Quick questions about pedelec direct drive motors

[Zymosis]

Hey all. Longtime lurker, first post. Just to get that out of the way.

Long story short, I'm building up an ebike for my mom, which she'll be using for commuting ~10 miles each way. I've got a buddy who's helped point me in the right direction (crazy/amazing guy - calls his ebike the "deathbike" though I don't believe it's killed anyone...) but I still have a few questions regarding powertrain choices. I'd like to set the bike up as a clean build (minimal wiring and mounted stuff) and I'd like to go with a rear wheel direct drive hub motor that uses torque or cadence sensing - basically something that doesn't require a throttle and isn't a binary on/off. The Smart Pie 4 seems like a good option, except that it's not clear to me if/how it can be converted to pedal-assist. It seems like a hall effect sensor on the bb or chainring would only function as on/off, rather than proportional. In my perusing it looks like one method would be to run a CA3 and a torque sensing bb, but that would nearly double the price of motor. Is there a simpler/less expensive method of getting the proportional assist? Torque sensing bb straight to the Smart Pie - possible? At that point I'd be approaching the cost of a Falco unit, which (if I understand correctly) would already have all those features.

To sum it up, looking for...
- 300-400w direct drive rear hub motor
- integrated controller
- proportional torque/cadence sensing

So with that, I'd greatly appreciate any powertrain wisdom here.

Thanks!

 

[d8veh]

You haven't explained why you decided that the motor needs to be direct drive, which is heavy and fast, and needs a high power (heavy) battery. Is that what you want for your mom? If I built a bike for my mom, I'd use a a 48v Bafang BPM motor about 260 rpm (code 14) with one of these batteries that have a 20A sine-wave controller included. This kit will weigh about half of a Smart Pie one, but it'll have more torque. DD motors are great for continuous high-speed on flat roads. Geared motors beat them in just about any other situation.

http://www.bmsbattery.com/battery-pack/701-bottle-ebike-battery.html

http://www.bmsbattery.com/ebike-kits/586-bafang-350watts500watts-bpm-motor-e-bike-kit.html

 

[cycborg]

I do a 10 mile commute on a 750 W Bafang BBS02 mid-drive. Although this apparently means I don't qualify as a grownup (I suppose my wife and teenagers would agree, at least on occasion), my experience might be useful to you.

The commute takes about 30 minutes. Most of the time I'm running at about 450 W, and my speeds are mostly 20-25 mph. The controller implements cadence-based PAS. This doesn't feel as natural as torque-based PAS (I assume; never actually used torque-based), but at least with my system it doesn't take too long to get the hang of it. The trickiest part is interrupting the motor output to change gears, but this isn't an issue with a hub drive.

For system size and ease of setup/use, I'd say d8veh's recommendations look good. Reliability of the gearhub vs. DD is a consideration since the gears tend to wear out over time, but probably not an issue with light use. They're also noisier. But the reduction in weight is nice. The torque/speed tradeoff is something you'll have to judge for yourself.

The battery/controller linked by d8veh says it uses a torque-sensing BB, but from the photo it definitely looks like a cadence sensor. If it matters to you, I'd contact them for verification.

 

[Zymosis]

Thanks so much for all the replies.

To answer the big question, no, I'm not overly attached to a dd hub motor. Some very ebike savvy friends have pointed me in that direction but I feel like I have a grasp on the other options (mid drive, geared, etc). More than anything I'm looking for an effective system that has slick integration (controller in particular) because I don't want this bike to feel like a science project when I give it to my mom.

The thought of a BBS01 mid drive kit is certainly an interesting option - looks like the controller is all integrated. One thing that was originally appealing was the thought of running a rear nuvinci with Gates drive (back when I was considering front hubs, which I'm trying to avoid now), which would be great with the mid drive kit. But I've read that you're not supposed to run PAS on igh's - can someone elaborate on why not? Cause that seems would be a great solution...

A geared hub motor is certainly an option that I've considered, I just didn't want anything that was super loud or prone to needing service. D8veh's battery with integrated controller was pretty neat though I was hoping to with a rack mount battery. Did a bit of browsing and didn't see any rear rack batteries that have integrated sine controllers - are they out there?

 

[Zymosis]

After giving this a bit of thought, and riding a few off-the-shelf ebikes locally, I think I have a plan. After riding a cadence-sensing bike I'm afraid that might be an intimidating power delivery compared to the torque-sensing, which was smoother as expected. I think a small geared rear hub makes the most sense. As far as "slickness" per my previous posts... ditching that requirement moving forward.

Q100H rear hub motor with derailleur setup
Controller TBD, but one with very good torque sensing
Bottom bracket torque sensor?
Half-grip throttle

The big questionmark now is the controller. Is there a particular controller that is known for having the smoothest/best torque-sensing power delivery? Are there any Q100H-friendly controllers that would deliver a riding experience (power delivery wise, at least) to a Bosch mid-drive system? The one Bosch bike I rode had incredibly smooth torque assist, very fluid. If there's a Q100H controller that could provide a similarly unobtrusive riding experience, that would be the ideal.

