Need advice for my commuter e-bike build

[idealistix]

I am going to build my first commuter e-bike. I have already spent a ton of time on ES, but would like some feedback on my plans. My one way commute is 9 miles, but a longer 10 mile route is probably safer.

I am an engineer, so I cannot help but go about this build in a methodical manner. Decisions step A (see below) will get me to finalize the specifications for the e-bike. Step B will be details on how to actually build it.

Here are my requirements:

Budget: $1,500 for conversion (can go up to $1,800 if needed)
Cruising speed: 25 mph
Max speed: 30+ mph
Terrain: mostly flat, some rolling hills
Range at 25 mph: 20 miles (12 mile range may be ok if I am able to charge the batteries at work)
Rider + cargo weight: 150 lbs
Stealth factor: high (I will need to ride on some sidewalks which is legal in my city, but I'd rather not attract unwanted attention)
Wheel size: 700c / 26"
Brake type: rim if using current bike
Current bike: Trek Verve 1 (http://www.trekbikes.com/us/en/bikes/city/recreation/verve/verve_1/)
Battery chemistry: must be very safe
Upgrade options: I want an "open" system so I can upgrade components easily in the future

Decisions step A:

1. Use my existing bike (Trek Verve 1) or get a different one off craigslist?
2. Rear hub or mid-drive? (I have ruled out front hub)
3. Direct drive or geared?
4. Motor output?
5. System voltage?
6. Battery type?
7. Battery capacity?

Decisions step B (only after I have completed step A above):

1. Brand of motor / conversion kit?
2. Brand of battery?
3. How to mount the battery?
4. Full list of parts to complete build?
5. Vendor(s) to buy from?

My initial thoughts for step A:

1. Use existing bike (Trek Verve 1) - it fits me great, is light weight, and is in good condition. However it does not have disc brakes or shock absorbers. I will ride mostly on smooth roads or sidewalk, so shock absorbers are probably not important.
2. Rear hub - Stealthier, more reliable than mid-drive
3. Direct drive - Quieter, more reliable, tends to be more powerful. I can leave electric assist on (at the lowest setting) to overcome motor resistance even when I am primarily pedaling . I am also fine with slower acceleration and don't have steep hills.
4. Motor output - 1,000W minimum, 1,500W preferred
5. System voltage - 48V, 30A continuous
6. Battery type - LiFePO4
7. Battery capacity - 15AH (maybe 10AH if significantly cheaper / lighter)

I welcome your feedback / recommendations to help my build go smoothly!

 

[Syonyk]

1. Use existing bike (Trek Verve 1) - it fits me great, is light weight, and is in good condition. However it does not have disc brakes or shock absorbers. I will ride mostly on smooth roads or sidewalk, so shock absorbers are probably not important.
2. Rear hub - Stealthier, more reliable than mid-drive
3. Direct drive - Quieter, more reliable, tends to be more powerful. I can leave electric assist on (at the lowest setting) to overcome motor resistance even when I am primarily pedaling . I am also fine with slower acceleration and don't have steep hills.
4. Motor output - 1,000W minimum, 1,500W preferred
5. System voltage - 48V, 30A continuous
6. Battery type - LiFePO4
7. Battery capacity - 15AH (maybe 10AH if significantly cheaper / lighter)

I welcome your feedback / recommendations to help my build go smoothly!

This seems entirely sane, though I will point out that a direct drive rear motor is in no way "stealthy" - they're huge. A geared hub motor that tucks in behind your gears and looks like a big hub is a lot stealthier. They do have a distinct gear whine. In either case, look at rear bags to hide the motor if that matters.

LiFePO4 is definitely sane, and you should be able to do a round trip on 10AH/48v, though it'll be pushing the range of the battery if you do it heavily on the throttle. 15AH is probably a better option if you want to round trip without charging at work. If you can charge at work, just go with the 10AH pack and charge at work.

Are you planning to design a pedal assist system or a pure throttle driven system?

Don't forget fenders, if your bike doesn't have them. Tightly fitted fenders are great for year round commuting.

 

[idealistix]

I had not given much thought to pedal assist v/s throttle mode. I am leaning toward a pedal assist system, but I don't know enough to be sure of it. It'll be great if somebody could provide pros and cons of the two systems.

I will likely be using panniers of some kind, so the rear hub will be somewhat hidden. Maybe something like this: http://www.amazon.com/Topeak-MTX-Trunk-Side-Panniers/dp/B000FIAU0W.

