A note on hub motors for hill climbing

[arthurdent18610]

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. They're 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.

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.

I have both a hub & mid drive, the hub is a 250/1000w, the 250w being the legal power output for uk roads, max speed 15.5 mph. The mid drive is a bafang 750w, currently broken, stator & rotor burnt out. I prefer the simplicity of the rear hub & have no problems climbing hills with the seven speed freewheel. The hub is easier to work on & is half the price to replace, I've seen cheaper rear hubs, but my current model has covered 10,000 miles without any issues, its 8 yrs old & cost £150 back in 2015. The bafang cost me £360 back in 2021& is going to cost me £160 to fix & had only covered a tenth of the milage of the hub when it broke. I also like the way the power comes in on the hub, thump throttle & PAS fitted. The bafang was fun, but it'll end up being sold or given away for parts.

 

[sojourner]

Two more considerations. Pedal only bikes, when ridden substantial distances, are ridden by experienced cyclists. Not the case with ebikes. I recall this gent walking his loaded bike home....7 miles, for want of a chain tool.
Hub motors are NOT effected by frame ridgidity to the extent mid-drives are. A mid-drive step through is problematic.

 

[m@Robertson]

Hub motors are NOT effected by frame ridgidity to the extent mid-drives are.

That is only true when we are talking about a super powerful mid drive pulling like hell on the rear triangle of a full suspension bike. So you pick a frame that has a strong rear suspension linkage. It won't require a lot of added care. My most recent build used a frame from 1999.

But powerful hub motors require reinforcement as well. Just a different type. A hub motor with less power than a typical Bafang mid drive (80 Nm, 52v and a 35a controller) needs torque arms to keep it from destroying either a fork or a frame dropout.

Speaking as someone who has learned this the hard way (two torque arms not sufficiently tight or well-designed, which I learned too late, permanently destroyed a fork) torque arms are an important part of a hub motor build. The arms are on both sides on the front and just one on the back:

A mid-drive step through is problematic.

Only if the frame was not designed for a mid drive in the first place. Otherwise step-thru mids are manufactured in wide variety and work just fine. To be fair, the Sondors bikes are sold with weak drivetrains, but that is the manufacturer cutting corners (7 spd freewheel... not a cassette!) and not the platform's fault.

The Serial 1 (Harley-Davidson) isn't exactly low-quality engineering, right?

EDIT: All of the above notwithstanding, I don't want to give the impression that mid drives are simple to build. I've said before that it is pretty easy to build a hub drive bike, and this is echoed generally in the DIY community. There are a lot fewer details that have to be paid attention to. To build a mid drive bike, the builder has to know what they are doing. And do the work.

And if it hasn't been said enough times already, there is nothing wrong with either approach. They are two choices along a spectrum, with each being ideal in a different part of same, with some overlap.

 

[JerryB]

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.

Just adding my two cents......sorry if your feathers got ruffled.

 

[m@Robertson]

Just adding my two cents......sorry if your feathers got ruffled.

They weren't in the least. If I gave that impression I didn't mean to. The discussion was about a parameter in a test, not rider preference and I was focusing on that topic.

 

[kmccune]

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.

I think some of these guys have pretty stout gearing internally as well? You let that armature move a little and its game on, a little slack lets that bugger go.The old humble direct drive can only use its battery and controller for its"transmission" so to speak, thats the beauty its usually adequate,for some apps, you need the torque multiplication of a cogset plus the internal reduction.
It did Me good to see the drag racers move from Libertys and crashboxes to "Powerglides" and sometimes direct oupling when engine management and power caught up.I liked to watch this beautiful street legal camaro( with a powerglide transmission"on E85") consistently run in the sevens.Gearing is important, usually it compensates for deficiencies in other areas. Excuse me "A" this answer has some relevance to the thread, "Gearing, gearing" not trying to jack a threasd.

 

[kmccune]

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.

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.

