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Dirt Cheap DIY eBike

wturber said:
Why not just look for a used e-bike wheel hub motor? Adapting some other motor can add complexity and cost just figuring out how to mount the motor and get power to the wheel. I pickup up a 36v hub motor locally for less than $50 mounted inside a 20" wheel.

There are also possibilities in bikes like this ...

WOW! AMAZING! I would buy that in a jiffy, working or not. There are never deals like that around me :(
Actually yeah, when i first started out, i bought a few supposedly dead ebikes. They just needed a new part or two.

That was cheap, but i was bored with them in a few days.
But prebuilt bikes were a lot crappier in 2010! we're talking 250w motors everywhere.
Finally have a potential motor for the eBike! Along with a sprocket for the rear wheel.

I'll have to figure out a way to make the two work together. As they are, they're not compatible. I've also made a purchase of 25 batteries, or 100 cells total. These are modem backup cells, Samsung ICR18650-22F and are rated for 4.4A continuous discharge. This way I'll need 60-100 cells for the eBike instead of the 200-300 laptop cells I would have needed.

And so, my testing station is back in service. Pay no attention to the red cells. They're not for this project. :)

I'm a little ignorant about some aspects of electric motors. This starter motor was designed to be used at something like 11-14V in a car, and use something like 400A I guess? I haven't found the exact specs yet. But that works out to 4,800W. At most, I'd be putting 1,600W and 140A into it if I use all 100 cells. I wonder if that will be enough to push the bike and I up hill? I'm also aware that starter motors are not designed to operate continuously. I wonder if there will be heat issues?. Maybe with the smaller Wattage, it won't be a problem. I've seen other eBikes using starter motors, so hopefully, mine will work out too. I also wonder if the Voltage could be increased to cut down on the Amps. I'll have to use some beaffy wires otherwise!
I'm not sure a starter motor is the best place to start. One thing you might look at that I've seen done successfully on YouTube videos is to convert a car alternator into a DC motor.

Starter motors are only designed to run for a few seconds at a time. If you run one at significant power levels for more than that, it may quickly burn up. (people kill starters in their cars by cranking them over and over for too long). You can add cooling systems but that's more work, money, and materials (and weight and volume added to the whole bike).

They also don't usually have bearings, but only bushings, so they also don't have a very long lifetime. You may be able to replace the bushings with bearings, but that's more work and money.

Most of the motors on a car are either intended for low power or low duty cycle, or both. Some things like alternators can be converted to motors, and has been done successfully and documented around the web many times, but most things can't be used straightforwardly.

A powerchair motor with gearbox would be a better option, as far as brushed motors go; they can be had in pairs for free or cheap if you find someone with a dead-battery chair they don't use anymore. Sometimes they're cheap at thrift stores. You can look at my CrazyBike2 thread's early posts for how one can use one to run a bike. Their disadvantage is weight (much of it from the gearbox), but if you want torque...I stopped using them because I kept ripping stuff apart and bending things on the bike. :lol: Could've been fixed by redesigning the frame to deal with it, but at the time I didn't want to deal with it anymore.

There are brushless powerchair motors too, but they're harder to find (I'm still looking for a second one).

It's usually cheaper and easier to find old ebike parts these days, than to adapt other motors for use on an ebike. (coming from me, that's probably quite a statement :lol: )
Well, I ended up with 132 of the same type of cell, all of which passed testing! The best 128 will get used in the new battery.

I finally took some actual measurements to see what kind of space I've got available in the triangular space in the middle of the bike. Since I've changed my plans, as well as the cells I'm using, I want to put the battery in the triangular section. I got lengths and angles, and It looks like I can make the battery fit.

Here's the new idea as to how the components will go in the bike:

I spent quite a while thinking of exactly how I want to wire things up. I want to use a PWM controller with a remote Potentiometer to control the current to the motor. I also want to use a momentary on switch to turn the motor on and off as I ride. Rather than routing the battery power to the handlebar and then to the motor, I plan to use a relay so I can put little wires to the on/off switch, and thick short wires from the battery to the motor.

Anyway, a diagram will probably make more sense than me writing about it:

Each cell will have a fuse, and the battery will have a fuse. I'll also be using a BMS. Not sure if the motor really needs it's own on/off switch, but I think I want to put a toggle switch somewhere.

I also made a lot of progress on the motor today. Maybe I'll make a video of it. More on that later...
Interesting project, are you going to modify the front of that starter motor? Running the solenoid continuously
would be a big power drain. Of course you know that,.. I just wonder how your going to change the drive gear.

