A note on hub motors for hill climbing

[Smaug]

I see in many posts folks recommend mid drive for climbing, since that design uses the chain & sprocket gearing and is in effect more torquey than hub drive motors.

I would like to point out that it really depends on the hub drive arrangement. There is not only the power rating of the motor, how taxed the motor is in that arrangement but the power the controller can pump out and the power the battery pack(s) can pump out. Any of those things can be the limiting factor for hill climbing.

Not only that, but let's not forget that most hub motors are geared, so they can make sufficient torque. (there are some huge direct-drive ones, but even those are more for high speed than high torque and more typical bicycling speeds) One last factor with regards to that is that a hub motor geared for max 20 mph will make more torque than the same motor geared for 25, 28 or 35 mph.

One comparative example from my fleet:

Bike 1: Lectric XP Lite
Battery is 48 V x 7 Ah = 336 Wh. It's a pretty modest battery.
Motor is 350 W sustained, but has a much higher peak power output of 720 W. This means the motor is not very taxed in normal use.
This bike is also limited to 20 mph; no way to unlock it further. Therefore, Lectric chose a motor that was geared down. It provides better torque than one would think and actually does quite well climbing hills. (it has to, because it's a single speed and is geared way too high for the rider to help much with hill-climbing)
Tires are 20", which effectively gears it down, compared to a similar bike with bigger wheel diameter.

Bike 2: Aventon Level.2
Battery is 48 V x 14 Ah = 672 Wh. Twice as powerful as Bike 1.
Motor is 500 W, 750 W peak. About the same peak power as the little motor in the XP Lite! Lectric allows more headroom in their spec. Lectric is not playing The Ratings Game quite as hard....
The bike is assisted up to 28 mph when unlocked from Class 2 to Class 3, so it can't be geared as low, either. Tires are 27.5" diameter, which hurts gearing a bit too.

I don't know about the controller current spec for either bike, but Lectric's display shows instantaneous current, if desired. It seems to be limited to 10 A. I bet the Level.2's controller is not limited so low.

The result is that the XP Lite climbs on motor power just as well or maybe a little better than the more powerful (battery AND motor) Level.2.

Just something to consider before making blanket recommendations for mid drive bikes costing $2700 and up.

 

[HumanPerson]

I just put a 1800w hub motor and a 45amp sabvaton controller on the aventon aventure and everything seems to run cooler with alot more
power delivery in a much smoother way.

I like hub drives.
Also, I believe that each bike/build should have its own purpose.
For instance, my 1500w hub drive with a 52v 35ah battery does 47mph and gets me places alot quicker than a car LOL

Now that the Aventon Aventure has an 1800w hub motor combined with that pure sine wave controller the throttle and EVERYTHING seems much better and more realistic in terms of range and throttle response as well as hill climbing power.


That age old addage certainly comes to mind when i am looking for kits and controllers nowdays compared to
2 years ago...we get what we pay for...
That being said....Research Research Research...there is so much to learn about these ebikes we buy and or Build.

Stay Safe

HP

 

[ETrike]

Thanks for the write up.
There seems to be at least some disparaging of hub motors in general that I've experienced as well.
It is pretty hard to intelligently trash a hub motor application or design when one has yet to witness one in action.
I am also a little tired of hearing how all front hub motors spin out when traction is needed..regardless of the amount of downward force being applied and given that all riders/seating positions are the same.

 

[Ancientcoin]

And quality craftsmanship.
Before I bought my first ebike I watched a video of a supposed (mass produced) "monster" bike. 4x26 tires, big motor, "100 mile range", etc.
It was supposed to be a mountain or trail ready type thing.
On the guys first ride the mid drive motor pulled the chain hard enough to break the (I don't know what it's called) connection between the freewheel and the wheel.
The chain and gears would spin but the wheel wouldn't spin with them.
That had to be a long walk home.

 

[ETrike]

I haven't price-shopped a drive motor between the two designs but my yet-to-be-delivered Bafang 750 Watt is $400 from the manufacturer (which can likely be had for much less) which is likely nowhere near the price of a mid-drive motor from any decent manufacturer.
it could be that my Bafang is junk as well; who knows from day to day. I'll beat the crap out of it and find out for <$400 if the price ever holds in this crazy world that we live in now or certainly in the near future.

 

["A"]

I've been converting regular bicycles into ebikes with hub & mid motor since 2013,
ridden & owned many different bikes with different types of motors.

IME, hub-drive can be well-capable to climb hills for majority of riders, less expensive and less maintenance.

The folks looking for high performing eMTB on black diamond type trails, maybe a mid-drive can save some weight, allow wider gear ratio, but at significant cost and maintenance regiment.

