Efficiency. Geared vs Direct drive hub motors

I recently purchased two new ebikes. The Radpower Radcity and the Elux Newport. The Radcity is a direct drive 750 watt 48 volt 10 amp bike. The Elux Newport is a geared 750 watt 48 volt 10 amp bike. Both are almost the same weight and both ride great but the Newport (geared) motor ebike gets about a third more range. Direct Drive motors have some drag but I thought the decreased efficiency due to drag might be offset by regen braking. But not. The geared motor ebike (Elux) has much better range. Any thoughts. I like both bikes but I'm really surprised by the range difference.
https://www.eluxbikes.com/newport
https://www.radpowerbikes.com/products/radcity-electric-commuter-bike?variant=27902381057

The geared motor must be better matched to the load versus speed of the bike it's installed on. I'm guessing the no-load speed of your direct drive bike is way too high for its available power to get the bike up into the efficiency sweet spot of 75-80% of no-load speed. The geared hub probably comes a lot closer to doing this.

Yep, other than differences in height (wind drag) and rolling resistance (tires), the only reason for that much shorter range with a DD hub is riding it out of its efficient speed zone. I can see another possible reason: both batteries may not have the same capacity, despite what is spec.

Repeat the test faster. Have another rider to accompany using the other bike. If you do both rides yourself, time the course.

Yes, no two batteries are the same.
Measure the wh used on each bike, and the drain on the pack will also depend on the topography of the test route.
A hilly route will favour the gear motor more than the DD.

Yes, do a discharge test on the batteries.
If the controllers are truely the same, the only way for that great a variance in range is one battery is delivering more capacity than the other.

Yep, measure the watthours with some kind of wattmeter. Did you pedal? DD is very unefficient at low speeds and starts if you don"t pedal at all. Expecially lot of stand still starts and hills are no good for a DD without pedaling. DD works well if you stay above 10mph all the time and pedal hard on hills and starts. Stay above 10mph on hills.
Nice looking bike that Radcity. I am considering myself to build another rear wheel with geared hub, just to test it and compare.

Let me guess, the motors operate at different speeds? I'm guessing your DD is going at least a few miles per hour faster.

I am a huge geared motor fan but in a competition between a DD vs a geared at exactly the same speed with no pedaling will always have the DD winning unless the DD is a real piece of crap, like a conhis motor or a magic pie.

The most efficient geared motor on the market achieves around 83-85% peak efficiency ( MAC with new 0.27mm lams ). The best DD on the market will return up to 91% efficiency and then also have regen.

Go on the ebikes.ca simulator and you can see what i am saying in action, and yes.. the simulator is pretty true to real life.
http://www.ebikes.ca/tools/simulator.html

The one thing geared motors always do is have more power per pound of weight. But only an extremely expensive and exotic geared hub motor could ever hope to achieve the efficiency that a direct drive motor could.

neptronix said:

I am a huge geared motor fan but in a competition between a DD vs a geared at exactly the same speed with no pedaling will always have the DD winning unless the DD is a real piece of crap, like a conhis motor or a magic pie.

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Why is the conhis and magic pie motors pieces of crap?

Conhis sells a little 250-350W DD hub that doesn't even hit 80% efficiency and is generally the worst DD hub you can buy.
The magic pie has a severe amount of end turn losses and i don't believe they have upgraded the motor to have 0.35mm laminations yet and are still using 0.5mm. The efficiency is lower than oldschool thick lamination 9C motors.

When there are better designs on the market... with better power density and efficiency at a fractional additional cost.. it's not worth playing with these older motors at all because what you save on motor ( $20? ), you spend on additional battery so that you can get the same distance.

Like, if a conhis mini DD uses 10% more energy, i gotta buy a 10% bigger battery to go the same distance and i don't end up saving any money that way.

This just means the seller of the DD bike chose the wrong wind for the controller. Because of the gears, (higher motor rpm)a geared motor is less sensitive to the winding. The underpowered DD get to lug.