 

[motomech]

My initial thoughts for step A:

1. Use existing bike (Trek Verve 1) - it fits me great, is light weight, and is in good condition. However it does not have disc brakes or shock absorbers. I will ride mostly on smooth roads or sidewalk, so shock absorbers are probably not important.
2. Rear hub - Stealthier, more reliable than mid-drive
3. Direct drive - Quieter, more reliable, tends to be more powerful. I can leave electric assist on (at the lowest setting) to overcome motor resistance even when I am primarily pedaling . I am also fine with slower acceleration and don't have steep hills.
4. Motor output - 1,000W minimum, 1,500W preferred
5. System voltage - 48V, 30A continuous
6. Battery type - LiFePO4
7. Battery capacity - 15AH (maybe 10AH if significantly cheaper / lighter)

1. Mostly smooth might not be smooth enough for that bike, especially approaching 30 mph. Many consider a quality mountain bikes, with their great suspensioin and brakes to be a better choice for those speeds. Personaly, I wouldn't ride anything else.
2. Agreed
3. Nothing stealthly about a motor bigger around than a Frisbee. Geared motors these days are reliable, but if your route has few stops, a DD motor has it's attractions.
4. V X A = W
5. 48V is a good all around Voltage
6. LiFePO4 is heavy and old skool. Li-on is the best Chem. I.M.O.
7. You can buy an extra charger and charge at work. 10 Ah. would be enough.

There is a big difference between an Ebike that will avg. 24 to 25 mph and one that will avg. 28 to 30 mph.
For the lower speed range, you can use a budget motor like the Bafang BPM CST(which allows retention of a Cassette) and possibly one of their batteries.
https://bmsbattery.com/
For the higher speed range, you might want to look at a high speed wind Mac motors from Paul @;
http://em3ev.com/store/
He could supply you with the higher dis-charge battery you will probably need. You will also need a free wheel instead of a cassette.
Higher speeds will also requite a of 52T chain ring or larger, while the easier installed(less expensive) 50T will work at 25 mph.

Bottom line; You can add up the costs for the two different aproachs, but I think you will find a 25 mph avg. will keep you under your budget, while 30 mph might put you over. Especially if you upgrade the donor bike.

 

[wesnewell]

Any of the many 48V 1000W kits on ebay.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=48v+1000w+rear&rt=nc&LH_PrefLoc=1
I won't use bikes with aluminum dropouts. That usually means a cheap bike is a better choice to motorize.
I use 20C rc lipo and have no safety concerns after over 4 years of use. If you want something safer, be aware of the C rates and make sure the pack is capable of at least 30A output.
I's stay off the sidewalks. They aren't safe for you or peds with you on it. And you will be liable for any accident on them or coming off them.

 

[Syonyk]

I had not given much thought to pedal assist v/s throttle mode. I am leaning toward a pedal assist system, but I don't know enough to be sure of it. It'll be great if somebody could provide pros and cons of the two systems.

Bing it.

Throttle: Totally independent drive system in which you have a twist or thumb throttle that applies the motor. Lets you be lazy. Generally uses more power (watt-hours per mile).
Pedal assist: Adds power proportional to your pedal (rate, torque). The cheap systems go based on your pedaling rate. The nice systems (which either means BionX or a factory ebike) detect your torque and boost that proportionally.

6. LiFePO4 is heavy and old skool. Li-on is the best Chem. I.M.O.

Which chemistry are you referring to, specifically?

LiFePO4 is a great chemistry. It's safe (isn't prone to catching on fire, even when abused), it has a very flat voltage across the discharge curve, it has a long cycle life (thousands of cycles), and a long calendar life. You carry an extra pound or two for a pack compared to a more energy dense chemistry, but on a bike rolling down the road at 200+ lbs with a rider, it's a very minimal difference for the advantages it offers.

7. You can buy an extra charger and charge at work. 10 Ah. would be enough.

It depends on the workplace. Outlets are rare in some parking areas, and bringing your pack into your desk every day is rather annoying.

 

[dogman dan]

NMC is plenty safe enough. Just avoid the low quality RC lico battery for better safety. But do what you can to avoid what makes all batteries dangerous, having a cut wire short the thing, or squashing it in a crash which again, causes a short somewhere inside the pack. For your 20 miles at 25 mph, 48v 15 ah of it. Ideally carry it in a triangle bag or box in the frame center. 10 ah fine, if you only need 10 mile range though. If charging at work is actually convenient.

Throttle. Unless you up the budget enough to use the PAS that includes real torque sensors.

Rear hub, if you go hub. 48v, powerful geared one ideal. 25-27mph plenty of speed. Don't put a pig heavy DD on that bike. Different story if you used a heavy bike to start with.

