Advice for Lightweight PAS Commuter - Friction vs Hub Motor

[Neskie]

Hi ES Forums!

I'm a new member and a newbie to the E-bike world. I've been doing quite a bit of research on this forum for the last few weeks to get prepared for my first ebike build (fantastic forum, btw). But I'm now at the point that I could use some direct advice. Here's my story:

Desired Specs;
Range: 20 miles (maybe 40 miles for round trip, but unlikely)
Nominal Speed: 20mph (32kph)
Expected top speed: ~25mph (40kph)
Total weight/load: ~200lbs (90kg)
Budget: ~$700

I'm an avid cyclist and commuter, so I've never felt a need for an assisted bike. However, I recently changed jobs and my commute is now ~20mi (32km). I don't mind the mileage much, but unfortunately the extra time is just eating through all my free time. I can average ~15mph comfortably with good weather. What I would like out of a Pedal Assist build is to bump that average speed up to ~20mph and maybe a tad higher (25mph max speed?), so I can get my commute time down to about 1hr. Also, it wouldn't hurt to cut down on the day-to-day exertion if the weather is not great or I'm just feeling lazy . However, my route has very little elevation (Minnesota +1), and I don't mind pedaling at startups and putting down about equal power to the motor. I'm also somewhat light at 160 lbs and a ~30lb loaded bike. So I'm thinking I can get away with a pretty low power system.

My current ride that I'd like to convert over to pedal assist is a steel-frame, cyclocross bike with drop bars and disc brakes (pictures to follow). I have road tires (gatorskins 700c x 25mm) to make it a bit quicker. I'm also running it single speed with Gates Carbon Belt drive. This limits my rear wheel options, and I'll probably have to change the gear ratio once I finalize my ebike setup. It's been a great, limited-maintenance, year-round commuter for me, and handles my pannier loads quite well. You can tell I'm a little smitten

Ideally I'd like to put together a lightweight kit (~5kg). But more importantly, I'd really like to retain the functionality of my commuter as an unassisted bike by taking the kit on/off on at least a weekly basis. That's primarily what has led me to research friction drives. They seem pretty ideal with a couple major exceptions: 1) the commercially available options are pricey and 2) I'm not sure if they can be run in rain or snow.

So here's what I've come up with so far:

PLAN A - Friction drive options
a1) Add-E
- This seems to be the most polished commercially available system. The only problem being the price. $1200 USD is just a bit to high for my budget considering other options
a2) Go-E
- This seems to be the same design as the Add-E but at a much more reasonable price. Only problem being it's not available in USA (yet)
a3) Kepler's Mid-Drive
- Seems like a great design and I would much rather support the ES community (especially given Kepler's signification contributions). Unfortunately, it looks like he's moved on to other projects
a4) Adrian's Commuter Booster
- Also a great ES forum designer and a well put together website. Unfortunately, it also looks like he's also no longer supporting this design
a5) Velological Velospeeder
- This is my favorite concept so far. Unfortunately, it doesn't seem to be very well developed yet and definitely not available in the USA


"The Morning After Plan" - proven, less expensive than the alternatives, readily available ... you know ... The Hub Motor
b1) Qute 100 Front
- So far it's the best balance between cost and weight I can find. I'd use a front because of the possible tricky gearing with the belt drive.
b2) GoldenMotor Smart Pie
- More expensive than Q100 but I like the idea of having an integrated controller. I'm thinking it would make things much easier when switching between the hub motor and my regular wheel
b3) 8Fun 250W Front (from Leed e-bike kits)
- Probably not the lightest hub, but I like the US shipping and support


Battery Options:
I've been debating between LiPo and LiIon (18560-cell) chemistry. Right now I'm leaning heavily towards Li-Ion for the sake of stability and idiot-proofness. Especially since I've never worked with LiPo. Right now, I'm thinking of going with 24V10ah if I can find a friction drive. Or if I go with the hub motor, I think I'll need 36V10ah or even 48V10ah depending on the RPM of the motor. I'm approximating that it will take around 350Whr to get me to my 20mi range with some extra margin (assuming I can get ~16 Wh/mi efficieny while pedaling) . I'll just have to bring the charger to work with me I suppose


So thanks for reading and making it this far

If you have any suggestions or experiences to share, I would greatly appreciate the posts. Specifically, if anyone knows where I could get a Friction Drive mechanical assembly shipped to the USA. Also, I would appreciate if anyone has any recommendations for which make/model of lightweight (low power) front hub.

Thanks!