It may also be a lot to do with how you ride. If you ride rolling hills, the geared will coast better down the hills, and it will definitely outshine most DD motors in any kind of city riding, with lots of starts and stops. This could be 20% difference, even with the exact same top speeds.

My opinion, shared by very few, is that in a big wheel, a dd motor performs better on hills and stop and go, if the wind is slower. This Does NOT apply, if you power up the dd with more than 1000w.

Anyway,, test your efficiency on a long uninterrupted ride. Bet at the same speed, they are nearly the same efficiency then. Definitely, if you ride city, you want the geared, unless you are overloading one.

Lot of ifs and buts in that reply. But this is what I do,, steer a 300 pound guy to a slow wind dd, and everybody else to the geared. E bike kit can't make money if the fat guy buys the geared motor and fries it. But everybody else, will love the geared motor better. Faster take offs, longer range in city riding, and a lighter wheel.

I'm the ultimate contrarian. I have a very fast wound DD that does 40mph on 12S Lipo, i feed it a ton of amps, and it's the most efficient motor i've ever owned. And i'm pretty sure i've ran 10 motors of various types and windings by now. As far as i know, it is the most efficient direct drive hub on the market, hitting 91% efficiency at peak on the 4T super fast winding!

I really all depends on the motor. A dyno sheet, a turnigy watt meter or CA, and/or the ebikes.ca sim will tell you a lot about a motor, pre purchase and post purchase. One thing i've learned is that generalities about motors are out the window - their designs vary a lot and their RPM/load sweet spots are all over the map.

So if you want a high efficient setup, start looking at the ebikes.ca simulator and dyno sheets. Correlate the peak efficiency on the dyno sheet or ebikes.ca sim with the speed you're going to travel at the most. ebikes.ca sim will help you translate RPMs into wheel speeds too. It's an amazing tool that is underused these days!!

neptronix - Well thats good to know. I bought a dd kit from Conhismotor that states 1500W and I pull 2200W at most with its paired 45A sinew cont. but on average I pull 1200W-1500W with its KT display temps normal.

If I am not mistaken neptronix, your dd motor is the Leaf 1500W?

I will end up selling this conhismotor kit and going to either the Leaf 1500W or the new MXUS 5000W, depending on a few things. I'd love to get a Kelly sw cont.

In the meantime I've ridden about 150km on it.

Edit - +1 on using ebikes.ca motor simulator, another good tool is the trip sim beta because it using Google Maps you can trace your route and view all the data as well.

The path was the Norwottuck rail trail from Northampton Mass to Amherst Mass round trip about 18 miles. No significant elevation till Amherst. I rode at almost the same speed with plenty of PAS (peddling) especially on the DD bike (Radcity) because I was worried of depleting the battery before I returned. The Radcity rides well but I'm disappointed by the poor range. The Radcity is equipped with a 48V 11.6Ah Li-ion with 30 Amp Continuous BMS Panasonic 2900 mAh Cells. The Elux (geared motor) bike has 10 amp 480 wh Lithium Manganese Oxide battery.
Both bikes ride well but the Radcity's range disappoints.
http://www.mass.gov/eea/agencies/dcr/massparks/region-west/norwottuck-rail-trail.html

To do a range comparison, you'd have to do it with zero pedalling.

If you pedal, the variation in human input is great enough to cause a difference in range.


You'd also need to do the test several times with each bike to verify wind/etc are not causing any difference. Over a longer trip even a little breeze could cause enough drag (or push/boost) to cause a great deal of range difference.



Note that the battery specs you give are incomplete, and different specs portions are given for each battery. You'd need to get the complete specs from each vendor, or perform tests on each one to get the same specs from eacn one, to compare them.


Otherwise the range test of motor vs motor could only be done fairly by using the same battery on both bikes, because you don't know that the battery itself isn't the cause of the difference in range.

So,,, what you found out is one battery is better than the other? You did not compare efficiency, unless both used the same battery, or,, you have real wh/mi numbers from a watt meter.

Experiments with two variables are junk science.

Efficiency is all about power in/power out.

At 0 RPM (or poles shifts/second) no matter how much power you put in, efficiency = 0%. Geared or Direct Drive (DD).

