....if that makes sense to you all.............

So yes, it's the current that gets you!

I think the escs will grow to fit the demand. As more electric make the speed
record more will want to be part of that.

Not only for speed freaks, but there is a definite advantage to high voltage over high current and as brushless becomes more mainstream, I think you'll see more HV setups. It's just gotta go from niche to mainstream...

Well, alot of chargers do 12S lipo's now-a-days. 12S Lipo is 44.4V nominal, 50.4 after a charge.

I'm sure there are some motors out there that accept that voltage...

Castle has an ESC that handles 12S too (Pheonix HV line).

I agree. Same as the heli scene. A year ago 15S ESCs were a dream. Now it's a reality with the Power Jazz. A few years ago ESCs couldn't run outrunners. Now it is very much mainstream.

What really needs to happen is car makers need to start putting out 1:8 electrics. So long as custom conversions remain the only route to 1:8 electric it will stay niche for a long time. Same story with the heli scene. A year ago there were very few larger than 30 size electric kits available, yet the conversion scene was very much happening - now there are more than 5 out of the box large electrics that are very affordable.

In a few more years nitro will be a niche market. :D

Hi,

I just discovered this thread. I'm thinking (or on the verge of) going for HV & lower current setup. I live in the tropics & the heat from lower voltage - high current setup really causes havoc (fried 5 esc as proof). I am also also in the same shoes as knotted. I want to try 8S with a 12XL or 1940 10wind on a 1/8 buggy. The esc I'm comtemplating is either a BK3695 or BK36120. However, I'm wary of the 36120 as somehow, it can only do 42000rpm max. (info from Mike's store).

In addition, a Lipo under load is likely to drop some voltage. From my limited expereince looking at my eagletree data logger using some Kokam 20C cells, I see something like 3.2V per cell. If one is to use 8S under load, the total voltage will be approx. 25.6V. Is this logical ?

Personally, I think higher voltage & lower current is the way to go for a more stable system at least in my part of the world. For now, it's still all theory for me. I will try & find out soon enough.

8S 4000mah capacity should be similar to 4S 8000mah with less losses due to heat. that's waht I want to try out next.

Regards,
Joe Ling

The 36120 has survived a 9s run and 26 cells. I hooked 12s up on it and it
destroyed a spur in about a sec with tires off ground. It was a rx problem.

I plan to run 8S too. I hope the cells don't drop to 3.2V/cell. I guess it depends on the cells. I hope to get away with running 8S 2100 mah, but we'll see if that works out...

What do you think of the MGM 16024? You said in another thread that you fried one of them and I was curious if you found them to be problematic...

I ran a MGM 16024. Would not recommend it to anyone. It may be the best controller in the wotld, but I wouldn't know because it's been off at MGM for repairs for four months now. Unfortunately I'm not an isolated case either.

Hi coolahndcountry,

Thanks for the info.

Hi Aragon,

I fried a 16160 (the one with lower voltage rating) while using a 5S. My impression is that the MGM cannot really take much abuse at all. BK took more abuse. There is no customer support to speak of. I emailed MGM direct & after a few correspondence, they just seemed to trail off & I get no response from them. In the end, I sent all the broken esc back to Mike & ask him to help.

So, I'm leaning more towards the BK.

Regards,
Joe Ling

That's a real pity. Apparently the BKs don't do more than 2 poles. Are there any other 8S options that do more than 2 poles? (apart from a Jazz which won't be as smooth)

Why not run CC phoenix HV esc & mechanical brakes?