Nothing wrong with the mid drive idea, but a geared hub motor will allow easy riding with no shifting of the bike at all. Just leave it in high gear. Much nicer IMO, for city commute riding. So I still vote for the rear geared motor.

 

[windtrader]

If stealth is needed, then you may as well go pedal throttle, as 25mph with no pedals spinning is a sure bust.

 

[idealistix]

Thanks to all who replied. I have done my research, but it's great to hear from people who have first hand experience.

1. Mostly smooth might not be smooth enough for that bike, especially approaching 30 mph. Many consider a quality mountain bikes, with their great suspensioin and brakes to be a better choice for those speeds. Personaly, I wouldn't ride anything else.

I am strongly considering getting a 26" wheel with the hub motor even though my bike will continue to have 700c on the front. The geometry will change a little but the height difference won't be much (about half an inch) if I have a wider 26" tire on the rear. This will give me a cushier ride and allow me to move on to a mountain bike more easily if the Trek proves to be uncomfortable.

For the higher speed range, you might want to look at a high speed wind Mac motors from Paul @;
http://em3ev.com/store/
He could supply you with the higher dis-charge battery you will probably need. You will also need a free wheel instead of a cassette.

Higher speeds will also requite a of 52T chain ring or larger, while the easier installed(less expensive) 50T will work at 25 mph.

em3ev is on my shortlist of sellers if I decide to get an NMC battery. I am leaning slightly toward LiFePo4 but the higher C rate is tempting.

I had not thought of upgrading the chain ring - thanks for bringing that up.

 

[idealistix]

Throttle: Totally independent drive system in which you have a twist or thumb throttle that applies the motor. Lets you be lazy. Generally uses more power (watt-hours per mile).
Pedal assist: Adds power proportional to your pedal (rate, torque). The cheap systems go based on your pedaling rate. The nice systems (which either means BionX or a factory ebike) detect your torque and boost that proportionally.

After looking into these options, I have decided against cadence sensors for PAS. I will likely go with throttle system unless I get a great deal on a torque sensor system.

LiFePO4 is a great chemistry. It's safe (isn't prone to catching on fire, even when abused), it has a very flat voltage across the discharge curve, it has a long cycle life (thousands of cycles), and a long calendar life. You carry an extra pound or two for a pack compared to a more energy dense chemistry, but on a bike rolling down the road at 200+ lbs with a rider, it's a very minimal difference for the advantages it offers.

Outlets are rare in some parking areas, and bringing your pack into your desk every day is rather annoying.

If I get a 15AH LiFePO4 battery, will I be able to continuously draw 25 amps and get to 30 amps for short bursts?

I may need to bring the battery in to my desk anyway as an anti-theft measure.

 

[idealistix]

NMC is plenty safe enough. Just avoid the low quality RC lico battery for better safety. But do what you can to avoid what makes all batteries dangerous, having a cut wire short the thing, or squashing it in a crash which again, causes a short somewhere inside the pack. For your 20 miles at 25 mph, 48v 15 ah of it. Ideally carry it in a triangle bag or box in the frame center. 10 ah fine, if you only need 10 mile range though. If charging at work is actually convenient.

Thanks for confirming that 48V, 15AH is the sweet spot for my requirements. Triangle bags seem great and are my first choice of mounting mechanism. I will need to compare it to a "hard" mount in the frame center in terms of protecting the battery in case of a crash and ease of removal.

Throttle. Unless you up the budget enough to use the PAS that includes real torque sensors.

Agreed. I like the idea of torque sensors but I may wait on that upgrade.

Rear hub, if you go hub. 48v, powerful geared one ideal. 25-27mph plenty of speed. Don't put a pig heavy DD on that bike. Different story if you used a heavy bike to start with. Nothing wrong with the mid drive idea, but a geared hub motor will allow easy riding with no shifting of the bike at all. Just leave it in high gear. Much nicer IMO, for city commute riding. So I still vote for the rear geared motor.

Hmm .. I have been pretty set on DD motors primarily because of reliability. Would you say that geared hub motors (the good ones) are equally reliable?

 

[Syonyk]

If you don't get stupid with a geared motor, they're quite reliable. Stay within the rated power limits, preferably well within, and you'll be fine.

And, yes, you should be able to get that current of a 15AH pack. I've got a 13AH LiFePO4 pack that sources up to 40A.

