DIY ebike build using an older mountain bike. Bafang BBS02 750w 48v mid-drive.

I had some visitors, we rented e-bikes (rad brand), went about 30 miles, climbed six miles up a really steep climb to start then most of the rest was downhill or levelish, and now I really want one.

Did some research, was thinking hub drive to begin with (where the stock wheel is replaced with a motor driven wheel), but then realized I'd be much happier with a mid drive (which is mounted in the middle of the bike and utilizes the existing gears/chain).
I like simple, I don't like relying on moving parts, so hub drive really makes a lot of sense in that regard.
Logically, mid drive makes more sense since it's able to use gearing.  I don't like that it depends on the chain and sprockets, but the performance over hub drive seems to be worth it.  
I've ridden mountain bikes for thirty years.  Replacing chains, sprockets/cogs, pretty much anything is no big deal.  I've never taken a bike to a shop/mechanic.  It's all pretty simple.

The bafang mid drive motors seem to get good reviews.  I considered a higher wattage motor but decided the 750w would be good enough.  I'm hoping for over 30mph top speed on the level, and hopefully 50 mile range (level ground, little to no pedaling with the battery I'm getting).  The battery is going to be a 52v, 40amp, 20 amp hour rated.     ​

My old mountain bike that I haven't used in a couple of years is the guinea pig it's going to go on.  It's a high quality steel frame (chromoly).  It's a 2001Kona Explosif, with a Fox front fork (that's got too much travel for the frame but it was free), and a mismatch of other parts that work for me.  It currently has mechanical front disc brakes, and rear rim brakes.  I have no doubt rim brakes front and rear would be fine, but if I get around to it I'll pull a mechanical disc brake off of one of my other bikes, swap the wheels, and throw it on this bike.  
The bike had a bent rear derailleur hanger that I just straightened out the best I could, and also a bent Sram X9 rear derailleur that was also bent that I tried to straighten out (the reason I haven't ridden it in a while).  Seems to be shifting fairly well, but I don't know if the torque of adding a motor might be more than it can handle.  I'll try it and see.

I'm also going to order a new 9 speed rear cassette, and a new chain.  From my experience, trying to use a new front chain ring (which comes with the new motor) with older rear cassette and chain causes skipping due to the way the parts wear out.  It's best to have all three in the exact same state of wear, so that'll be all brand new.

I'm going to tear apart and clean the bike and parts I'm using today.
I just ordered the motor and other parts a minute ago.  Motor should be here last, around the middle of November, hopefully sooner.

Here's what I'm going to use.

Motor: https://www.amazon.com/gp/product/B099Z7N56Q/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Battery: https://www.amazon.com/gp/product/B09CD1J91Q/ref=ewc_pr_img_1?smid=AYCFYPLZ6QNUQ&psc=1

Chain: https://www.amazon.com/gp/product/B000RWE868/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Rear cassette: https://www.amazon.com/gp/product/B00LAPEX9I/ref=ppx_yo_dt_b_asin_image_o02_s00?ie=UTF8&psc=1

$1,016 total including tax.  Ouch.  I know there are complete ebikes for less, but I don't think they'll be anywhere near the performance as far as power, speed, and range go.  I might be wrong?  :)

I wish you the best of luck! I had the same idea for my bike. I was watching a few ebike videos on YouTube today and one of the bikes got up to 38mph.

I have been riding my BBS02 conversion for my daily commute for the past 15 months or so. I love it.

A few immediate thoughts based on what you have written above.

1) You want 30mph on the flat. It's not going to happen. The BBS02 has a drive motor rev limit, a bit faster than a human would comfortably peddle. It won't turn the front cog much faster than you can peddle it yourself. On a normal bike you may expect to hit 30mph on the flat BUT the BBS02 replaces the front 3 speed gears. The end result is you lose slightly on the gearing range available. Your top and bottom gearing ratios are not quite as high and low.

