[REC] True 4-5kWcont DD hub @52V for high torque

[john61ct]

Looking for recommendations on motors to investigate. Ideally specific models with reliable supplier links, I am in the US.

You could also just shout out brand / mfg if you don't want to spec a model#.

Will not say price is "no object", but robust build quality is more important.

DD hub motors only please, ideally those suited for either front & rear (possible 2WD rig), but whatevs, **please** avoid the "front dangerous" issues, well aware. Same with advice wrt gearing, mid drive motors etc, please refrain for now, this thread is for **DD hub motor** reco's and related info only, please.

Use case is tandem / cargo, 500lb total, from sea level up into high mountain country, e.g. CO / UT.

26-29"/700 2" minimum, maybe even 3" or fatties, gravel trails, desert BLM and forestry roads.

Edit: obviously as tire gets fatter, reduce rim diameter. Maybe a truly plush bouncy ride would allow to reduce total diameter to get more torque back? Pretty sure no other suspension. . .

So obviously low-end torque is the top priority, will need a robust steel frame, and I'm planning on ultra strong wheels & fork, double torque arms etc to handle the high torque.

Top speed desired is 20mph max, even on the flats, will usually be keeping under 15mph.

Wh/mile range efficiency, optimized for say 12-15mph on smooth flat roads, is **critical** , for desert travel, that and robust build quality, reliability,

I also need lots of range, survival may be at stake

So the motor: looking for 4,000W (minimum) **actual continuous** in cold ambients without breaking a sweat, really 5k would be better.

True this is joyous overkill, even while climbing hills I likely will run under 2500W, 99.9% of the time.

But extra margin is needed for hotter weather / steeper mountain passes / extra human aboard, etc, plus added longevity for usually maintaining a high margin of overhead and lower stress on the motor.

Furthermore, Dogman Dan says maintaining 15-18mph while climbing is important for efficiency & reducing the motor's waste heat. It will take "some time" for me to get fit enough to keep a good cadence at human-power-helping to get up over the big passes.

A Grin CAv3 will de-rate as needed to protect the motor, temp sensing etc.

 

[john61ct]

Rather than low gearing, my idea is to use a very low-voltage / high-current, low-speed / high-torque **winding** for the DD hub motor(s), goal being a very low Kv rating, slow acceleration is just fine.

The pack will be 52-54V, high discharge C-rate cells, thick wiring, well over 40Ah capacity. I'm determined the battery will **not** be the weak link, plus I need that range anyway.

Of course, the ideal would be to focus on great low-end torque at 52V now, and then be able to tweak up to a higher voltage later on to see if I can get a little faster top speed without sacrificing needed torque.

(Does that make sense? Would that require rewinding the motor?)

 

[john61ct]

Example controller:

"Lyen Edition Muscular High Current Controller"

24x IRFB 100V 4110 N-Channel MOSFETs

Just under $400 delivered, including CAv3 connector, regenerative braking disable jumper and programming adapter.

EC-244110-LYEN EDITION
Start immediate controller
Chipset: GPM8F311A
Circuit board version: KH324 series
24 x genuine IRFB 4110 MOSFET N-CH 100V for more information about the FET:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFB4110PBF-ND
100A is the current rate
Low voltage cut-off: User programmable (optional USB-TTL programming
adapter required $15)
Battery and motor phase wires gauge size: 10AWG
Dimension: 8.27" x 4.65" x 2.95" (210mm x 118mm x 75mm) plus mounting extensions
Total weight: 4 lbs 1 oz

EDIT: 24V to 88V nominal (up to 100V fully charged). So using this for 48V input now, then going to 72V is perfectly fine




if approaching 100A, CAv3 + temp probe on the FETs for de-rating protection

______
Of course if there are better production ready controllers out there suited to this use case,

or just as powerful and robust build quality at a lower price,

reco's would be most welcome.

______
Previous thread on voltage issue, for reference, please don't try to make the case for higher voltages here, let's keep it to that thread:
https://endless-sphere.com/forums/viewtopic.php?p=1495908#p1495908

Also, for speed freaks to discuss there, the higher-voltage "twin sister" Lyen Freeway Speed controller

 

[Hillhater]

26-29"/700 2"minimum, maybe even 3" fatties,
Top speed desired is 20mph max, even on the flats, will usually be keeping under 15mph.

Side note: how do I find out my target rpm range, given the data so far?

Sorry john, i am not familiar with DD motors enough to recommend anything, but i can help with your rpm question...
A 29” tire dia at 20 mph, will be running at 232 rpm.
From this.....
20mph/60 = 0.33 miles/min ..or = 1760 feet/min
29” = 7.589 ft roll out per rev
1760/7.589 = 232 rev per min......at 20 mph. ....( this will vary depending on your exact tire rolling dia.)
Obviously 10 mph would be at half that rpm.

PS...what do you have in mind when you say “lots of range” ?
I fear your 54v, 40Ah (2 kWh) pack wont take you much more than 10 miles !
Even averaging 2500W at 15 mph you will be burning near 200Wh per mile....5 -6 miles per kWh .
So even a 15 mile run ( one hour ?) would need 3 kwh batttery pack ( approx 40lbs of weight) !
Just be aware of pack requirements for high power and “lots of range” . :wink:

 

[john61ct]

Found this:
Tire Size, RPM, Speed, and Differential Ratio Calculator http://www.advanced-ev.com/Calculators/TireSize

 

[john61ct]

what do you have in mind when you say “lots of range” ?
I fear your 54v, 40Ah (2 kWh) pack wont take you much more than 10 miles !
Even averaging 2500W at 15 mph you will be burning near 200Wh per mile....5 -6 miles per kWh .
So even a 15 mile run ( one hour ?) would need 3 kwh batttery pack ( approx 40lbs of weight)

Wow.
Well, I just need that high level of power to be available when needed.

Which besides start-from-stop, is on those dreaded hills (eponysterical handle there BTW

I really doubt the **average** power draw will be anywhere near even 1500W?

Plus human power factor, if (as) I get fitter.

But I need to have a look at the Grin modeling tool. . .

 

[Hillhater]

Obviously, your range will depend on many factors, but i was just using the data you indicated ..hills from sea level to high mountain country,..500lbs, dirt roads, fat tires, etc etc.and “survival may be at stake”...+ not wanting the battery to limit you.
Human input can extend range, but realisticly, on a 500lb bike, uphill, ..it wont be a big factor.
So what “range” do you expect you will want ?

 

[john61ct]

More like, how far away from the supplies source will I be able to setup camp?

The really big mountain climbs will only be when actually traveling longer distances, between encampments.

Most trips will be shuttling back and forth for water, food & fuel.

 

[John in CR]

...high-torque **winding** for the DD hub motor(s)...

As explained in the other thread, there is no such thing as a high torque winding. If a motor is wound to be slow, then yes it will have more torque per amp, however, it's current handling will decrease commensurately due to longer thinner copper, so you end up back in exactly the same position.

The motor that would come closest to meeting your needs would be the QS 273x40 spoke motor, but it will fall short on the steep climbs pushing your 400lb load, because you need almost 2kw continuous at under 150rpm. The high cogging torque to overcome and 20kg weight would make it impractical as well as inefficient at low rpm. Their much heavier double wide could probably make the low rpm torque you need continuously, but the fat moto tire required for their build on rim wouldn't work on a bike, and it would be even worse in terms of cogging torque and low rpm efficiency.