 

[friendly1uk]

Do you realise the simple controllers like the 890 have 3 speed targets. Plus the walk speed button. They all use full power to reach their targets, but it's not exactly frightening levels of power. She could start by using the walk button. It takes off strongly then stops at walking speed. by which time you have barely moved, and it's easy to get over the shock. Remember it's walking speed, she's not going anywhere. Then she can expect the same, but through till 7 mph on level one. Any slower and she might fall off. At these speeds I don't think full power is going to take her by surprise. Build it legal and she will be fine. Later you can think about delimiting. A softly softly approach is the safest, but I don't think the lack of a comparatively expensive torque sensor should be an issue.

The S series can have that speed target, or a power level choice. You may be able to set that choice with an lcd1 then fit a simple led meter.

 

[amberwolf]

The distance seems long so to be handled by a bicycle, and therefore for such a distance an ebike is not a good idea.
For a grownup an electric scooter at 48V is an more wiser selection, he / she will be able to load and few shopping bags to it.

Well, I guess all us little kids ought to get off our long-distance bikes and stay home.

Maybe you ought to look around and see what people actually do, instead of only telling people what to do based on what is likely your own methods of doing things, instead of what is actually possible?

Take a good look around just *this* forum, and you'll see quite a few that ride more than 10 miles at a time.

Some of us do 30 miles, or 50, or 100! Oh, my gosh! Such children we are.


I don't suppose you've ever looked around at the world's various cities and towns, and rural areas, and noticed that in a fair number of places, it's more than 10 miles from where people live to where they want/need to go? And that a fair number of them actually do ride just plain old bicycles that far, and much farther, regularly? (before my knees started going bad, that's all I did, was bicycle, no ebike stuff...for distances easily that far even in Phoenix AZ weather.)



Really, all I want you to do is open your mind to the possiblities out there, before you condemn what others already do, and before you give what is probably bad advice to people that came here for help. :/



To the OP: Apologies for the OT; I am afraid I don't have any specific advice for your problem, except that as others have said, a geared hub rather than DD is probably a better option, and as has been pointed out, some controllers ahve multiple speeds (and/or power levels) for the assist. The Fusin 1000W kit I reviewed in that section of the forum and later used on Delta Tripper has both PAS and throttle, but you can use just one or the other to control it, and it has several power levels to choose from. I'm sure ther'se a lot of them out there like that nowadays.

 

[friendly1uk]

I had missed that. 20 miles is nothing. In fact, it is within range of the shortest range bikes you can buy.

 

[wineboyrider]

It's kind of nice to read a thread about a real electric bicycle and not a moped or motorcycle type thread, actually. Ebikes at bicycle speeds is what the vast majority of the world really wants/needs. 8)

 

[Zymosis]

Do you realise the simple controllers like the 890 have 3 speed targets. Plus the walk speed button. They all use full power to reach their targets, but it's not exactly frightening levels of power. She could start by using the walk button. It takes off strongly then stops at walking speed. by which time you have barely moved, and it's easy to get over the shock. Remember it's walking speed, she's not going anywhere. Then she can expect the same, but through till 7 mph on level one. Any slower and she might fall off. At these speeds I don't think full power is going to take her by surprise. Build it legal and she will be fine. Later you can think about delimiting. A softly softly approach is the safest, but I don't think the lack of a comparatively expensive torque sensor should be an issue.

The S series can have that speed target, or a power level choice. You may be able to set that choice with an lcd1 then fit a simple led meter.

Could you elaborate on what you mean with respect to 3 speed targets? Do you mean that, if I set it at PAS Level 1, it will essentially deliver power like a step function, with 3 steps that correlate to different speeds? Just not clear on exactly what you're describing on a practical level. I think I can say with confidence, however, that I'd prefer to avoid anything that delivers full power with minimal torque/pedal input.

I know there are a number of torque sensing bb's out there - what sort of controller would those integrate with? Or rather, what would be the best way to integrate one of those with the small geared hub motor for the smoothest true torque-based power delivery? Really aiming for Bosch-like slickness of torque sensing, if possible. I hate to say it, but the Falco units are starting to sound more appealing...

 

[d8veh]

It can be quite complicated depending on which controller you get.

Most controllers have speed control algorithms in their software, so the different throttle positions represent target speeds. Generally, the further you are from that target speed (below it), the more current the controller gives in an attempt to reach it. There's all sorts of other effects too from the motor, which reduces the current towards the top end of the speed range, so as well as the controller tapering down the power, the motor reduces it too.

The different PAS levels correspond to fixed throttle positions, so they work like a cruise control.

The S and P series controllers from BMSB have a setting, where you can change the algorithms from speed targets to current targets, so in current control mode, which they call "torque simulation mode", you get constant current at a different level with each PAS level.