Video narrative is not technical, but does present some valid info:

 

[JerryB]

I am far from a motor expert......never rode a mid drive. I can tell you that I ride my Lectric XP 2.0 nightly.....I ride lots of hills in our area....never have had an issue getting up the hills.....I ride PA 1 on flat roads.....PA 2 or PA3 on hills.........I am a big guy......6'4".....230lbs.......my hub motor does the job.

 

[m@Robertson]

Can a hub motor ebike be made to make do? Yes. To a point. Give the bike 20" wheels. Give it a hi output controller. Make it sturdy internally so it can take being bogged down for a significant chunk of its life. You can get the bike to soldier on. But in steep hills it will never be as capable as a comparable mid drive motor. Will it be as cheap as a hub motor'd bike? Probably not, but neither a BBS02 or TSDZ2 are what you would consider to be particularly expensive. If you are limited to buying a bike off the shelf... yeah sure its going to cost more. Maybe quite a bit more. But buying the bike you can afford is not the same thing as buying the right tool for the job. You can make do. You can settle - and there's nothing wrong with that. But you can't settle for less and make the case that you have not accepted a less-capable solution as a result.

There's a lot more to the why's and wherefores of this, but I'm trying not to repeat myself from earlier exchanges on the same subject.

If anyone wants a challenge: If you are in the Monterey Bay Area, Lets load our bikes up and don't pedal. Lets pick a hill. One would be Prescott Avenue, which is the widely-feared one. See which bike gets up the hill (remember, no pedaling. Only the bike is being tested). Preferably this is also a cargo bike challenge so we can both load up an equivalent amount of cargo... and see who either a) makes it up the hill and perhaps b) which bike survives the event without tearing out its nylon teeth inside the motor (both the BBSHD and Bafang hubs use equivalent gear material). I'll shut off my front hub motor so I don't have an unfair advantage. Or maybe I use a cargo bike that only has one motor to begin with.

But tests shouldn't be necessary as this is really a simple exercise in mechanics. A hub motor is single speed and it is out of its element on a hill - just like a poor human would be trying to ride a fixie on the same steep hill.

Everything has its place. Hub motors are great in many places. Make it a geared hub and that range becomes wider. But that range does not include 'everywhere'.

 

[Smaug]

[...]

If anyone wants a challenge: If you are in the Monterey Bay Area, Lets load our bikes up and don't pedal. Lets pick a hill. One would be Prescott Avenue, which is the widely-feared one. See which bike gets up the hill (remember, no pedaling. Only the bike is being tested). Preferably this is also a cargo bike challenge so we can both load up an equivalent amount of cargo... and see who either a) makes it up the hill and perhaps b) which bike survives the event without tearing out its nylon teeth inside the motor (both the BBSHD and Bafang hubs use equivalent gear material). I'll shut off my front hub motor so I don't have an unfair advantage. Or maybe I use a cargo bike that only has one motor to begin with.

[...]

If we don't pedal, the hub motored bike definitely wins, as the mid drive won't move if not pedaled, right?
I thought all mid drive bikes were Class 1 or Class 3 (but w/o throttle). No?

 

[m@Robertson]

If we don't pedal, the hub motored bike definitely wins, as the mid drive won't move if not pedaled, right?
I thought all mid drive bikes were Class 1 or Class 3 (but w/o throttle). No?

No not at all. Both hubs and mids can have throttles. Certainly all of mine do. This is common for hub motor kits, and uncommon for the pricey factory-manufactured bikes because they are made to conform to EU standards (which is a much bigger market to sell into), which is pedelec-only.

Strictly speaking no class 3 has a throttle. Its pedelec only. Some manufacturers fudge this by putting in a throttle but having it shut off at 20 mph. Which is not conforming to the Class 3 spec but there is enough fudge in legal interpretation in the USA that ... nobody cares and you see them sold all the time.

No pedaling would not be a realistic test of riding, but it would limit the power input purely to the motor, which tests the contention here, that a hub is a functional alternative to a mid drive, which I say it is not in hills (unless lets say you go nuts and do like a 3-5kw QS 203 v3 and put 72v+ behind it).

 

[m@Robertson]

If we don't pedal, the hub motored bike definitely wins, as the mid drive won't move if not pedaled, right?
I thought all mid drive bikes were Class 1 or Class 3 (but w/o throttle). No?

Here is a 750w BBS02 kit. VERY common use and it has a throttle on it.