 

[alpharalpha]

Did you make a choice yet? I was going to switch out my trek hybrid's suspension fork for the high tensile steel verve one but that rounded thing near the top makes it so you can't put anything larger than a 35 tire and if you go front hub you'll need at least a 37. I wouldn't doubt it if the verve has the same welded kickstand in back that also prevents anything larger than a 35. Currently I have a 37 on the front and 35 in back. One of these days I'll cut off that kickstand and put a 37 back there too. I suppose you could cut off that rounded thing on your front fork and then it would fit a larger tire, I just didn't want to spend $80 for something I'd have to mod. Post some pics as you go along, if you diy it all yourself it's an interesting project. I just wired some cree lights to the pack; I keep the pack in a jandd rack pack 2, if you're looking for stealth. I also have a front rack that helps distract from the big disc but a rear rim with panniers would be more stealthy. 30 mph is pretty fast on a bicycle, things come up on you real fast, I'd start out with 20 mph. 30 mph won't feel fast while you're riding but if you ever crash at that speed it'll be a real lesson in kinetic energy. I prefer 15 to 20 mph, at least it gives me more reaction time. Have fun and be safe.

 

[idealistix]

I moved recently and had not taken my bike out on my commute route until today. I realized pretty soon that I will need a bike with at least a front suspension. I have a two mile stretch where the ride on my Trek hybrid is very bumpy. I have to start looking at Craigslist for an MTB now. :x

Before I deal with the craigslist crazies, should I consider a cheap Walmart bike like Genesis V2100 or Mongoose Ledge?

 

[wesnewell]

The Genisis V2100 has aluminum dropouts. Look for a bike with a steel swing arm and dropouts like a Mongoose ledge. I've got ~10K miles on mine although I did have to replace the bottom bracket bearing after a year.

 

[dogman dan]

One nice thing about the NMC, is 48v 15 ah is pretty small, able to fit in triangles a bit better. But, now you are looking at suspension bikes, your triangle will be a lot smaller, or even so small it's good only for a controller.

This can make not choosing heavier lifepo4 even more important, if you are stuck carrying the battery on a rear rack, it just can't be much over 10-12 pounds. By 15 or more pounds for lifepo4, it affects the handling of the bike a lot.

Re the bike, I'm a bit amazed Wes can stand his bike after that many miles. All steel bike frames can last very nice. But I found other models of cheapo FS mtb's I tried had very floppy alloy frames (but steel swing arms). I just couldn't stand all the tail wagging. Worth noting, he has his battery up front, so not having the rack weight will help a lot. I got bad tail wag with a battery, and two panniers full of groceries on the rear of the bike. Today, I have suitable long tail cargo bikes for that kind of use.

Myself, I NEVER regretted spending a bit more for a used, but reasonably good Giant MTB for my commute. It's frame is heavier than most, nice thick strong alloy in that thing. I guess back in it's day, it was a DH bike for that year. Not beer can thin like the bike shaped objects at walmart. And you want a good fork, so at the very least make sure the BSO you pick has a 1 1/8 headset so you can do a fork up grade.

Anyway, a good frame is worth the cost IMO. Alloy dropouts in back are fine, provided they are good for use with torque arms. Like this. Some flat space around the axle of the wheel makes using a simple and effective torque arm easy. Steel is nice, but you only find that on crappy full suspension bikes.

If you want steel, build a longtail. Longtails handle the bumps great, because your ass is not hanging over the rear wheel.

 

[idealistix]

Thank you all for the very helpful advice. This is what I have decided as the answers to step A:

1. Short answer: convert my current bike first. It may not be the most comfortable option, but it will be safe for a starter build.

Long answer: I know that my long term bike will be a MTB with a front suspension and maybe rear or seat post suspension as well. I will get a good quality used bike but I don't have the time to research and shop for bikes now. I also don't have a good understanding of my requirements for a new (to me) bike. I have absolutely no experience with how electric bikes feel while riding. I will try it out on my current bike and figure out what improvements are needed for my long term bike. I will also get a 26" wheel since that is the most common MTB size. The geometry will be close enough with the 700c wheels in the front on my Trek.

2. Rear hub

3. Geared - I am more confident now that they will be reliable

4. Motor output 1000W

5. 48V system

6. NMC battery - good combination of light weight, safety, and output

7. Battery capacity - minimum 13 AH, up to 17 AH

On to step B now ..

1. Brand of motor / conversion kit - my first choice is this upgrade MAC kit from em3ev: http://em3ev.com/store/index.php?route=product/product&path=45&product_id=186

Options:

Battery - see below
Max speed - 30 mph
40A controller
26" Alex DMC24 CNC
Thumb throttle AND half twist throttle: I will see which one I like and keep the other as a spare
HWBS sensor
Disc spacer: will get it just in case my next bike has rear disc brakes
Rear torque arm
7 speed freewheel
CA-3 display

2. Brand /size of battery -

13.3 AH 20R battery from em3ev: http://em3ev.com/store/index.php?route=product/product&path=35&product_id=132.
Second choice is 15.2 AH 20R battery: http://em3ev.com/store/index.php?route=product/product&path=35&product_id=134

I wonder if 2AH more is worth $65.