IMHO, current control works much better for crank-drive motors, where it's necessary, but doesn't offer much for a low-powered hub-motor apart from reducing the initial torque surge.

 

[Htfan]

Very glad to have found this post! I've been researching to find out how to implement the "current type PAS" you described below. I have a 12 fet Lyen Controller and installed the 3 speed switch and have been experimenting with different settings but not getting the functionality I'm looking for.

My old low end controller provided 3 levels of current control PAS (low= 5a, med= 9a and high= 18a). This worked well for my needs. It has been suggested, but afraid a CA3 is cost prohibitive at the moment.

Any recommendations are appreciated!

... The S and P series controllers from BMSB have a setting, where you can change the algorithms from speed targets to current targets, so in current control mode, which they call "torque simulation mode", you get constant current at a different level with each PAS level.

IMHO, current control works much better for crank-drive motors, where it's necessary, but doesn't offer much for a low-powered hub-motor apart from reducing the initial torque surge.

 

[Htfan]

I'll answer my own question...

Decided to try the voltage type PAS to see if that will provide the "current controlled" type pedal assist functionality I'm looking for. I'll keep you posted with my findings.

 

[crea2k]

My vote is a Bafang bbs2 and a geared hub, easy, low maintenance, smooth gears etc.

 

[Zymosis]

I got out from the same river of thoughts by selecting a modern controller system with display and 9 Pass levels available.
Also all those 9 Pass levels are fully customizable by the user, just by selecting the settings of your preference by using the display controller that comes with it.
I am 100% convinced that only such a setup, it can replace the need for torque-based power delivery.
The only lets say drawback is that the very detailed settings will assist only the driver and owner of this bicycle.
Which in my case is not a problem.

Which controller did you end up using?

 

[Zymosis]

My vote is a Bafang bbs2 and a geared hub, easy, low maintenance, smooth gears etc.

I'm actually starting to lean back towards a bbs01 for my mom's bike. Paired with an igh, it seems like a pretty slick system. No external controller, integrated pas, basically plug-and-play. I think I'm at 80%. Gotta decide asap...

 

[crea2k]

Yes, this is why I might be putting one on a second, cheaper project bike, as its an all in one solution, the only other thing you need is batteries or as an extra a gearless hub.

 

[MadRhino]

You don't say much about your mom.

How old is she, and what is her physical condition.
Does she ride this commute on a pedal bike already.
What is her biking experience and skill.

Those simple facts are essential in the choice of appropriate type of eike that she will like to ride.

 

[Zymosis]

You don't say much about your mom.

How old is she, and what is her physical condition.
Does she ride this commute on a pedal bike already.
What is her biking experience and skill.

Those simple facts are essential in the choice of appropriate type of eike that she will like to ride.

Near 60, good hiking shape but currently suffering from an ankle tendon injury due to over-use. My parents' idea of an after-dinner hike is 10 miles up and down a mountain. She doesn't currently ride this commute because of the distance but has been considering an ebike to make it an easier physical experience. I'd rate her biking ability as casual/occasional rider, mostly short around-town stuff unless she's on the tandem with my dad.

I've noticed a pretty big price variation in the BBS01 kits, from ~$350 up to ~$650. I was leaning towards buying the EM3EV kit as it's not the most expensive and seems to be reputable on es. Can anyone shed some insight into some of the differences between kits? Seems like a pretty big delta...

 

[MadRhino]

If budget is tight, you can build with a cheap 250w pedelec kit on a cruiser type geometry. Personally, in this situation I would go for the 350w Bionix on a long wheelbase FS bike, but that is a very different expanse of time and money.

 

[Zymosis]

Fyi, the frame is going to be one of these:
http://www.shopcalfee.com/1-booganda-bikes/

Long story, but this bike is actually being built up as part of a work trade, so hence the bamboo frame.

Still leaning towards getting a BBS01 kit from Em3ev...

 

[MadRhino]

Fyi, the frame is going to be one of these:
http://www.shopcalfee.com/1-booganda-bikes/

Long story, but this bike is actually being built up as part of a work trade, so hence the bamboo frame.

I hope your mom is short. They make nice bamboo frames but I see nothing there longer than 48cm !
I guess they target the kid's bike market, or they believe in Uganda that the rest of the world is either short or extra short.

 

[Zymosis]

Fyi, the frame is going to be one of these:
http://www.shopcalfee.com/1-booganda-bikes/

Long story, but this bike is actually being built up as part of a work trade, so hence the bamboo frame.

I hope your mom is short. They make nice bamboo frames but I see nothing there longer than 48cm !
I guess they target the kid's bike market, or they believe in Uganda that the rest of the world is either short or extra short.

There's a wider variety of frames than you see there, but that gives the general idea. Unbeknownst to her, she's actually going to get fitted at the shop to help with frame selection.

Kiriakos, thanks for reminding me that the decisions are mine - but that doesn't mean I have to like it! It's always scary to me, buying things in a market with so many different and unique options...