When the motor is not running you will find it more difficult to hill climb - eg with a flat battery - because you don't have a really low granny gear to work with. Not a problem when the motor is working.

I get 20mph using pedal assist on the flat, and 25mph on the flat using the throttle.

2) You NEED better brakes than the rim brakes. The bike is heavy, and you will end up going faster than you are used to. My conversion is based on a donor bike with disk brakes, and I am very grateful for them. Most of the time it would not be an issue, but I have to stop at the bottom of a couple of steep hills and I have had my fair share of idiot drivers cut me off.

3) Your battery sounds awesome. Mine is 48V and 12.5Ah. It get about 15 miles of max power/high speed on a daily basis. If i dial the pedal assist down I get much more range. I could probably nurse 40 miles out of it cruising at more like 12 to 15 mph.  How are you planning on mounting the battery. Yours is likely to be twice as heavy as mine, mounted on the water bottle lugs on the frame. I'd be concerned about a heavier batter mounted the same way. Rear pannier frame?

4) You'll get hooked. I use mine year round in all weather. It replaces a car for us as family. You'll probably find you want to be able to eg pop to the shop and carrier bits and pieces. My pannier bags get daily use, and I'm thinking about a rear box as well, so I can get more stuff home.

Best of luck. Looks like you’ve done your research. I went through the same process as you wanting to upgrade my cargo bike. I have a Rad Runner, so know the joy of pedal assist.

For a long time, I was going to install the same mid drive that you’ve selected. My cousin has the same cargo bike as me and he’s going the befang route.

I chose a front hub as my cargo bike is my work horse and not for kicks, which is what you’ll be getting with your conversion. The front hub will just make it easier on the hills which is all I’m after. I have a good set of gears already.

You are right to get new cassette and chain. You might want to think about getting two of each though. Some bike parts are really hard to get hold of with current supply chain issues. A mid hub transfers way more force than the parts were originally designed for, so expect heavy wear and shorter life. Keeping your drive chain clean will help. I’d go as far as to pack a chain tool and spare chain on every ride.

Please keep us up to date with your transformation. Probably worth a few points towards the odd ball badge.

Michael Cox wrote:I have been riding my BBS02 conversion for my daily commute for the past 15 months or so. I love it.

A few immediate thoughts based on what you have written above.

1) You want 30mph on the flat. It's not going to happen. The BBS02 has a drive motor rev limit, a bit faster than a human would comfortably peddle. It won't turn the front cog much faster than you can peddle it yourself. On a normal bike you may expect to hit 30mph on the flat BUT the BBS02 replaces the front 3 speed gears. The end result is you lose slightly on the gearing range available. Your top and bottom gearing ratios are not quite as high and low.

When the motor is not running you will find it more difficult to hill climb - eg with a flat battery - because you don't have a really low granny gear to work with. Not a problem when the motor is working.

I get 20mph using pedal assist on the flat, and 25mph on the flat using the throttle.

2) You NEED better brakes than the rim brakes. The bike is heavy, and you will end up going faster than you are used to. My conversion is based on a donor bike with disk brakes, and I am very grateful for them. Most of the time it would not be an issue, but I have to stop at the bottom of a couple of steep hills and I have had my fair share of idiot drivers cut me off.

3) Your battery sounds awesome. Mine is 48V and 12.5Ah. It get about 15 miles of max power/high speed on a daily basis. If i dial the pedal assist down I get much more range. I could probably nurse 40 miles out of it cruising at more like 12 to 15 mph.  How are you planning on mounting the battery. Yours is likely to be twice as heavy as mine, mounted on the water bottle lugs on the frame. I'd be concerned about a heavier batter mounted the same way. Rear pannier frame?

4) You'll get hooked. I use mine year round in all weather. It replaces a car for us as family. You'll probably find you want to be able to eg pop to the shop and carrier bits and pieces. My pannier bags get daily use, and I'm thinking about a rear box as well, so I can get more stuff home.

Hi Michael, I saw in another thread that you had done the conversion with the same motor.  Thanks for the input.