There is generally a non-linear curve to peak efficiency speed with any given motor beginning at zero. Once you reach that peak efficiency speed it typically doesn't drop much above that for a ways out.

While many equal power rated DD motors tend to have more poles and copper than an equivalent power rated geared motor, they still tend to be disadvantaged on efficiency below the peak level. For example if a DD motor has 64 poles and a 5:1 Geared motor has 32, the DD has to reach 2.5 * the RPM as the Geared motor to reach that pole shifts/second speed of the Geared motor. Granted there are many other variables that come into play, but those are the key ones in efficiency.

Now if you're riding a steady speed all the time and that steady speed is close to the peak efficiency its going to be efficient. Obviously there is a little loss, maybe 1-3% on a Geared hub.

But in the real world we start, stop, cruising at different speeds. The Geared motor will be in an efficient zone more of the time than the DD will. Its just that simple.

And yes, on an equal vehicle the same route, same speed profile, same controller & battery, I found the Geared motor to use about 65% of the power the DD did. Both were windings of "equal speed" ratings. What really suprised me was testing a BBS02 under the same conditions; used less than half the power of the DD. These tests were run over a period of many months, very repetitively. FWIW, the BBS02 was faster in both acceleration and top speed as well.

Thanks for all the advice. Both bikes are great, both have different qualities that meet my needs. I use the Radcity for around town and the Elux for longer bike rides.

Yer on your way to the 12 step program. Many of us here on ES have 6 or more bikes, each one tailored to a specific type of riding conditions.

After the fire, I'm down to just 3, one a street cargo bike, the other two dirt. One dirt bike is for pedaling with good assist on single track, the other is more like just hang on and grin as you blast down a dirt road.

I wouldn't say one is more efficient than the other, just that riding one way takes a tiny bit of power, and the other sucks a battery dry in no time. I keep both in the high efficiency rpm, but the fast bike loses its power to the wind.

dogman dan said:

After the fire,.

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After the fire???

https://endless-sphere.com/forums/search.php?keywords=fire&terms=all&author=dogman+dan&sc=1&sf=all&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

How does one ride in the most efficient zone?

I am playing around with the motor simulator and it seems at any throttle level is fine, but to get a lasting wh/km the slower you go is better.

markz said:

How does one ride in the most efficient zone?

I am playing around with the motor simulator and it seems at any throttle level is fine, but to get a lasting wh/km the slower you go is better.

Click to expand...

The simulator isn't exactly perfect. For example look at the default when you open it, then set the throttle to 10% and Simulate. In the Green cell "Efficiency" you'll get 44.8% Efficiency @ 2.9 KPH. Then try 50% Throttle, for 72.5% E, and 21.5 KPH.

Then try the same throttle settings at 5% grade.

The range factors in rolling & aero drag. Rolling drag increases at a constant rate with speed. Aero drag increases at a rate of a square of the speed.

Generally up to about 10 MPH rolling drag is greater than , and above 10 MPH aero drag is greater than rolling drag. From 10 to 15 MPH, aero drag increases by 225%.

Therefore the Power out required increases which cuts the overall range down. So unless you're needing to go faster than say 20 MPH, you'll always go farther with a geared hub over a DD, except maybe on a long downhill.

I play with that sim a lot!
To me it seems the slope has a lot to do with efficiency.
Today the wind was strong and I got 1/3 less range then usual.

markz said:

How does one ride in the most efficient zone?

I am playing around with the motor simulator and it seems at any throttle level is fine, but to get a lasting wh/km the slower you go is better.

Click to expand...

Well there are two parts to the "efficiency"....

A. The motor efficiency and well does it convert the energy from your battery to power at the wheel.

B. Drag...and there are several components to the drag equation one of which is pushing air out of the way...and the slower you go the less "air" drag you have. Just FYI, air drag increase at a rate equal to the velocity squared so the drag at 10 mph almost doubles when you go to 14 mph.

Want max efficiency, get a geared hub motor like a 12T MAC so the motor spins really fast and then ride really slow. Only problem is efficiency and fun are inversely proportional :lol: .