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If you’ve ever been enthralled by the idea of owning a sleek, easy-to-ride electric bike, you know how quickly that charm can fade once you see the price—they average between $2,000 and $3,000. Build your own, though, and the cost goes down significantly.

For those who have never considered an e-bike, know that they are both less effort to ride than a standard bicycle but still offer some health benefits. They can open up cycling to those unable to ride a bike due to the physical effort required, and allow people to travel farther than they could with pure leg power. Whatever your motivation is, you can transform a regular two-wheeler into an e-bike—and I can show you how.

Before we start, it goes without saying that you will need a bicycle. Beyond that, you can customize your project to suit your needs with a variety of components that will electrify your bike. The process will be slightly different for everyone, but while the exact steps may vary, the general method I used here will get you a decent, reliable e-bike for an affordable price. I’ll explain my choices in more detail within the step-by-step below, but we also have a guide about what you should consider when purchasing each part. If you’re starting from scratch, we recommend you read that first.

Stats

  • Time: 12 to 14 hours
  • Component and material cost: $340 to $360
  • Difficulty: Moderate

Components and materials

Tools

Instructions

1. Get ready to install the motor. There are a few types of motor setups available. Without getting into it too much (we hash out the pros and cons in our aforementioned e-bike gear guide), these include mid-mounted, side-mounted, front wheel hub, and rear wheel hub motors.

I chose a 250-watt side-mounted motor kit from L-Faster on AliExpress—side mounts are relatively simple to install and the cheapest of the options listed above. If you’re not sure where to start looking for motors, L-Faster is a good place to start. They have a wide variety of kits and you should be able to find one that fits your bike, or at least get a good start on your search.

  • Note: When you buy a motor kit, it comes with numerous pieces that will help your e-bike project come to life. Mine included:
    • The motor.
    • A motor mount (with mounting clasps to secure the mount and the motor to the bike frame).
    • A motor controller to change the motor’s output. This is the brain of the e-bike system and the lights, brake levers, battery, motor, switches, and throttle are all connected to this component.
    • A power switch and a throttle. The switch turns the e-bike system on and off and you gradually push the throttle with your thumb to accelerate.
    • A sprocket.
    • Friction pads, which provide a surface with a lot of grip so the sprocket can be mounted securely.
    • Friction pad plates, which provide a rigid surface and support the sprocket. My kit came with three, each with three bolt holes that allow you to fasten the sprocket to the friction pads and plates.
    • A headlight and an on-off switch.
    • A brake light.
    • Front and rear brake levers that each also activate the brake light.
    • Connectors for the switches, motor, and battery.
  • Pro tip: If you get an L-Faster side-mounted kit like I did, replace all of the kit’s bolts with bolts from your local hardware store. The kit itself is generally high-quality, but I found the bolts stripped easily.

2. Mount the motor. Turn your bike upside down, resting on the handlebars. I had to take the rear wheel off to complete the motor installation, and you will too. Once it had been detached, I slid one friction pad into the center of the wheel, behind the spokes on the side opposite the gear cassette, then put the other one on the outside of the same side. Next, I put the friction pad plates behind the inner pad and the sprocket on top of the outer pad. (From the outside in, the layers should be: sprocket, pad, wheel spokes, pad, plates.) Then I fastened the sprocket onto the wheel, using the bolts, nuts, washers, and locking washers that came with the kit, and slid the chain over the sprocket (aligning the chain comes later). I set the wheel back in place on my bike, slid the motor bracket over the rear axle bolt, and began to tighten the left rear axle nut.

When the nut began to tighten, I adjusted the bracket so the bolt holes for the motor lined up in a way that the bolts could go through and allow the mounting clasps to fit tightly around the frame. While I could still slide the motor and motor bracket around, I put the chain over both the sprocket and the motor. Then I made sure the motor was positioned so the chain was straight, and tightened the axle nut. Finally, I bolted the motor on by pushing the bolts that came with the kit through the bracket and the threaded clasps, and tightening them.

An electric motor mounted on the rear wheel of a bicycle, turning a regular bike into an e-bike.
If you choose a side-mounted motor too, your rear wheel will end up looking something like this. William Elcock

3. Prepare the battery box. You can store batteries in a frame bag that hangs from the bicycle’s top tube, and if you want to do that, you can skip or adapt this and the next two steps to fit your needs. I, however, chose a waterproof, lockable ammunition box for added security. Your battery is precious and you’ll want to protect it from theft and the elements, after all.

Drill two holes, about ¼-inch (5 millimeters) apart, in each of the four corners at the bottom of the box for the cable ties that will secure it to the rear rack (eight holes in all). Then, test-fit your batteries and motor controller inside the box to see where all the wires that connect the battery to the motor, headlight, brake light, main power switch, and an on-off switch for the headlight should go. Finally, use a sharp box cutter to cut a rectangular hole into the left or right side of the box (depending on how you plan to run the wiring).

