Introduction: DIY Electric Bike Conversion

About: Stan has a BS Geology, MS Civil Engineering and has worked as seismic geologist/geophysicist in the oil and gas field, a civil design and water resources engineer as well as a host of hands-on jobs. He has liv…

Here is how I used electric bike kits  to convert bicycles into e bikes. Only one e bike conversion is shown here.  

The bikes were older daily rides that needed work and new paint, so this was a chance to fix them up and install the kits all at once. 

Before you get started with a conversion, decide what you want to use as a donor bike, what kind of riding you want to do, the kit you want, and finally the cost. You may be tempted to just get the cheapest kit out there, which might work, but it is best to try and figure out what you want the final conversion to do. 

If you need help in deciding the size of motor and battery pack to use, cruise on over to: for details on how much power you need. It is interesting if nothing else. 

Step 1: The E Bike Kit

Here is the kit used in the conversions. You have a rear wheel motor, controller, thumb operated throttle, on/off switch, brake levers with kill switches (not used), and battery to control cable. 

The motor in this kit is a 500 watt continuous, 1200 watt peak power geared motor especially suited for hills. This motor requires a 22 Amp continuous controller. 

 The brake levers had kill switches on them. Since the throttle is thumb operated, the kill switches and extra wires did not seem necessary. This proved true later on. If you need to stop, you just let go of the thumb throttle, and the motor stops. It is intuitive.

The kits also came with nylon battery bags. These bags are well made, but the battery instructions warn against using these bags! Go figure. 

Cost of Kit: $350
Controller:  $  50 extra 
Total cost for the conversion including the kit, battery, and parts was about $950

Step 2: The Donor Bike

The donor bike needs to be a sturdy frame. It is said that cheaper bikes make good e bike frames. This may be true from the motor point of view, but if you want to pedal the bike too, maybe not such a good idea. 

I opted to use older mountain bike frames. They are steel, and heavy but strong and they are good bikes that roll well. The paint on the frames was chipped and not looking too good. 

 To improve the frames, they were stripped of most parts, sanded, masked and painted. This took about a day and cost about $10 for the spray can paint. The resulting paint looks good but is not as durable as the original factory paint. If you match the spray can paint close to the original paint color, a little scratch is not easy to notice, and can be touched up quickly. 

Step 3: Install Motor

Installing the rear wheel motor was pretty straightforward except for the shims, which proved to be some work. 

 The motor and wheel appear very high quality, durable and well built. However, they are an inch or so wider than the old rear wheel and the bike frame dropouts. 

 I just took the frame, placed it on the ground, and pulled it out a bit. This may not be the best way to do it, but It worked. Just watch out how far you pull as the frame will bend easier than you think and is not as easy to push back into original position. 

The kit only comes with one fat aluminum shim. As it turned out, it took 5 extra shims to properly center the wheel in the frame, and move the gears away from the frame. The gears will hit the frame if not shimmed out.

To see more on the process, go to:  

Step 4: Install Switches

The next thing to do is install the switches. This is pretty easy except for removing your old handlebar grips, if you have them. 

One trick to removing old grips fairly easily is to take a screwdriver and pry open the grips, and then pour some soapy water into the opening. Wiggle the grips around (you might need a pair of pliers or vise grips) until they break loose, pour in more water and so on. 

Before you take your old gear shifters off, look and see where the switches will be mounted. The thumb throttle lever on the kit described here was a little short, so you want to get it as close as possible to the gear/brake lever as possible. 

The on/off switch can be easily mounted on the other side. 

  After mounting the switches, carefully dress the wires back to the motor area. Make sure to leave a little slack around the headset/headtube of your bike. This is to allow the handlebars to turn freely from side to side. Attach the wires to the frame using zip-ties supplied with the kit, or get some at Home Depot. 

Step 5: Install Battery Box

The next thing to do is to decide what kind of battery box you want, measure your battery and controller, select the box, drill some holes, cut a wire opening, and install the box.

 1. Decide on a box. This kit is powered by a 36V 15AH LiFePo4 battery. Instructions with the battery say do not drop, dent, or otherwise injure the other words, protect it. I decided on a hard plastic box, but later switched to metal. The instructions further recommend padding the batteries in foam.

 2. Measure carefully how much room you need. The box used here is made by Buddy, 12-3/4" x 8-3/8" x 6-1/2". Two of them delivered from Amazon cost about $41. They have locking tops which is good for some security at least. The down side is extra weight of the metal. 

3. Ours were mounted on rear bike racks. I took the racks off of the bikes, turned them upside down, marked the holes and drilled right through the rack(s) as needed. Then bolts were just inserted. One thing to do here is put some glue (I use Goop) on the threads since your bolts WILL otherwise work loose under vibration.

 4. Cut a slot for the wires. Remember the wires you carefully dressed to the back? Cut a slot about 1 inch deep and 1/2 inch wide for the wires. I cut this slot at the top of the box using an angle grinder and moto-tool. The lid can still close over the wires, and they can run across the top of the battery to the controller. 

 5. Drill the controller holes. Measure and cut 2 holes for your controller just like you did for mounting on the rack. Be careful not to drill the controller!

Step 6: Line Box

Line the box with foam or other insulator of your choice. We just happened to have some old foam seat cushion lying around. It made great padding. A piece was glued to the top inside of the box to make it easy to open the box for charging. 

 The bottom line here is to make sure the battery is padded, that there is room for the wiring and in the case of the metal box that you make sure there are no bare wires/connections that could short out to the box.

 Note the position of the controller in the back and the battery in front. This is in case of a fast stop, the circuit board on the back end (nearest the controller) will suffer the least.

It is hard to tell, but there is 4" of foam (compressed) under that battery.

Step 7: Finish and Test

Well, this is the beginning of the fun! 

After the kit is installed, be sure to road test it. The gears on the new freewheel probably need adjusting, as well as the rear brakes. 

After taking on a few rides, we were delighted to find that in spite of the nearly 60 pound weight of the E Bike conversion, it was very easy to pedal around as well as use the power. 

The more you assist with the pedaling, the greater the range. Either way, the conversions so far are great!