3. How to mount the battery - rear rack.

4. Full list of parts to complete build?

Am I missing anything?

5. Vendor(s) to buy from? Listed in order;

em3ev
ebikekit
ebikes.ca

 

[wesnewell]

Get the DX32 rim instead of the narrow DM24 if you plan on using 2.0" or larger tires.

 

[idealistix]

I found a good deal on a Trek 820 on craigslist - a couple years old but never used for $225. The bike was literally like new - the seller got it as a gift but never even took it off the wall mount. I have taken a couple of test rides and the 820 with the front suspension and wider tires rides a lot smoother than the Verve.

I will need to take the battery off the bike everyday at work. I'd appreciate ideas on the best way to mount the battery in order to make battery removal and re-installation an easy process. I really like the idea of a frame triangle bag for the weight distribution but it seems that a Topeak MTX bag on a rear cargo rack will be easier to remove.

This is the full list of components that I am planning to order from em3ev. Should I add anything to the list?

Upgrade Mac Kit with 50V High Power Battery (up to 50kmh/30mph)
- Battery Type: 50V 15.2Ah 14S8P20R Rectangle, 5A Chg OR 50V 17.5Ah 20R Triangle, 5A Chg (for $125 more)
- Max Speed: ~50km/h (30mph) - 8T motor
- Controller Type: 40A 12 Fet (36-52V, IRFB3077)
- Front/Rear Motor: Rear
- Wheel Type: 26" Alex DX32 CNC
- Spoke Type: Sapim Upgrade (Black)
- Throttle Type: Half Twist
- Ebrakes: HWBS Sensor (1pc)
- Disc Spacer: Without Spacer
- Torque Arm: Rear Rev4 (1pc)
- Freewheel: 7sp DNP (11T)
- Display: V3 CA-DPS

DNP Extractor Tool
Ebike Tester
Sapim spokes (Black): 4 count cut to same length as used in the DX32 wheel

 

[Raged]

The smaller battery will be ok.

Get a thumb throttle as well. I find the grip throttle dangerous when you hit speed humps, so you might find thumb throttle easier ( get 2 in case you stack and break it).

You dont need the ebike tester. Paul's kit is plug and play and tuned good right off the bat.

 

[idealistix]

Raged: thanks for the feedback. Coincidentally, I was reading your build log yesterday. I hope you heal up quickly!

I logged on to mapmyride.com and created this elevation profile of my commute. It's 10.25 miles one way .. I'm guessing that the 8T motor on 26" wheels will handle this just fine. I also think that most of the ride will be at 20 mph or less and I will go up to the top speed only for about 3 miles.

 

[Raged]

Raged: thanks for the feedback. Coincidentally, I was reading your build log yesterday. I hope you heal up quickly!

I logged on to mapmyride.com and created this elevation profile of my commute. It's 10.25 miles one way .. I'm guessing that the 8T motor on 26" wheels will handle this just fine. I also think that most of the ride will be at 20 mph or less and I will go up to the top speed only for about 3 miles.

Thats a pretty nice ride with rolling hills =)

Before you order anything, check that the battery fits inside the frame. I started off with a rear rack as it was the easiest but it had a tendency to try and flip the bike (too much power and bad weight distribution). When I was doored last year, the mounts holding the box to the rear rack sheared and I was lucky I had additional straps to hold it down. Battery on rear rack was a missile to the back scenario.

So yeah... I highly recommend putting the battery near the middle.

The other design I was looking at was ultra stealth top tube front panniers like this :

http://www.ebay.com.au/itm/MTB-Frame-Pannier-Bicycle-Cycling-Two-Sides-Front-Tube-Bag-Saddle-Bike-Bag-/251955767756?pt=LH_DefaultDomain_15&var=&hash=item3aa9bbe9cc

Not necessarily that one but the bigger size units are 16(L) x 11(W) x4.5(H). The bigger the better... This just happens to fit 4 x Turnigy 5000mAh lipo batteries for a 2P 10Ah setup. Obviously this comes with the warnings on Lipo yada yada. You'll save on the cost of batteries but you'll need a BMS and a RC hobby charger (worth having one anyway to properly charge other batteries). Also you need rubber padding to protect those batteries from flapping against the frame.

You also don't need a CA V3. Its nice and all, but you don't need it. You can generally judge how far you have left after 2 weeks riding.

But there's options to consider =)