Bafang BBS02 Mid Drive eBike KIT

Get the Bafang BBS02 for only $525 and transform any bicycle into an electric beast. Do up to 30mph and use the gears of your bike to shift into low and climb big hills.

lunacycle.com

and another:

Bafang BBS02 Custom Build Kit

This Bafang kit contains all the hardware for mounting plus the main electrical cable and the speed sensor kit. All other items can be selected below to build the exact kit you require including throttle, Ebrakes, chainring, display, and optional items. We offer the BBS02 in 3 configurations...

california-ebike.com

one more:

Complete mid drive e-bike kit 48 volt 750 watt Bafang

Everything you need to convert your bike to electric, easy to install, no soldering or electronics knowledge required.

www.empoweredcycles.com

 

[m@Robertson]

And so you know I am not prejudiced against hubs when they are in a place where they shine: I have about 6600 miles on this commuter / pre-cargo-era bike of mine.
Twin 80 Nm motors each with a 35a controller. Battery is 30ah and has a 90a continuous BMS. Look at the gears on this bike. Great big chainring up front. Little cluster in back (doesn't even cover the motor), short cage derailleur even! This bike is meant to be pedaled hard and it is an animal. But it failed in the hills... it could get up them but the groaning and lugging on its way up made it obvious that a bike that would live forever in flat Central CA would not last in steep coastal hills (that is a VERY short version of the story).

Its predecessor. Also a 2x 80 Nm geared hub but without the unified single battery. Note the 60T front chainring.

My original 2wd. I cracked this frame thanks to some ill-advised rack mounting.

My first build. Made almost entirely of spare parts from bikes I upgraded. The yellow is the identical color as the Interceptor in the original Mad Max. Bafang 80 Nm motor again but 48v and 25a this time. Gave it to a friend and it is still her commuter bike across dirt roads in rural Arizona.

There's more, but you get the idea. I'm not a hub hater.

 

[JerryB]

I understand what you guys are sayin....but.....some of us never use throttle only.....I pedal all the time.......if I wanted to not pedal....I would hop on my Artic Cat 400 ATV and go for a nice ride up on the logging roads.

 

[m@Robertson]

I understand what you guys are sayin....but.....some of us never use throttle only.....I pedal all the time.......if I wanted to not pedal....I would hop on my Artic Cat 400 ATV and go for a nice ride up on the logging roads.

Thats not what this is about. The purpose of using a throttle in the test is to test the bike. We care whether the motor can do the job. Not whether the rider can muscle their way up the hill with the assistance of the motor. The use of all-throttle is purely for test purposes. The subject of the thread is about the two types of motors' relative capability.

I generally don't use throttle either, for what its worth. But my use of it is common to what most cargo bikers report they use it for: A blip off the line to get the bike rolling and balanced. Then pedal assist from there. Balance off the line is a big deal with a cargo bike that is loaded with maybe a couple of kids or a grocery cart's worth of supplies.

 

[Hoggdoc]

Can a hub motor ebike be made to make do? Yes. To a point. Give the bike 20" wheels. Give it a hi output controller. Make it sturdy internally so it can take being bogged down for a significant chunk of its life. You can get the bike to soldier on. But in steep hills it will never be as capable as a comparable mid drive motor. Will it be as cheap as a hub motor'd bike? Probably not, but neither a BBS02 or TSDZ2 are what you would consider to be particularly expensive. If you are limited to buying a bike off the shelf... yeah sure its going to cost more. Maybe quite a bit more. But buying the bike you can afford is not the same thing as buying the right tool for the job. You can make do. You can settle - and there's nothing wrong with that. But you can't settle for less and make the case that you have not accepted a less-capable solution as a result.

There's a lot more to the why's and wherefores of this, but I'm trying not to repeat myself from earlier exchanges on the same subject.

If anyone wants a challenge: If you are in the Monterey Bay Area, Lets load our bikes up and don't pedal. Lets pick a hill. One would be Prescott Avenue, which is the widely-feared one. See which bike gets up the hill (remember, no pedaling. Only the bike is being tested). Preferably this is also a cargo bike challenge so we can both load up an equivalent amount of cargo... and see who either a) makes it up the hill and perhaps b) which bike survives the event without tearing out its nylon teeth inside the motor (both the BBSHD and Bafang hubs use equivalent gear material). I'll shut off my front hub motor so I don't have an unfair advantage. Or maybe I use a cargo bike that only has one motor to begin with.

But tests shouldn't be necessary as this is really a simple exercise in mechanics. A hub motor is single speed and it is out of its element on a hill - just like a poor human would be trying to ride a fixie on the same steep hill.

Everything has its place. Hub motors are great in many places. Make it a geared hub and that range becomes wider. But that range does not include 'everywhere'.