Finally, my computer needs to go the great recycle bin-Anyhow,yes! Tech will catchup, flashes in the pan" like ceramic cassette will gradually go to the "museum of WTF, what was I thinking at the time" while the motor tech will get better and better,I could see the motor and transmission inttergrate in a swing arm assembly, just for the room to put stuff in there if the handling and CG could be addressed.At the end of the day due to the advantages of gearing middrive trumps low speed and max effort riding.
We are constrained by a couple of factors , limits to motor power( the Nazis are watching) weight, endurance( only going to get better as battery tech catches up) ease of maintenance( are you silly?- they want you to have to keep buying their wares) besides the shops and factory reps want to be 'gurus" only exceptions I know of are Ravi and maybe Justin.
Perhaps one day recycling will play a larger role in design, while more outstanding and better tech makes the 'Hub Drive experience " better, its already good enough for Me because of my rough and steep riding skills or lack thereof. When I stall a Hubdrive ,I am usually in crash mode, so for a bloke like myself its already good enough .Forget the HP wars be happy and ride( was impressed by the torque of a 36 volt 350 watt unit once) Shalom!

 

[James340]

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).

View attachment 8796

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

View attachment 8797

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

View attachment 8798

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.
View attachment 8799

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

This is a old post but I am trying to determine if I can put a 1000w front hub motor on a 1990's MASI road bike I have.I see how massive the front forks are on your bike.I plan to make custom torque arms that are full length of the fork& preloaded tension.Do you think the smaller forks of a road bike with torque arms will be okay? Thank you for your time

 

[m@Robertson]

This is a old post but I am trying to determine if I can put a 1000w front hub motor on a 1990's MASI road bike I have.I see how massive the front forks are on your bike.I plan to make custom torque arms that are full length of the fork& preloaded tension.Do you think the smaller forks of a road bike with torque arms will be okay? Thank you for your time

No I would never try that I'm familiar with Masi from back in the day. The only successful builds I have seen for an old school road bike are the ones that used a BBS02, and toned the power down so it was very gentle on its pull on the rear triangle at startup, ramped up power slow and kept it low at full cadence. Consider that a front motor not only pulls the fork blades and stresses the dropouts, it also exerts stress on the headset. For the first couple of 2wd bikes I built, which were short-wheelbase bikes, I used a doubled up star nut to keep the headset from loosening within a ride or three.

Your long torque arms will just transfer the failure point up higher in my opinion. Do I have experience with this? No but I think there is absolutely zero chance it would ever work. Its too far outside the envelope for a road bike frame.

Another potentially successful build method would be a TSDZ2 that has been similarly de-fanged. I know a custom builder in Northern California who does this sort of thing all the time with low power 36v setups but you would need to know the ins and outs of the Tongsheng motor which is nowhere near as widely documented as the BBSxx.

 

[James340]

No I would never try that I'm familiar with Masi from back in the day. The only successful builds I have seen for an old school road bike are the ones that used a BBS02, and toned the power down so it was very gentle on its pull on the rear triangle at startup, ramped up power slow and kept it low at full cadence. Consider that a front motor not only pulls the fork blades and stresses the dropouts, it also exerts stress on the headset. For the first couple of 2wd bikes I built, which were short-wheelbase bikes, I used a doubled up star nut to keep the headset from loosening within a ride or three.

Your long torque arms will just transfer the failure point up higher in my opinion. Do I have experience with this? No but I think there is absolutely zero chance it would ever work. Its too far outside the envelope for a road bike frame.

Another potentially successful build method would be a TSDZ2 that has been similarly de-fanged. I know a custom builder in Northern California who does this sort of thing all the time with low power 36v setups but you would need to know the ins and outs of the Tongsheng motor which is nowhere near as widely documented as the BBSxx.

Thank you for the information

 

[kmccune]

Beware of the cheap Ecycle, a few good headers and face plants made Me a lot more cognizant of my own fragility and the design limits of cheap bicycles.
Taking the 'loop' the other day I realized the trailbikes had destroyed it and I found myself dismounting and walking the bike through the "anklebreakers" and dislodged rocks, these days my scars are deep and purple, kind of like the epipheny I had when doing very dangerous things, my limbs and senses are still intact, time to quit, I may have 20 years left If I am careful so never think it will not happen to you, too many Guys younger than I am are leaving this 'mortal plane".

 

[JerryB]

Speaking of hills...

.