 

[motomech]

I can average ~15mph comfortably with good weather. What I would like out of a Pedal Assist build is to bump that average speed up to ~20mph and maybe a tad higher (25mph max speed?), so I can get my commute time down to about 1hr. Also, it wouldn't hurt to cut down on the day-to-day exertion if the weather is not great...

The references to the weather implies rain
Having no experience w/ friction drives, I'm not sure how they would work in the wet, I have read, not very well.

As for batteries, I'm not pushing Lipo, but there is a relatively new line that seems to be designed for low-powered Ebikes, the Multistars;
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?idCategory=1388&LiPoConfig=6&sortlist=H&CatSortOrder=desc
With their 10C discharge rate, they are not suited to high-powered systems, but are fine for something like a Q100.
Of particular interest to us, are their large capacity bricks, 5800 mAh, 6600 mAh, 8000 mAh and even 10,000 mAh. If the large form factor bricks can be fitted into the space of your build, they allow lots of capacity, while keeping the packs simple(2P). 2P Lipo packs are fairly easy to build and maintain.
When the Multistars first came out, HK was offering great deals on discounted bricks, rotating thru the various sizes. But now selection is limited and the discounts are not so common. No doubt due to their popularity. In time, they will be restocked and there will be joy again on Lipo street. I bought 4) 6S/10 Ah bricks on sale for $230 shipped. About a 40 mile range @ 20 mph on my bike. No other battery comes close to that range/cost value that I'm aware of.
Lipo also offers more versatility in placement of the bricks.

If Li-Ion remains your prefered chemistry, you might want to check out Luna Cycles. They have recently expanded their line-up. Something for everybody.
http://lunacycle.com/batteries/packs/

 

[Neskie]

Hi momotech,

Yes, I'm planning on using the friction drive in rain and possibly even snow (overconfident, I know ) ... I've read conflicting reviews on if they work in with rain, so I was just planning on trying first hand for myself. However, I know the hub motor would be the best "all around" for my applications.

Thanks for your suggestions on LiPo. It does look like there are still some discounted Multistar 6S 5200mah packs. I think I could use 2 of those paralleled to get my 20mi and expand up to 4 paralleled packs if needed.

I have one major LiPo newb question though: On ebike applications, how do you limit the discharge of the batteries to 80% of their total capacity? From what I've read, this seems very important for both safety and longevity of the batteries. However, it doesn't seem like any of the motor controllers (either FET-based or RC/ESC) have that capability. Do I then need another control component like the Cycle Analyst?

 

[motomech]

I have one major LiPo newb question though: On ebike applications, how do you limit the discharge of the batteries to 80% of their total capacity? From what I've read, this seems very important for both safety and longevity of the batteries. However, it doesn't seem like any of the motor controllers (either FET-based or RC/ESC) have that capability. Do I then need another control component like the Cycle Analyst?

I believe the 80% rule extends battery service life, but as to how much, it's difficult to say without long-term testing.
The frt.part of my battery usage is always the same. First charge after a ride is to a store (cell) voltage, 3.80 to 3.90V.
10 or 15 minutes before I go out on the next ride, I will top off to 4.00V to 4.10V. It doesn't take long, even on my 20 Ah pack, as I have a really fast bulk charger.
Since I have a large capacity, range and discharge values are usually not a concern. But if the distance requires it, I monitor the pack with a simple mini-voltmeter. I know the battery values are supposed to be calculated with a Watt/hr formula, but I have been doing this long enough to know, for my bike and riding style, I will always get between 1 1/2 to 2 miles per Ah.
Voltage wise, for a 12S/1P pack, about 1 1/2 miles/Volt. So, for 12S starting out @ 49V and hitting my LVC @ 42, I can go 10 miles. For my 4P pack, between 30 and 40 miles.
In real world riding, I don't even calculate that. I simply know when I reach one half of my dis-charge Voltage range (45.5V), it's time to turn around and head for home.
All very simple, which is good, because I have no idea what the second half of your question is referring to.
Bear in mind, I have 2WD w/ another 5Ah to 10Ah pack.
Big battery capacity makes sticking to the 80% rule easy and Lipo makes carrying lot's of capacity easy as well.

