$200 DIY Ebike Conversion

[BicycleB]

I know nothing about this topic, but the author of the article below started building ebikes a decade ago. Saddened by the failure of costs to come down enough, he converted his personal bike using off the shelf components (and one custom aluminum housing). Sharing in case it interests someone. :)

https://spectrum.ieee.org/electric-bike

[uniwelder]

I'm definitely interested.  I have never thought about using power tool or lawnmower batteries for the bike, but I really like the idea.  The front/rear brake procedure sounds a bit wonky, so I wonder how much money it saves to use the system as described vs an off the shelf throttle. 

I've been thinking about building an e-bike because we recently moved to a house where biking will be possible, even though the terrain isn't friendly.  From our house, its a 400 foot elevation change in the first mile.  Pedaling isn't fun (but definitely a good workout) for that part and braking feels dangerous.  Having regenerative braking would be a big boost, not because it'll help recharge the battery (though that is nice), but because it won't put so much stress on the braking system.  I've felt I need to upgrade to disc brakes, but hoping the energy suck from the recharge would mitigate that.

edited to add--- I"m getting really confused now that I'm reading through the procedure and clicking on the link for the motor.  The one that is linked doesn't seem to fit his description at all.  It looks like the output shaft rotates and the casing is meant to be stationary.  I'd like to know what the opinions are for people that understand e-bikes, whether this guy's approach and write up make sense.

[Weisass]

Just gonna leave this here….

https://www.mrmoneymustache.com/2016/05/25/recipe-for-a-badass-diy-electric-mountain-bike/

[gooki]

Batteries are the only expensive thing.

Hub motor Q100R $80
Spokes $15
Motor controller $20
Throttle $10

So $125 for purpose built parts. That leaves $75 for batteries. You're not going to get a great bike battery, but might be able to pickup some used power tool batteries. Or roll your own from used cells.

[AccidentialMustache]

I'm not actually convinced regen is a good thing on an ebike. It doesn't seem to actually net you much of any range (unlike a car), you'll still use your brakes (regen isn't that strong) and worst of all it means you always have the motor drag if you are out of juice or don't want assist (or until the assist kicks on, if there's a delay between starting to pedal and assist firing up).

I say this as someone with a direct drive rear hub motor radwagon v1.

[uniwelder]

Just gonna leave this here….

https://www.mrmoneymustache.com/2016/05/25/recipe-for-a-badass-diy-electric-mountain-bike/

I read that article a long while ago. Thanks for reminding me again. However, his most simple build would cost $600 without battery, and then just gets faster and more expensive from there.

[uniwelder]

Batteries are the only expensive thing.

Hub motor Q100R $80
Spokes $15
Motor controller $20
Throttle $10

So $125 for purpose built parts. That leaves $75 for batteries. You're not going to get a great bike battery, but might be able to pickup some used power tool batteries. Or roll your own from used cells.

Have you done your own build with these parts or similar? I’m curious what you think of the final product.

[uniwelder]

I'm not actually convinced regen is a good thing on an ebike…. you'll still use your brakes (regen isn't that strong)…

Yeah, I suppose I need to find someone with an ebike that’ll let ride up and down the steepest section and get a good feel for it.

Edited to add— what % grade do you think your bike can handle if you did a controlled decent just with regen braking? I think the steepest section of my path is about 8% for a mile.

Edited to add again— https://gocarlite.com/electric-bicycle-regenerative-braking/ someone goes through calculations for allowable decent grades that allow regen charging. It seems to be between 4-6% depending on the type of battery and capacity. Along with all the other downsides, I’m understanding why it’s not very useful.

[gooki]

Batteries are the only expensive thing.

Hub motor Q100R $80
Spokes $15
Motor controller $20
Throttle $10

So $125 for purpose built parts. That leaves $75 for batteries. You're not going to get a great bike battery, but might be able to pickup some used power tool batteries. Or roll your own from used cells.

Have you done your own build with these parts or similar? I’m curious what you think of the final product.

My first build was with a q100f front hub motor, cheap controller, and a thumb throttle.

I opted for the high rpm motor in a 700c wheel. Put it on a single speed bike with a 36v 8.8ah battery.

40km/h with a range of 30km.