1.  Other people "claim" about 32-34mph top speed in other videos using the same setup.  I think the 52v battery over revs the motor if what I read is right?  Not sure.  I'll post back on here what my top speed is when I try it out.   Yes, losing the triple in the front will limit both high and low.  I have a 1 X 10 mountain bike with 29" tires that I use, and I run out of human powered rev's when I get over 40mph downhill on the street.

2.  I'll have to respectfully disagree that rim brakes are or will be inadequate.  30 years of mountain biking on cliffs, on singletrack in adverse weather conditions, on high speed downhills (both dirt and paved over 50mph), etc, and I never had a problem locking the rear (or front if I wanted to) using rim brakes.  
I know disc brakes are "sold" as being superior.  That is not my personal experience.  They're different, they have different characteristics, they perform better in extremely wet conditions (I live in the very dry desert), and people are told they are better and to UPGRADE (ie. spend more money).  To me, having used both, it's nonsense.  Bottom line is I can lock the wheels up on either disc or brake.  Only a stickier tire would make a difference.  I weighed 230 lbs in my thirties and they worked great.  I now weigh 170lbs.  The kit + battery will put me at less than 200lbs.  I have no worries about rim brakes both front and rear being more than capable.  All that being said, the front already has disc, and the rear will stay rim (my spare disc rear rim/wheel has a broken spoke, and I know enough to know that once one spoke brakes......it's a short matter of time before another....and then the whole wheel needs new spokes.)

3.  The battery is a triangle shape and mounts using velcro straps onto the frame.  I very well may fabricate a triangular box for it that is lockable, but that would only be if I started using it to run errands where the bike would be unattended.  For now, it's purely for fun.  In the future, I hope it's more utilitarian where it will replace my car for at least some driving around.  I'll have to see how it goes.  I'm really curious to see how far it will go on a charge.  I'll let everyone know once I get it going.  

4.  I hope you're right.  I used to ride a lot more often a few years ago, almost always mountains/dirt.  These last few years I've not had the desire so I'm looking for a motivator of some sort to get me on the bike.
Yes, I'm already thinking of building a trailer to haul stuff on.  I have lots of spare wheels, a welder, spare metal tube, and a lot of free time.  I just am not sure what I'd haul right now.  Maybe my dogs?
I will say this.  I AM ANTI-ELECTRIC BIKE FOR SINGLE TRACK MOUNTAIN BIKE TRAILS.  I have very sternly told people on ebikes to get off bike trails where motors are not allowed.  I do not like that novice riders are going on advanced routes.  I do not like the speed at which ebikes encourage people to skid on turns, or throttle up hills in the dirt.  I foresee trail closures due to ebikes in the future.  This saddens me as a life long mountain biker.  Hopefully I'm wrong.
I WILL NOT ride this bike on trails that are designated not for motorized use, which is most of the trails I like to ride in my area.  It will mainly be for street use, or dirt roads that cars are allowed on.  I have hundreds of miles of desert dirt roads I can explore right outside my door.  

Edward Norton wrote:Best of luck. Looks like you’ve done your research. I went through the same process as you wanting to upgrade my cargo bike. I have a Rad Runner, so know the joy of pedal assist.

For a long time, I was going to install the same mid drive that you’ve selected. My cousin has the same cargo bike as me and he’s going the befang route.

I chose a front hub as my cargo bike is my work horse and not for kicks, which is what you’ll be getting with your conversion. The front hub will just make it easier on the hills which is all I’m after. I have a good set of gears already.

You are right to get new cassette and chain. You might want to think about getting two of each though. Some bike parts are really hard to get hold of with current supply chain issues. A mid hub transfers way more force than the parts were originally designed for, so expect heavy wear and shorter life. Keeping your drive chain clean will help. I’d go as far as to pack a chain tool and spare chain on every ride.

Please keep us up to date with your transformation. Probably worth a few points towards the odd ball badge.

Thanks Edward.  I'm a fan of almost all your movies!

