My experience converting an e-Bike

I purchased a decent inexpensive "Nashbar Flat Bar Road Bike" ~$230 from Bike Nashbar back in April 2017 and rode it twice over the next 2 or 3 years. Life got in the way, I became even more sedentary.  With just a few months to go before I retire, I decided it was time to get back on the bike and spend my days being active walking and biking.

Thinking that an eBike could help me up the hills, I figured I could probably get some more seat time for more exercise.  I found this reasonably priced kit on Walmart.com to convert my regular hybrid bike to an ebike for as little money as possible. 

A new project with new stuff to learn will be a good time.

 

After looking at tons of options on Amazon and Walmart and trying to figure out if I should purchase a 48v or 36v motor, I decided to go small for my first project because lower voltage would mean fewer batteries, lighter weight and lower overall cost.

I didn't want a front wheel drive bike though it might be slightly easier to install. I think it's probably the better option for less mechanically inclined people but I suspect the thought of installing all those parts would scare off 99% of most potential buyers.  I chose this kit because it included new correctly sized spokes for hanging the motor inside the rear wheel on my bike but I was not aware that the motor needed 36 spokes and my bike only had 32 spokes until I took my rear wheel apart and tried to weave the spokes into the motor.

There was no way to evenly install the spokes from a 36 hole hub to 32 holes on the wheel so a new wheel (~$37) was ordered. I decided to go slightly wider (17mm for old, 19mm for new) on the wheel but needed to be mindful of still fitting under the narrow frame of my hybrid bike.  The tire width is increasing from 28mm to 35mm. I was thinking a wider tire and wheel would be better for the increased weight though it's nonsense, because I'm easily 25lbs heavier than the last time I rode the bike. I'll keep the original front tire for now but might swap the front after a few rides.

The rear gear cassette did not fit the new motor hub due to the way it mounts, so I had to find a 7 cog freewheel instead.  I purchased a cheaper option but it did not have the same gearing so I'll loose some hill climbing ability on the low gear but gain some top speed on the high gear.  Probably not a huge deal with the motor assist.  I discovered a slight mismatch of the mating surfaces that caused the wheel to lock up once the cassette was tightened down when the cog rubbed on the motor hub shoulder and realized that I needed a spacer to allow the cassette to spin once it was mounted so I 3d printed a 1.5mm tall washer to sit on the motor hub before installing the new cassette. This one small issue could have gone unnoticed and caused trouble down the road if I wasn't double checking the wheel spinning.

When I tried to install the pedal assist sensor, I was not able get the crank off using conventional tools so I had to buy a crank puller to get it off. Some hot glue to keep the sensor in place.  I'll probably need a few dabs of epoxy because the hot glue will probably not be as secure as I need it to be.

While I wait for the batteries to arrive, I will install the rest of the parts and zip tie the wires to make it as neat as I can.  I will need to figure out how to mount the battery, and how to wire everything together with the battery pack, battery management system and charger.

Spent several days designing a battery box and mounting solution for my battery pack. I hope I don't have to reprint any of these parts because these will take a long time to print. First estimate is about 1 day for the mount and 2.5 days for the box.

Designed a mount for the display as well as a guide for the wiring to tidy things up a little. I did not like the bar clamp that put the display off to the side of the handlebar.

Old LED Display with 3d printed guide below
and display mount above the bar

I completed the bike but am not happy with the size of the battery box with respect to the bike.  It's just a big ugly box that makes me want to find a way to hide it better.

I was concerned with the bike having enough power to take me up the hills and it does struggle on throttle only, but the original intention was for the motor to help me up the hills and I think it certainly does that. 

The pedal assist makes biking almost too easy, so I'll probably keep the assist level low until I need to get up a hill (or just not use any assist at all). Not needing to shift very often makes for a very different riding experience.

I feel like I need just a little more power for getting up the hills and I already have a different controller (22amp max vs 15amp max) with an upgraded display. Once I hook it up, I can determine what to do with the battery box .

Overdriving the hub motor will require cooling so I will research using 2.5 ounces of synthetic transmission fluid injected into the disc brake rotor mounting hole on the hub motor body.

I found the motor specifications for a similar hub motor to mine on AliBaba which is a business to business site that connects suppliers with wholesalers or manufacturers. They tend to list more specifications than ordinary websites and I used these motor specifications to set the P1 setting on my controller. The reduction ratio and magnets should get me close to my hub motor's specification since they are pretty much generic products by now.

P1 = 101

P2 = 1 (6 showed speed reading too low)

P3 = 1 (power based assist instead of speed based assist)

P4 = 1 (must pedal to start)

P5 = 17 (smart voltage for 52v, 0-use actual voltage for power monitoring or 4 for 36v battery)

C1 = 01 (8 magnet PAS)

C2 = 0 (sinewave?)

C3 = 8 (PAS assist level is restored from last setting)

C4 = 0 (p4=1 & c4=1 : walking assist from stop and full throttle after pedaling, p4=0,c4=0 for full throttle whenever)

C5 = 08 (limit max current to 19 amps)

C7=1 cruise control

C8=1 show motor temp

C12=7 (translates to 45V for a 52V battery, 41.5v min voltage for 48v , 31.5v min for 36v battery) 

Upgrading to this controller allows the 250w hub motor to run as much as 720w and I'm expecting to be able to notice the improved capability on the hills but the sine wave type controller seems to run a bit quieter.  I'll need to remember not to max out the motor for long periods of time because the increased current will make it run hot.  I have the max speed set to around 20mph which should be a conservative limit.

Overall, it has been a great project and I already have plans to electrify my wife's bike and have purchased a used bike for $15 and plan on electrifying it for my son.  I have yet to take it very far because I'm physically not in shape enough to range very far from my neighborhood although I have put roughly 17 miles on it over the last few weeks. I need to figure out how to reset my odometer so I can get an idea of actual range in the way I'm currently riding.  I'm taking short trips around my neighborhood to work up my stamina as well as shake out any ergonomic issues before I go out on a longer ride.