Hope she works out for you,.. if it were me, I'd do like wtuber said and search the bay for a used hub motor,..
with patience you can find a screaming deal.

Anyway,.. I mostly wanted to say that lithium batteries are not something to take lightly,.. when you start wiring them
up, and connecting up your bike, make sure that you do it in an open area, preferably cement floor,with nothing around
or above that will burn. And don't put them on a charger and walk away, always be in the general area. FYI. :flame:

Good luck man! :)
I've always wondered if it's possible to use a Minkota trolling motor as an E bike candidate? 12v-24v, some have
good power, and are sealed from the elements. I see them in the pawn shop's for cheap all the time.
Come with a controller too.
I think this might be my first post here so if it is then Hi to all.
I have built a cheap ebike and I can confirm it is possible and a lot of fun. I posted some videos of the build on Youtube and the first is here.

Ali Bro's DIY E-Bike using car alternator, laptop batteries and cheap Chinese controller Part 1

If you don't mind doing 20 or 30 times the work it takes to install a kit then go for it. This bike worked really well but had major issues with weight and drag so I'm currently on my 2nd build, still using an alternator but this time with a chain going to the chain sprocket. The new build is here.

Ali Bro's DIY Ebike V2 Episode 1

I have the alti-motor more or less mounted now with only painting and final tweaking to do and I'm currently trying to sort the electrics. I'd like the brake switches to work properly and if it's possible get regen working although I'm aware it will give minimal range extension. Of course none of the connectors on the controller match the throttle or brake connectors so I'm replacing all the connectors at the minute.
Thanks! I will be watching the whole series.

I've decided to go ahead and make a video series too. The first couple will be if I can get the starter motor to work well enough to use on the bike:

The next video I'll upload soon. :)
+1 on forgetting the starter motor. Even some cordless powertool motors would be more appropriate. As far as car parts go, an alternator is just the ticket.
I know you say you already have the starter motor but it does look a bit weedy.
If you call around your local mechanics workshops there's a good chance you can pick up a faulty alternator for free. They will swap them out if the electronics fail but you don't need the electronics.
I picked up one this way after visiting three workshops.
Ok you guys, if the starter doesn't work, I'll go find an alternator.

In the mean time, I figured out the issue with the controller, and improved on some things, and made a bit of overall progress.
Originally, I was thinking that current was the primary generator of heat in these things, but after playing around with it, and reading stuff on the internet, it seems that the brushes are actually the main source of heat. That would mean that pressure from the springs, and the overall RPM of the motor would be the big contributors that I might be able to address.

Anyway, it's all in the next video:

By the way: I've heard from a couple people that my videos are too quiet to understand. I will try to address this issue in future ones. :)
Last video on the motor, at least for a while. Finally got to use it at 24V, and I'm happy with the results.

Waiting on some parts so I can move on to the battery. The cells are ready to go, but I've got to make sure the shape I have will fit in the bike, and none of the soldering has been done. Still need to get a BMS, and a way to charge it, build a box for it... Lots of details.
I'm another who fixed a string of broken bikes getting started. You discover there is often good reason it's broken. And often sound reasons they didn't fix them. Except there's better bikes now, though more worth the owner fixing.

So how are you getting starters and alternators free? If there's a real path you have to free parts maybe people could discuss that angle if they knew what you could exppect to find.

The old gas powered washing machines had 2 horsepower 2 cycle engines that people made little cars and motorcycles out of, such as the 'Maytag Racer.' I'd expect a motor from a washer today to be below that range, but an older one could equal it. Dryer motors are or at least we're 1000w. Then there's the issue of AC or DC, volts all the way to 240, serious research required. But if someone was replacing their machines, a gold mine of parts awaits.

If you try the alternator, the Greentime controller mentioned used to run a motor without sensors, you'd need to check if it still does.

Building from junk can be fun, but there's reasons it might not yield such a useful bike. Much like fixing those junk bikes I got my hands on.
Things are progressing well. As long as that continues, I have no plans to change what I'm doing. I just thought it would be fun to share. It could be helpful to, or at least a warning for, the next fellow thinking of doing something like this. I know they're out there. I've seen the Youtubes, LOL.
Steady as she goes Mike,.. you can only learn from experience, and ten people will have ten different want's and
opinions. The batteries are the main part of any E bike, and as long as you have those, the rest can be changed,
and experimented with.

I'm sure you can get this to work, and it doesn't hurt to try,.. not a lot of money is being spent here, so theres no
big loss. If it roll's down the road, and put's a smile on your face, it's all good! :)

Look's like that motor's going to be a toque monster though, so I'd beef up the rack on that side.