I really wanted to go with a hub motor.  Ugh, I read about the wear and tear on the gears using the mid drive.  I can't imagine the chain falling off into the rear cassette/spokes under load, or some kind of jam happening with the gears using the mid drive.  In all honesty, in my mind, the hub motor makes more sense.  It's "nicer" to the bike and components.   I think I will end up doing a hub drive on another bike.
I LOVE the idea of the front hub drive......but, then I think a bike was never designed to be pulled from the front fork.  When I think about it, it's a big lever pulling on the frame, stressing the front tube way more than it was ever designed for.   A rear hub motor makes more sense to me.  The front hub makes more sense to change out, that's for sure.  I've not read of anyone having any problems using a front hub and frame issues.   I'm not an engineer.  Maybe it's not a big deal.

Good point on the spare parts!  I work at a warehouse and let me tell you, stuff just isn't coming in.  Good advice on getting spares while I can.  It's inevitable that I'll use them (ebike or regular bike) so I just might get some spares.  Nothing will go to waste.  Good idea.

I will absolutely update when I get it going.  I'm really curious to see how it works.

Got the battery today, and I also got some pedals I ordered off of Amazon for another $20.  
The battery is a beast!!!  I had to take a picture of it next to a car battery for reference.  It's about 1/3 the size of a normal 12v car battery.  
It fits inside the bike frame just fine, but it is really heavy for velcro straps, so it'll be interesting to see how that works out as far as bumps and  rough terrain go.  
I'm thinking metal hose clamps with old inner tube rubber to protect the frame will end up being what I use/need in place of the velcro.

I HAD to paint the white front fork black.  It looked awful white on the bike.

The motor supposedly shipped and will be here really early.  Monday it says.  
A lot of reviews say that parts come in three different shipments from fabang, and the seller on Amazon even said to email them if some parts from the kit are missing, so I'm not sure what to expect, or when I'll actually be able to get it all together.

Just found a video of almost my setup.  The battery appears to be exactly the same.  The motor is the same.  The bike has 29" wheels so it'll theoretically go faster than my 26" tires given the same rpm's.  

He claims a top speed of 36mph.

This guy lives in Northern Utah, and converts old bikes into e-bikes for a living.  He's got the gears in my head spinning that it might be a good way to make some extra cash around here.  E-bikes are super common to rent and ride out here.   Old bikes are inexpensive and commonly found used in great shape.

I actually had this crazy idea a long time ago to start a micro greens business, and do home deliveries on my bike (keeping it green).  
Due to two dogs that were somehow genetically engineered to shed hair faster than it's possible to grow it....I've been reluctant to even try to sell them due to dog hair in the product concerns.  I need a separate "lab" away from my living area to keep the greens free from hair.  Yes, there's that much, lol.

Here's the video.

Impatiently awaiting the motor and chain.......

Got the new rear cassette installed.
Painted the front rim black.  It was white.
Swapped out the Sram X9 rear derailleur with a Shimano XT rear derailleur.  The Sram was sloppy feeling so I ditched it for the good Shimano.  
Got the Shimano XTR rear freewheel/hub installed.
Mounted the new stem and the much wider handlebars.
Tie wrapped Frankenstein to the wider bars.

Took pictures.

Made a bracket out of some scrap metal laying around.

Nice! Good to see the project coming together.

re top speed - the over voltage on the battery (56v instead of 48V) and the larger wheels will likely account for the observed difference in top speed. Especially if your 9 speed gear also has extra range over my 7 speed.

A few things to look out for: It is apparently quite possible to overheat these motors if running at high power, especially if at the higher voltage. The advice is to change down a few gears and make sure that the motor is running at max RPM. I don't understand all the details, but it apparently puts a lot less strain on the internal gearing, and leads to less heat build up. I didn't account for this initially and spent a lot of time in overly high gears, letting the motor bog down a little. At the end of some of my commutes the motor was HOT to touch. Since changing riding style a little it gets less hot. I've much more careful now to stay in a middling gear if there is even a slight incline. Its the difference between 21mph and 23mph, but the motor seems much happier.

