Introduction: DIY E-Bike Out of Car Alternator

About: Being a science student i love to indulge in projects related to engineering as i love to learn things practically...

This alternator might seems like a regular one but in our previous project we have converted it into a powerful brushless motor the link to is given below.

Now if you look closely we have got a permanent magnet rotor right inside this car alternator and today we are going to use it to convert this bicycle into and electric one so with that being said its time to get our hands dirty.

Step 1: Making the Drive Mechanism

As we have previously converted this bicycle two times by using this regular chain sprocket that comes with the bicycles but for this time we are using set of these two pair of gear which is commonly used 125cc motorbike. these gear having 18 teeth and the bigger one having 72 teeth which will gives us about 4 time of RPM reduction to increase the torque 4 times.

For making these gear usefull for our bike we have to undo those rivits on big gear and drilled the holes for mounting it on the aluminium bush which will later join with the rear wheel.

Step 2: Motor Mount

In order to mount our alternator we have used 5mm thick metal strip and cutted in two pieces and welded them togther for securing both of the front mounting holes of our alternator.

Step 3: Main Frame Alteration

To mount the alternator plate to our bicycle frame we have cutted the rear wheel mounting plate in an angle to get the perfect gear working possition, so we have welded the mounting plate to the main frame. after welding we done some grinding in order give it a finish look but there is some bending in the frame because we have welded the main plate with rear plate and haven't use nay support so to give it a rigid and reliable support we have welded some vertical plade in order to rainforce all the weak point.

To protect our motor mount from rusting we just painted it using matt black auto paint.

Step 4: Mounting the Motor

So after finnishing up the motor mount we have mounted up the big gear on the rear wheel and the placed the wheel over the frame and then mounted our brushless motor using M10 bolts.

Step 5:

Now with the drive mechanism in place we need a brushless motor speed controller and we have got one here is water cooled ESC ratted at 200Amp and can handle upto 12 cells lithium ion battery pack which sums upto 10kw of power so we are definately going to have lots of fun.

These speed controllers need a PWM signal to control the speed of motor, we can do that using a servo tester but thats not a convinient way to control an electric bike. So we are going to replace the potentiometer over the servo tester unit with an electric bike throttle kit that provides a variable voltage to the servo tester exactly like the potentiometer while making things way more convinient.

Step 6: Battery Pack

To power this bicycle we custom built two of these battery packs. Each battery offers 12 packs in series with each pack having four cells in paralel. Both battery packs are going to be connected in parallel so that we are going to have a total capacity of 1500 Wh which is more than enough to power our bike.

To secure the battery pack we have maid the battery case using 10mm thick MDF which will provide the battery pack to mount on the seat.

Step 7: Mounting the Battery Pack

To mount the battery pack we have welded two metal plate on the rare side of the seat of our bike which will later clamp our battery pack together. Then we have painted it using matt black auto paint.

After the paint dried we have placed the battery pack in the place and clamp it using M5 bolts.

Step 8: End Results

To analyze the results we are going to use a wattmeter and a GPS speedometer now keep in mind that GPS speedometer was showing 7 km/h less speed compared to the speedometer of our car.

In the previous project we have tested this alternator with a 24in prop and it was just drawing a 1000 watts so I was expecting starting torque issues as we just greaed it down to 4 times but to my surprise there was no such issues and this whole setup has plenty of power.

The bike offered insane amount of power and as I tried pulling full throttle the bike started wobbling and the next three seconds were the worst experience of this whole built. I definately would have twice the number of bones on my way back home if I kept on pulling the throttle anymore.

The maxmium speed we were able to take this bike to is 70 km/h compensating the speedometer error and still there is alot more power left. To my guess it can easily touch 85km/h but better let it be a guess still if anyone willing to break his bones can test this bike for us we would be more than thankful.

The maximum power draw during these tests was arround 5 killowatts which was not a problem for speed controller to handle but after 14 kilometer run the motor was getting extremly hot.

We did a 2km lap with agressive throttle so that the average speed was 40km/h so we ended up consuming 23 watts/km which will give us a range of nearly 66 km on a single charge.

We did the same 2km lap but this time with moderate throttle and averaging at 30km/h so we ended up consuming just 15 wh/km and that provided us with a rannge of freaking 100km on a single charge.

Well its our third time converting this bicycle as we barely started with a geared brushed motor, improved the efficiency with a hoverboard outrunner brushless motor and now with the converted permanent magnet car alternator this thing has insane power so If you guys want more details about all those conversions and their pros and cons, let us know in the comment section below.

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