Was a lot of fun. I commuted to work every day for three years before I sold the bike. New owner was also very happy. Highly recommend. The only thing to be aware of it was designed for speed (not hill climbing) thanks to the high RPM motor winding.

I've been through many ebikes since and am back to a bafang hub motor, this time running 48v with a top speed of 55kmh.

[AccidentialMustache]

Edited to add— what % grade do you think your bike can handle if you did a controlled decent just with regen braking? I think the steepest section of my path is about 8% for a mile.

I live in the midwest, my idea of a grade is an overpass (interstate or rail). Most of those don't have sidewalk and I don't ride 'em. I would guess the regen wouldn't actually slow me down any appreciable amount. Air resistance will take over the majority of that duty past 15 mph. Being vaguely tucked/jacket zipped is vs upright(/standing) and jacket unzipped is probably more drag than the motor would be.

You can't use the bike's regen to come to all-but-a-stop from anything other than 5-7 mph, or it'd take forever.

The bike displays 280w during regen, but I don't believe it. I know what accelerating at 280w feels like (that's more than assist level 3/5, less than 4/5) and this isn't that level of deceleration.

[Artem_F]

That leaves $75 for batteries. You're not going to get a great bike battery, but might be able to pickup some used power tool batteries. Or roll your own from used cells.

I've built two e-bikes and 3 batteries. The first battery used old cells, which I thoroughly matched, etc, but it didn't last long. I won't recommend doing this because the price of brand new high quality cells bought in bulk is about $70 for 36V 330Ah battery. In any case, you will need either to solder these cells (not recommended though doable) or weld it yourself and for the latter procedure you'll need a separate device, which can be either bought for $100 or built for $10-15 (it will use a relay and a car battery). In addition, you will need nickel strips and BMS charger board that will add another $15-20 to the cost.

[Just Joe]

For the battery one idea could be 12V DeWalt after market replacement batteries. I recently bought two for my decade old drill for $25 or so online. There are wired sockets available too that allow you to snap them into a holder. Three of those might carry a 36V 250W ebike a fair distance on flat ground. Lithium is a better battery but aftermarket 12V NiCD might be easier.

I have two ebikes.

The first is a Jueshai 48V 500W rear hub drive with a "silverfish" battery that locks to the frame right behind the seat post. Unknown brand cells in the battery (Sanyo?) but they are 18650. It is the same bike that the delivery people use in NYC. It is approaching 2000 miles. No troubles aside from minor bicycle wear and tear i.e. tires/tubes/rear derailleur. We've upgraded a few little things - seat, handlebars, tires, added fenders, rear rack. ~$1200. I'd buy it again.

The second is a Bafang BBSHD 1500W middrive with a dolphin style 48V14AH battery on the downtube. 18650 Samsung cells. Bought the kit, installed it on my old mtn bike. Steep learning curve about bicycle components during that project.

Added commuter accessories and touring tires when the old knobbies wore out (quickly). I have over 3300K miles on it. ~$1200 invested. I don't intend to replace it at any point. I do wish the frame was just a smidge larger. I see lots of ready to ride ebikes that are very appealing to me but the pricetag is dizzyng and I don't like the proprietary nature of their batteries or components. 

If I was building an ebike that would be at risk of being stolen, I'd focus on a $50 ten speed, 250W drive, and some sort 12Vx3 DeWalt battery - or tiny Milwaukee "Fuel" (lithium) batteries that I could pocket each time I parked. Consider a friction roller type drive that is self-contained and easy to attach and remove.

My bike always comes inside with me at work, the other bike is locked up at our teen's school. No problems so far.

FWIW there is a long list of forums to read:

Endless Sphere is a great one.
https://duckduckgo.com/?q=electric+bike+forum

[Just Joe]

Also, don't overlook used ebike parts.

https://www.ebay.com/itm/165054163188

Just add battery...

[Car Jack]

I've been interested in building an eBike for years, but haven't pulled the trigger.  I really like the idea of using tool batteries because of cost, availability and connector configuration.  On the Youtube channel, Rich Rebuilds, Rich built a small "car" using a whole bunch of tool batteries.  His theory was that you drive for a while, then go to Home Depot with a bunch of batteries and the receipt and return them.  Then buy the same number of batteries.  New batteries tend to be half charged.  Yah, this was sort of a skit, but the car using these batteries actually did work pretty well.