 

[Neskie]

I believe the 80% rule extends battery service life, but as to how much, it's difficult to say without long-term testing.
The frt.part of my battery usage is always the same. First charge after a ride is to a store (cell) voltage, 3.80 to 3.90V.
10 or 15 minutes before I go out on the next ride, I will top off to 4.00V to 4.10V. It doesn't take long, even on my 20 Ah pack, as I have a really fast bulk charger.
Since I have a large capacity, range and discharge values are usually not a concern. But if the distance requires it, I monitor the pack with a simple mini-voltmeter. I know the battery values are supposed to be calculated with a Watt/hr formula, but I have been doing this long enough to know, for my bike and riding style, I will always get between 1 1/2 to 2 miles per Ah.
Voltage wise, for a 12S/1P pack, about 1 1/2 miles/Volt. So, for 12S starting out @ 49V and hitting my LVC @ 42, I can go 10 miles. For my 4P pack, between 30 and 40 miles.
In real world riding, I don't even calculate that. I simply know when I reach one half of my dis-charge Voltage range (45.5V), it's time to turn around and head for home.
All very simple, which is good, because I have no idea what the second half of your question is referring to.
Bear in mind, I have 2WD w/ another 5Ah to 10Ah pack.
Big battery capacity makes sticking to the 80% rule easy and Lipo makes carrying lot's of capacity easy as well.

Thanks for the sharing, Momotech! I think you definitely answered my questions. I was looking for how to monitor the LiPo pack % during riding and how important it was to battery life and safety. It sounds like you primarily used a voltage meter, which Hobby King stocks plenty of. I also see that after doing a few trips, I'll probably have a good idea to what my mileage per volt will be.

So, I've been researching the heck out of them over the last week or two. In fact, I was just about to pull the trigger on the Turnigy Multistar packs.

However, just today, I found a 24V @ 10ah Li-Ion pack through ELifeBikes for $90 USD. When factoring the shipping, charger, and power supply costs, the two packs come out relatively even on pricing and even weight (to my surprise). The major difference I can see is the discharge rate - 10C for LiPo, ~1.5C for Li-Ion. I'm hoping the 1.5C might still be enough for my low-power setup. Unfortunately, I can't find any reviews of the Elifepack that I'm interested in. Here's the link for reference:
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2014-6G-2E9X.86KSU

Any suggestions?

I should also mention that a possible added bonus to the 24V Li-Ion pack might be that I won't have to modify the motor controller (6FET 350W) to handle the lower voltage of the 6S LiPo pack. It would be a simple resistor change, but still, my soldering skills are a little rusty

 

[Kepler]

- Seems like a great design and I would much rather support the ES community (especially given Kepler's signification contributions). Unfortunately, it looks like he's moved on to other projects

Are you talking about my Mid drive "Single Track Weapon" or my recently completed ultra lightweight friction drive project?

If you are cyclist who really wants an ebike that pedals like a roadbike, my last build may be of interest to you.
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

[youtube]Miy1V0YjwBQ[/youtube]

 

[motomech]

Thanks for the sharing, Momotech! I think you definitely answered my questions. I was looking for how to monitor the LiPo pack % during riding and how important it was to battery life and safety. It sounds like you primarily used a voltage meter, which Hobby King stocks plenty of. I also see that after doing a few trips, I'll probably have a good idea to what my mileage per volt will be.

So, I've been researching the heck out of them over the last week or two. In fact, I was just about to pull the trigger on the Turnigy Multistar packs.

However, just today, I found a 24V @ 10ah Li-Ion pack through ELifeBikes for $90 USD. When factoring the shipping, charger, and power supply costs, the two packs come out relatively even on pricing and even weight (to my surprise). The major difference I can see is the discharge rate - 10C for LiPo, ~1.5C for Li-Ion. I'm hoping the 1.5C might still be enough for my low-power setup. Unfortunately, I can't find any reviews of the Elifepack that I'm interested in. Here's the link for reference:
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2014-6G-2E9X.86KSU

Any suggestions?

I'm afraid you have lost me here.
I like elifebike and use their controllers, but never their batteries. Headways, I.M.O., are outdated and the heaviest form factor of Lithium. Why would you want 13 Lb. boat anchor that only supplies 240 Wh's of capacity? That amount of Lipo would weigh about 1 1/2 lb.s.
But then again, I'm unsure why you are stuck on 24 Volts. The first step in designing a system is to match the Voltage(system speed) to the desired road speed while keeping the motor speed/whl. size in it's efficient range. Even using a high speed mini, like the Q100 328 in a 700 cc wheel(a poor combo for efficiency), the top speed would only be 16 mph.

A mid-speed mini, like the Q100 (260) for example, in a 700cc whl., run @ 36V, would have a useful top speed of 21 mph.
I used the run this motor @ 9S in order to match the 31 V LVC of my ELB controller and found it to be a nice low-powered system with a top speed of 19 to 20 mph. That's about the lowest Voltage that I feel is practical.