Have you looked into programming the controller? Mine came out of the box with just three assist levels. I bought the cable to connect to my laptop and adjusted it to use 9 levels. There are video guides on how to do this. It really helped.

Hi Michael,

Yes, the gearing and the wheel size should make a difference.  I got the 46t front ring, and the rear small ring is an 11, my tires will be 26" and I'll be running high pressure in semi-slick 1.9" treads.  

I've watched a bunch of builds from many people.  The guy who's video I linked in the other post claims that Bafang doesn't seem to have a standard when it comes to programming the output the controllers do.  One controller might throw out more power to the motor than another, based on his observations.  He builds e-bikes for a living and claims to have done hundreds of conversions.

Yes, I've thought about programming, I actually almost bought the cable for it on Amazon yesterday but decided to hold off.  
Oh that reminds me, yesterday I did buy the shift sensor cable that cuts the motor off during shifts.  Do you have that on your setup?

I've heard about the motors heating up with the higher voltage (which is a concern here in the summer because my daily high for three months of the year is 105F on average).  I've also heard people claim there are more failures with the motor when running the 52v batteries.  That makes sense about it being better to spin the motor than to bog it down.  Thanks for the tips!  Nice to hear from someone who's successfully been using it.

I don't use the gear shift sensors. Thought about it, but my riding style doesn't seem to need it. I just pause peddling for half a second before each shift.

Michael, thanks for letting me know you don't have the shift sensor installed.
Not having used the setup before I wasn't sure what to expect, so I figured better safe than sorry.
I know the brakes have a cutoff to the motor, so I considered using one as a sort of manual clutch to do the same thing during shifting, but the sensor was only $25 more so I figured I'd go with it.  
I'm guessing I would probably be fine without it.

The paint on the battery bracket is dry so I mounted it up to the bike using the water bottle bolts on the down tube and the seat tube.  It's not very noticeable in my opinion, and holds the battery like a glove.

Amazon says the motor will be delivered tonight, but since I work get up at 2am for work, it'll probably have to wait until tomorrow afternoon.

OH BABY!  It's fun!  :)

Did a quick test run last night with no front brake connected yet, and the wiring kind of loose.   I was impressed, but I didn't push it hard, just a quick test.

Today after work, I finished getting everything done (mostly) and took it out for a speed test.  
Again, I'm super impressed with how easy it is in the pedal assist modes.  1 is like a decent push and all the way up to 9 is speed demon.  Pedaling as hard as I could I got up to about 38 mph (the bafang computer read 38mph, and my phone's gps recorded 37.7mph.  Just throttle was anywhere from 30mph to 35mph depending on the wind and the ever so slightly rolling "flat" road I was on, I had to tuck down low to get those numbers.  Fully upright would be less.

It's really quiet, I actually don't really even notice it running.  It does kind of kick when it comes on, but nothing too harsh.

With twenty minutes of testing it, I'd say it's awesome, and everyone should get one!  Time will tell how it holds up, though, so the verdict is still out.

Installation wasn't difficult at all.  I watched a few youtube videos and it was monkey see monkey do.  

I still have to mount the battery properly by bolting it to the bracket, and I need to clean up the battery connection.  For some reason they went from a 12 gauge wire size to an 8 gauge wire size for the battery connector.  I couldn't get a yellow butt splice to fit over the larger wire so it's temporarily being held by wire nuts.  I'll have to find a butt splice big enough for the connection.

I'm pretty happy with the way the wiring turned out.  There's not much that can be done to hide it other than wrap it around the frame, and tie wrap it down.

Now I just have to go riding....

Got a little over sixty miles out of the first charge on the battery.  That was with a lot of heavy throttle, and over 2k feet of elevation up really steep climbs.

Just got back from a ride up to the state park behind me.  

Beautiful day for a ride, everything worked perfectly.