There is a lot on information being thrown around in this exchange, some accurate and some not. For instances there seems to be a misunderstanding of what battery voltage and Ah/Wh has to do with over all performance of a brushless electric motor system.

1. Voltage has to do with the maximum RPM the motor can spin based on it's windings. There is a rating call KV that translates into the RPM per volt applied to the motor. In such motors the ONLY way to increase the maximum RPM is to increase the voltage supplied to the motor.

2. The Ah/Wa a battery pack can provide can be compared to the number of gallons of gas in a car. The more Ah/Wh is the amount of energy stored in the battery for use by the motor to propel the e bike.

3. There are two other components that control the amount of work (torque) the motor can provide, they are the BMS (part of the battery pack) and the motor (speed) controller commonly known as the controller. The BMS is inplace to protect the battery from being over discharged (AMPS) as well low voltage cutoff, over voltage (charging) and balance charging of the battery pack.

NOTE: Th controller cannot draw more amps from the battery pack than the BMS allows, so you really need to know the limits of both the controller and BMS when setting up an e bike because if the controller is calling for more amps that the BMS's cut off setting the bike will shutdown.

To sum up I totally agree that the mid drive setup will out perform a hub motor of the same power rating because of the mechanical advantage of using the gearing at the rear wheel be it a derailleur or internal geared hub.

 

[ETrike]

To sum up I totally agree that the mid drive setup will out perform a hub motor of the same power rating because of the mechanical advantage of using the gearing at the rear wheel be it a derailleur or internal geared hub.

I would also argue that a good one from say Bosch will certainly outlast a hub motor if treated right given the current manufacturers of hub designs.

 

[Smaug]

<snip>

Video narrative is not technical, but does present some valid info:

I finally got around to watching this video. The guy is right on-point, as you say. He admits that he was biased at one point, but that a hub motor bike with torque sensor made him change his mind.

He decided hub motors are more reliable because mid drive are a lot more complex internally. I think it's more important to consider the reliability of the bike as a whole than to focus on the motor. I feel like a hub driven bike is more reliable not only because it is simpler, but because it doesn't put additional strain on the bicycle's drivetrain.

I do believe those who say a mid drive climbs better and is more efficient, but that is not to say that hub motor bikes CANNOT climb or are inefficient.

 

[munirider]

The reason I went with a mid drive was exactly about where I live. We live on a county road that climbs 1,750ft in eight miles from town to our home. It's not an even climb and the first section is 10% for a couple of miles. And that's not even the steepest I want to take it on some jeep roads around here that can climb four thousand feet in six or seven miles. I knew adding a motor to a bicycle drive would increase the wear and tear but wanted to have motor power through the range of gears. I would agree that a bicycle drive train is on the weak side for the kind of hp e- bikes have but it's what we have to work with. As soon as they make a multi speed hub motor I will get one even a two speed hi/lo range would be great.

That said if I lived in an area that was less hilly I would probably prefer a rear hub motor for ease of maintenance but I like the mountains

Other option of course is to have more than one e-bike, one for every purpose, I expect I will have several eventually but you gotta start somewhere.

 

[m@Robertson]

I think a lot of balderdash has obscured the original point of this thread: Which was to compare the performance of hub and mid drive motors in hills. this thread has gone WAAAAAY past that. My desire to never let a specious argument go unchallenged (and I am not lumping @Smaug into this statement) did not help restore clarity. My biggest concern with this sort of thing is what happens to the person who is completely green on the subject, and comes along after the fact looking for knowledge to help them through an expensive purchase ... and risks spending a pot of money on something that might work... but then again might not. Two thousand dollars too late.

With that said, I repeat my offer from many posts back which was more on-point to the intent of the thread:

... If you are in the Monterey Bay Area, Lets load our bikes up and don't pedal. Lets pick a hill. ... See which bike gets up the hill (remember, no pedaling. Only the bike is being tested). Preferably this is also a cargo bike challenge so we can both load up an equivalent amount of cargo... and see who either a) makes it up the hill and perhaps b) which bike survives the event ...

A bike can answer this question. Resoundingly.

 

[munirider]

Hub motors are great for a lot of reasons but they are not as good or better than mid drives for hill climbing. There's simply no argument, mid drives do hills better than hub motors, just a fact. Here's an example of what happens to hub motors when sustained and hill climbing https://ebikesforum.com/threads/who-knows-ebike-motors-hot-motor-pics.411

Whether or not there is more maintenance isn't the point, yea there's going to be more maintenance but so what. There's legitimate reasons for mid drives one of which is they are better for hills.