 

[Neskie]

Are you talking about my Mid drive "Single Track Weapon" or my recently completed ultra lightweight friction drive project?

If you are cyclist who really wants an ebike that pedals like a roadbike, my last build may be of interest to you.

Hi Kepler,

Thanks for contributing to my newb post. For clarification, I was referring to your old, "Eboost" friction drive project. I believe your website is still up and running http://www.eboo.st/. Specifically, I was referring to the "center/mid-mount" version. Although now that I re-read my post, I can see that "mid-drive" was probably a poor word choice.

I've also followed your more recent full-carbon, TT bike build. You're right in that your latest build is essentially exactly what I'd like to replicate. Unfortunately, I'm limited on access to machining equipment to replicate the bottom bracket mount assembly :/ ... Not to mention, I'm a bit rusty on my machining from my university days.

As a side note, I am part of a local tool share (i.e. hacker space). However, they're only a year old, so it will be at least another year or two before they are prepared for any machining or metal work.

Also, I don't think I'm prepared to throw in for a spot welder to do my own 18560 packs yet. So I'll probably rely on LiPo for the time being.

Thanks for the reference, none-the-less. And of course thanks for your previous builds that have been an awesome source of info!

 

[Neskie]

I'm afraid you have lost me here.
I like elifebike and use their controllers, but never their batteries. Headways, I.M.O., are outdated and the heaviest form factor of Lithium. Why would you want 13 Lb. boat anchor that only supplies 240 Wh's of capacity? That amount of Lipo would weigh about 1 1/2 lb.s.

You're Right! ... I did a bit more reading and it turns out I was just confusing myself ... I misread the battery spec and thought it was ~1kg (comparable to LiPo). It is not. At least I can check that idea of the drawing board

But then again, I'm unsure why you are stuck on 24 Volts. The first step in designing a system is to match the Voltage(system speed) to the desired road speed while keeping the motor speed/whl. size in it's efficient range. Even using a high speed mini, like the Q100 328 in a 700 cc wheel(a poor combo for efficiency), the top speed would only be 16 mph.

A mid-speed mini, like the Q100 (260) for example, in a 700cc whl., run @ 36V, would have a useful top speed of 21 mph.
I used the run this motor @ 9S in order to match the 31 V LVC of my ELB controller and found it to be a nice low-powered system with a top speed of 19 to 20 mph. That's about the lowest Voltage that I feel is practical.

Right Again!

Thanks for the info. I think I would go with a pre-made (commercial) 36V Li-Ion pack to pair with the Q100 (260rpm) on a 700c front wheel. However, I'm leaning pretty heavily towards the friction drive at this point. In which case, I'm back to the Turnigy 6S Multistar packs.

I've been doing the new, 40mi round trip commute for a couple weeks now and have been surprised at how pleasant it has been (unassisted). So I'm thinking the friction drive will be plenty to take the edge off on days where I'm a bit fatigued or there's a nasty headwind. Plus, I'm envisioning taking the kit on and off quite frequently.

 

[Neskie]

So I've more or less put together my shopping list for the prospective Friction drive build:

Main Components:

*Mechanical Assembly by Machine Works (based in UK)
http://www.instructables.com/id/Friction-drive-build-for-bikes/

Motor - Turnigy Aerodrive SK3 148kV - $80 USD
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=71864

**Controller - KU63 from BMS - $15 USD
https://bmsbattery.com/ebike-kit/751-s-ku63-250w15a-6mosfets-controller-ebike-kit.html

Batteries - Turnigy Multistar 6S 5200mah Lipo Packs (x2P) - ~$80 USD (with shipping)
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=56841

Charger - Turnigy Reaktor 250W 10A Balance Charger - $50 USD
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=78379

DC Power Supply - 12VDC 900W (ebay) - $35
http://www.ebay.com/itm/171938269577

* Note: I was very happy to find this machinist in the UK willing to put together a mid-frame-mounted, friction drive assembly. You may notice it mirrors the design of Adrian's Commuter Booster.