Keep on keep'n on. :thumb:
Keep her lit Mike!
It's a thing we say around where I live as an encouragement.
I love what you're trying to do and you'll have a load of fun doing it but a word of warning, make sure you read and watch as much as possible other peoples builds to avoid making the kind of mistakes I have. I have probably spent more on bits that either weren't suitable or weren't needed than it would have cost to buy a proper motor. If I added the bits I screwed up and my time I could have bought a complete kit with mega sized battery but where would the fun be in that. I've already built a couple of ebikes from kits and although it was fun and I learned a lot I had waaaaay more fun building the bikes with alternator motors.
Good luck with it and keep posting the updates.
RebelRider.Mike said:
Ok, y'all have made it pretty clear that you either don't approve of, or don't understand the point of, my project.

Or looking at the bigger picture on a few issues. https://endless-sphere.com/forums/viewtopic.php?f=35&t=98117#p1437186

As Alibro says there's a lot to avoid in the things you don't know. The nice thing about using the junk is putting it to use. Some people want to remind you to be sure it IS useful. Nobody's trying to put the weight of the world on your shoulders, but. . . .
Thanks guy, I really appreciate the encouragement. And I really mean that! :)
I definitely want to do a good and effective job, and I think I can do that with what I've got, or things I can get cheaply. Maybe I should keep track of expenses as I go...

Speaking of expenses, the one thing I just couldn't do cheaply was getting cells for the battery. Old laptop cells are generally just not up to the task unless you use hundreds of them for the Amp requirements. So I saved up (and borrowed a little) and got a box of used modem backup batteries. Between those and laptop cells I've been collecting, I have 132 good cells to work with.

I made a video on how I do the calculations for battery design in general, and the bike in particular. I used a screen capture app, which I haven't done before, so hopefully it turned out ok. I kept it as concise as I could, but I've got to warn you, it's not exciting stuff! LOL


I'll cover actual building and safety issues in a future video.
RebelRider.Mike said:
Ok, y'all have made it pretty clear that you either don't approve of, or don't understand the point of, my project.

It ain't a question of approving. I'm all for cheap. You don't see an expensive rack on my bike. You see a cheap one from WalMart that I beefed up. I buy my tires and other parts on sale almost without exception. But here's the thing. Going the cheap route can EASILY end up being more expensive when you head into uncharted territory. That's why I suggested the alternator. That area is better charted for making ebike and go-cart motors than is electric starters. But I don't pretend to know whether or not you can make the starter motor work or not.

As for ebay shipping, many of the kits ship free. Mine did. And batteries or one of the biggest ebike expenses. So saving on the motor isn't even necessarily the best place to focus when going on the cheap.

Trust me. Most, if not all, of the folks here are on your side. But many of the folks here have tried various inexpensive options and have found them to be a false or at least sketchy economy. In the end, after adding up bracket costs etc. I'm probably over $100 on my rack. So how much cheaper was it really?

I think most people are merely trying to nudge you into a direction that they think is more likely to be successful. I think most people are sincere in making suggestions that likely to lead you to a successful project - meaning a cheap build that works. That doesn't mean that they are right - though I would keep in mind the amount of experience that is being brought to you. Ultimately it is up to you to decide if any of the info offered is valuable or not.

I say keep posting. Success or fail, it adds to the info available for the next guy trying to build an ebike on the cheap.

BTW, I found this on Craigslist. Cheap ($50) and probably has a controller designed to work with it. One thing I've learned about trying to do something cheaply is that patience often (though not always) pays off.

Finally got my 3A fuses in the mail!
Still working on the next video, but in the meantime, I took a bunch of pictures.


Organising cells via repacker.


Ready to solder!


First two series are connected.


The tape is there to make sure I don't solder the wrong cells.


The left side is done. Now it's time for the right side, which will have fuses. Here I've got 3 of the 8 series done.


Done! Still waiting on the BMS, and I just realised I don't have any 8s balance cables. I'll have to order some. Soon it will be time to build a protective box.

In other news, I have 2 fans, 2 heat sinks, and some thermal compound for the motor. I'm also putting together a cowl to move the air across the heat sinks more effectively. It looks like the freewheel I bought will be adaptable as well. I have an unrelated project I need to finish up this month, before I can work on that though.
Here's part 6: An intro to the bike I'll be using, a ton of battery design, and a little about the actual real life battery I made.

The BMS board is finally in the US, so I hope to get it next week some time. I've also got connectors, threaded rod, shrink wrap, and nylon bits. I'm about ready to start building the box!