High voltage and High amperage motors?

Esk8 Dev
#1

First I just want to say if I got any facts wrong please feel free to correct what I said.

So I’ve been meaning to start this for awhile now. With the new Stormcore 100D and Rion Tronic coming out a lot of people are moving to higher voltage. What we are missing is a motor that’s not a crazy low kv (90kv Maytech) but also supports the amperages we want.

So back story on why you might want to run higher voltage on your board.

Summary

The main thing (in my mind) is more speed without a decrease in torque. We all know upping your gearing so you can hit higher speeds makes your torque drop away. Higher voltage solves that by adding speed by putting more volts into the motor making it spin faster at the same gearing.

Another reason to go higher voltage is the torque. 16s 100amps per motor will be more torque then 12s 100 amps per motor. This is a big thing if you live in a hilly area or just love torque and take offs.

Finally, efficiency. The higher the voltage the more range you will get. A 13s4p battery will get more range then a 12s4p battery, if the same cells are used and you were to ride both batteries the exact same. For example (hypothetical so not true but gets the point across) A 13s battery at 60amps will feel the same torque (if geared for the same top speed) as a matching 12s battery with 70amps being used. This means the 13s uses less power to reach the same torque and top speeds as the 12s battery which leads to a better mpg aka wh/mi or wh/km.

Alright, on to the real point

So here’s the real point. We don’t have motors that can do these voltages. Alright yes we have motors built for cars like Nissan Leafs and Tesla’s, but those don’t fit our application.

Really speaking, we can’t get those motors we want without buying in a large quantity.

For example I was all set to do a KDE Motor Groupbuy (suppliers of Hoyt motors) for custom made 63100 25s 250a rated motors. These would’ve been the bees knees, but they cost $386 dollars per motor. Now you might be saying, “Hey that’s pricy but if it lives up to its expectations then why not?” Well I’ll tell you why.

KDE wants $2250 as payment for the custom motor design and tooling etc. This means that if we bought 20 motors (10 sets) it would cost $498.5 per motor excluding shipping. If we sold/bought 24 sets (48 motors) it would cost
~$438 per motor. In my head I knew that personally, I’d sell stuff and I’d buy 2-4 motors at that cost. But I knew that seriously speaking, we wouldn’t make up that other 44-46 motors.

The point of this thread was so that we could help each other and try to find or have made a motor that fits all our high voltage needs.

Big shoutout to @ahrav for proofreading this mess of words

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Ideal motors for 18s config
Spintend 75V/200A Ubox (Based on 75V/300A VESC)and Uni1 Introduction !
#2

@Arzamenable the above talks about those motors I was telling you about.

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#3

I’d also like to know, what is a typical failure mode if using, say a 190Kv 6380, at something like 17S and pushing high power levels. What would be the first signs of failure? If none, then if you kept increasing the voltage and speed, then what would be? I just wonder if it’d be a thermal problem or a mechanical problem like bearing-related or magnets demagnetizing or stator saturating, or what would be the first signs that the voltage is too high?

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#4

One thing I think won’t matter as much (for reasonable voltages) is the winding insulation, as I feel like the biggest stress on it is the temperature.

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#5

without practical proof, the same problems you’d face on our currently used motors would be as present on the bigger ones. More power doesn’t neacesarly mean higher speed, but like most bldc motors, the bearing is the usual point of failure.

Regarding the stator saturation, its more current related than voltage. The current flowing creates the force in the magnetic field not the voltage. Smaller motor(less copper) saturate alot faster, So if you follow what seems to be the topic here of a bigger motor, you’d have to push alot of current before that happen. I’ve only managed to do it once (around 50A) on a smaller SK3 motor

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#6

I totally think the first issue would be overheating.
Heat produced = V^2/R… right?
In the case of higher power, we’d be moving away from 12s systems to upwards of 20s so an increase in voltage therefore more heat produced

I was thinking the only possible solution to handle overheating and more voltage was to have either or a combination of:

  1. Increase windings
  2. Thicker gauge armature wires

Overall fatter motor due to the increase in size of the stator

But I could definitely be wrong

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#7

It will probably start to be a concern post 100V.
Copper losses and skin effect is probably a bigger concern

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#8

A lower Kv motor would have thinner windings (but more turns) than the same motor in a higher Kv, assuming a lot of other details stayed the same

#9

I’m just wondering if my upcoming 16s build on a 4:1 Kaly helical drive and 190kv motors will be fun to ride. I wasn’t aware that Kaly drives can only be used with Kaly Motors smh

Edit: Ernesto told me himself that 16s on 190kv would have more torque than 12s on the same motor. This makes me feel better but I’m not sure.

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#10

We had this discussion before. The conclusion was that there are no real life benefits of HV. It is cool that it’s possible now and all that, but in my opinion it’s not more than a hype. I’m experimenting by myself with HV but so far I can’t see any substantial benefits. You won’t get more torque, range or power with HV. Everything depends on the cell number, maximum amperage, gearing, and motor KV. IMHO there is especially no need for HV motors. Our 63100 Titan motors can take 16S @ >100A. That’s about 6kW. I don’t think that anybody really needs more than 6kW per motor, even if it’s fun to build such things. ATM it would be more interesting for me to see reliable 20S VESCs. That’s more a bottleneck than the motors, if you ask me.

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#11

Motor torque is a function of amps. It does not go up with more voltage.
Wheel torque can be increased with higher voltage, if higher gearing is used.

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#12

So with unchanged gearing, the only difference would be top speed?

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#13

Yep. Will not accelerate any faster or climb hills any better.

A high voltage application that makes sense is going for the highest gear ratio you can and then throwing enough voltage to get the top speed you want.

2WD/12s setups get thermally limited pretty fast if you ride hard/fast. More voltage without changing anything else will not help with that.

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#14

Am I missing something?
Whats wrong with changing the gearing for more torque?

You’d get more torque for the same top speed
And probably can even get more torque AND more top speed

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#15

These would be much more reasonably priced if you aimed for 20s and 100 or 150 amps.
Even that is more than people will likely need.

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#16

Another issue to think of is the mechanical limitations of the outrunner topology. If you increase the voltage without lowering the KV, you’re getting up into some crazy RPM (not to mention ERPM). There are already instances of resonance-related issues with unsupported cans at our current RPM levels, and that’s just gonna get worse.

Plus eventually the centrifugal forces are going to be enough to distort the cans.

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#17

What about a lower KV motor and same gearing? Would that make any difference at all?

#18

Yes. That works very well. Lower KV = more torque, and the higher voltage will offset the lower maximum RPM.

#19

Faster charging on potentially cheaper chargers, assuming same wh battery? Easier to charge high amounts of power?
More low speed motor amps for less battery amps?
Less fried drv chips due to voltage spikes, assuming esc run under limits?

@tipsy amps do drop with higher voltage. Only the battery amps.
10 amps at 100v will send 1000W to the motor.
The motor at low speed will maybe run at 10V@100A. Plenty i’d say, and that can come from ?S1P 50E battery

If i talk bullshit someone correct me

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#20

Yes, but you need a motor with a KV low enough not to grenade from the RPM that 100v will cause.

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