**Note: I plan on modifying the UVLimit on the KU63 to better match the 22.2V/6S Lipo pack that I'm using. I'm also hoping to put together a setup that relies on a single, push button switch instead of a throttle (again, like Adrian's Commuter Booster)

Odds and Ends:

Triangle Frame Pack for Batteries - TBD
PAS Sensor from BMS
Parallel Harness (Y-connector) for LiPo main leads - for both parallel charging and discharging
Parallel Harness (Y-connector) for LiPo balancing leads - for parallel charging
Assorted connectors- TBD

Possible Add-On's:

Speedict Mercury - Android/Bluetooth Governer for controller
- I would be using this to limit the output of my controller to limit speed or extend range. I am also hoping I can setup a minimum speed before the drive engages

Cycle Analyst
- Probably a better controller for performing the same duties as the Speedict, but I'm not fond of the extra wiring and display at the handlebars


So that's what I have so far. Please feel free to throw in your 2 cents (hopefully before I go throw through with all the purchases

 

[TheBeastie]

Speedict Mercury - Android/Bluetooth Governer for controller
- I would be using this to limit the output of my controller to limit speed or extend range. I am also hoping I can setup a minimum speed before the drive engages

If I were you I would just go for a Hub cassette motor with a sinewave PAS controller setup.
I ride PAS only and the S-series controllers and LCD are basically designed for PAS ebikers..
Cassette compatible motor with 32 holes so you can lace it into a standard road bike wheel. If you don't want to lace your own wheel its still cheaper to get some one locally to do it for you, the rims at BMSB are crap and they as far as I am concerned deliberately don't lace wheels properly but everything else I get from them is fine.
https://bmsbattery.com/ebike-kit/651-q100c-cst-36v350w-32-hole-rear-driving-hub-motor-ebike-kit.html
250w sinewave SLCD compatible controller
https://bmsbattery.com/ebike-kit/546-s06s-250w-torque-simulation-sine-wave-controller-ebike-kit.html
This LCD displayer (select black one) allows you to have 5 different levels of motor assistance from 0 (zero motor help) to 5..
Also has LCD symbols that tell you if ur brakes are engaged etc which comes in really handy because I can't tell you how annoying it is to find out your ebikes just not going simply because the controller has wrongly received the brake signal when it shouldn't have.. this single feature has saved me days of time.
https://bmsbattery.com/ebike-kit/670-s-lcd3-lcd-meter-for-s-series-controlers-ebike-kit.html
Speed sensor (but I dont think u need this as speed sensor inside the q100c motor!)
https://bmsbattery.com/ebike-kit/550-speed-sensor-ebike-kit.html
PAS sensors.. get a few different types of these as having to reorder one blows the budget due to shipping..
https://bmsbattery.com/ebike-kit/579-ten-poles-pas-pulse-padel-assistant-sensor-ebike-kit.html
I have yet to put the PAS sensor below on, I believe I need to change the settings inside the LCD to make it work, going to try it one day..
https://bmsbattery.com/ebike-kit/705-dual-hall-sensor-12-signals-easy-assembling-pas-ebike-kit.html

Thats about everything.. with this type of LCD setup you can choose/build a wider variety of batteries, as they adapt to different voltage setups, those old KU controllers have nasty hard cut off voltages that are very difficult to mod and match with the right battery.
I have had enough KU controllers and Sinewave controllers to safely say that KU controllers are old out dated as shit and people who still buy them are idiots.
For battery pack holding I like frame bags either from EM3EV or Lunacycle... I had both frame bags.. the Lunacycles look better (zip tie version) but the EM3EV have considerably stronger zipper setup.

 

[motomech]

I agree with Mr. Beastie 100%.
Aside with the fact I don't think the KU63/65 is compatible w/ the Friction drive motor listed, it is a harsh controller.

The rider who doesn't mind to take the time to set up a SO6S based controller w/ the LCD-3 display, is rewarded w/ a great PAS experience @ a budget price.

The 5-level, CURRENT limited "torque imitation" system offers amazing "feel" and versitity .

And when coupled w/ the Q100C, the motor is so quiet that it is almost spooky.

And the new Li-Ion batteries w/ intergrated controllers are just "icing on the cake".

The thing about hub motors @ low power is they are so reliable, just install and forget.

 

[Kepler]

The KU63 /KU65 will work with RC style Outrunner motors. I use them all the time. Reason I use them over and S06 is that I can modify them more easily. With a RC Outrunner motor, you need to select the battery voltage very carefully as you can easily exceed the max electrical voltage of the controller. I use 200kV motors and have found I can use up to 7S (29.4V hot off the charger). A 150kW motor would handle 8S voltage (33.6V hot off the charger). However you will need to modify the low voltage cut off and as such need to be confident solder new resistors on to the circuit board to do so. There is good documentation on how to do this. Also I don't use the PAS function on a friction drive anyway.

That being said, I totally agree, the S06 a better low cost fit for a small hub setup and would use that any day over the KU63/65.