I still remember my childhood fondly, when my dad used to roll us down the hill inside car tires.​

Those were the Good Years.

 

[Wiley]

No not at all. Both hubs and mids can have throttles.

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.

I don't know if you are aware of this but Bafang mid-Motors have a controller that can be reprogrammed so Throttle cut out can be made higher.
Usually they cut out based on the PAS 2 (?) Speed limit. But you can change it so it has unlimited speed, by uncoupling it from PAS levels and bypassing any limits.
You can also change speed ranges for Each PAS level.

 

[m@Robertson]

I don't know if you are aware of this but Bafang mid-Motors have a controller that can be reprogrammed so Throttle cut out can be made higher.
Usually they cut out based on the PAS 2 (?) Speed limit. But you can change it so it has unlimited speed, by uncoupling it from PAS levels and bypassing any limits.
You can also change speed ranges for Each PAS level.

I have written multiple articles on how to dig in to every aspect of those motors' settings. Here is the most recent:

BBSHD Programming For The Pedaling Cyclist (2023 Update)

Explore enhanced BBSHD programming for pedal assist settings that don't let the bike run away from you, and throttle settings gentle on the drivetrain.

talesontwowheels.com

I have never seen any Bafang mid drive whose throttle is set to limit at PAS2. Every one I have ever seen is sold with throttle set to PAS9 as its upper limit. In turn PAS9 is typically set to '100' on both Speed and Current, so throttle is by default max motor output. It is of course possible that a reseller changes this, but I've never seen it or heard anyone say theirs was set that way. Usually the way a seller limits the motor is via the current limit setting, which is global.

Plus, since the Designated Assist Level is either PAS 1 through 9, or By Display Command, which in turn is also a PAS level setting, you don't give a throttle unlimited power by decoupling it from PAS, because you can't. Instead you have to do it as described above.

The way you unlock the speed limit on throttle on such a bike - assuming its a throttle-only limit - is to simply set the Throttle Speed Limit to the limit you want on the dropdown, or set it to By Display's Command, and then lift the limit on the display's settings. Usually thats the way people go.

 

[Hoggdoc]

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

How about sharing your sources for your latest upgrade?

 

[HumanPerson]

How about sharing your sources for your latest upgrade?

Absolutely

That stuff isnt on the Aventon Aventure anymore, i've put that back stock except for the added dual battery discharge balancer.
This stuff is on the mongoose hitch now.

https://www.e-streetbikes.store/product-page/2000w-sabvoton-fat-tire-motor-kit

(pretty sure this is 1800w not 2000w but who knows)

Amazon.com

Ebike Battery 72V 60V 52V 48V Lithium L-ion/Lifepo4 20AH/30Ah/35A/40AH/50A/60A | eBay

Find many great new & used options and get the best deals for Ebike Battery 72V 60V 52V 48V Lithium L-ion/Lifepo4 20AH/30Ah/35A/40AH/50A/60A at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Hoggdoc]

Absolutely

That stuff isnt on the Aventon Aventure anymore, i've put that back stock except for the added dual battery discharge balancer.
This stuff is on the mongoose hitch now.

https://www.e-streetbikes.store/product-page/2000w-sabvoton-fat-tire-motor-kit

(pretty sure this is 1800w not 2000w but who knows)

Amazon.com

Ebike Battery 72V 60V 52V 48V Lithium L-ion/Lifepo4 20AH/30Ah/35A/40AH/50A/60A | eBay

Find many great new & used options and get the best deals for Ebike Battery 72V 60V 52V 48V Lithium L-ion/Lifepo4 20AH/30Ah/35A/40AH/50A/60A at the best online prices at eBay! Free shipping for many products!

www.ebay.com

OK thanks that looks like a direct drive system.

 

[HumanPerson]

OK thanks that looks like a direct drive system.

Yeppers. It's pretty simple, ya can just dump a ton of amps through it lol

 

[Hoggdoc]

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.

There are a number of internally geared multi ratio hubs available on todays market. But be care a some are not really rated for the power a high power mid drive motors can provide.

 

[Hoggdoc]

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.

Note to anyone wanting to try the link in this post, it takes you to a post talking about mirrors for ebikes.