4. Secure the battery box to the mounting rack. You may already have a cargo rack on your bike, and it’s a good place for the battery pack of a DIY e-bike. I mounted my battery box on a rear rack. There was a tradeoff I had to consider: putting the box on the back meant my bike’s stability would take a little bit of a hit, but building a decent waterproof frame-mounted solution for a better center of gravity would’ve been more complicated. Now that I’ve been riding my bike for a few months, I haven’t noticed a huge loss of stability. The bike is heavier because of the batteries and the motor, but that doesn’t matter when you get moving—it’s only an issue when you have to lift up your bike.

Once I turned my bike back over, I secured the box to the rack using a cable tie threaded through the pair of holes in each corner of the box and around the tubes of my cargo rack. I ended up with the box running along the length of the rack.

5. Put the battery in the box. I was able to buy four used 72-watt-hour 36-volt battery packs from IMGadgets in Canada, where I live, for about $60. I chose the voltage to match the motor’s voltage and tested the packs before using them—they were in excellent condition. Finding used batteries is a great way to cut costs, but you’ll need to ensure you buy from a reputable seller, and/or one that lets you try them out before any money changes hands. You can purchase cheap batteries online, but you’re more likely to get safe, well-functioning batteries at a good price from a local supplier. Still, AliExpress and Battery Hookup are good places to find quality, affordable batteries online. Whatever you get, it should have a battery management system (BMS) to ensure each cell maintains the same capacity. This ensures uniform performance and battery drainage.

Before putting the battery module (all four 36-volt packs) into its housing, I ran a strip of double-sided mounting tape along the bottom of each pack and across their left side to ensure they wouldn’t bounce around while on the road. I used Scotch-Mount Extreme tape because it’s rated to hold up to 30 pounds—multiple strips was more than enough to keep my batteries in place. Finally, I placed the module into its home, pressing to adhere the tape to the bottom and side of the box. Where you apply tape can vary depending on the shape of your battery. Just make sure to cover as much surface area as possible.

  • Note: A battery’s watt-hour rating tells you how much energy it can store. Try to find one that has a capacity of at least 300 watt-hours. This should give you a range of about 15 miles (24 kilometers), because every mile (1.6 kilometers) should use up about 20 watt-hours.

6. Install the remaining components. With the motor in place, I installed the front and rear brake levers, the headlight, the power switch and throttle assembly, and the headlight’s on-off switch. For the brake levers, this was as simple as removing the old levers with the correct Allen wrench, fitting the new ones, and tightening the provided bolts. I fit the headlight, headlight on-off switch, and the power switch and throttle assembly over the handlebars in suitable locations and tightened them with the provided mounts and Allen wrenches.

Once those pieces were in place, I put my e-bike’s “brain” (the motor controller) on top of the batteries in the battery box and mounted the battery box and cargo rack to the bike frame. Finally, I attached the brake light to the cargo rack with a couple of cable ties. Where you put the “brain” depends on the remaining space available in the battery box.

  • Pro tip: If you had to add a cargo rack to your bike, add some locking washers. After some time riding the bike, the rack may shift position due to the weight of the battery, and locking washers should help mitigate or prevent this.

7. Connect the wires. I ran all the wires for the brake levers, on-off switches, lights, and motor through the rectangular hole in the battery box and connected them to the motor controller. Then I secured the wires to the frame with cable ties, but I had to do a little more work getting my charger sorted out.

The motor controller in my kit had an attached charging connector, and my charger had a male barrel end, so I had to wire a female barrel connector or they would not have linked up. This was relatively easy since the kit came with extra connectors. I just pushed the wires from the barrel connector into the metal tabs that came with the motor kit’s extra connectors (positive terminal to positive terminal and negative to negative), squeezed them together with pliers and pushed them into the connector that would eventually clip onto the motor controller.

  • Note: When buying a charger, it’s critical to get the right voltage. The voltage of both the battery pack and charger should match the voltage of the motor, and the motor will tell you what this number is. If you aren’t sure, you can also calculate the charger voltage by multiplying the number of batteries in series in a module by 4.2. This means that if your module has 10 batteries in series, you will need a 42-volt charger. 

8. Finish the project. With everything in place, I used a silicone sealant to fill the rectangular hole in the battery box that I cut out for the wires to completely seal it off from the elements. Finally, I installed a luggage lock to keep the batteries safe and further secured the battery box to the cargo rack with my ratcheting straps.

How the bike has performed so far

After completing the project, I took the bike for a spin. This is by no means a fast kit, but it has decent acceleration and can reach up to around 12 mph (20 kph), according to the manufacturer. You can ride the bike under full electric power by pushing the throttle and not pedaling, or you can pedal and use the throttle at the same time. Full electric is lots of fun and requires no effort to go relatively fast. It’s definitely a rush accelerating from a standstill and just cruising on battery power, but pedaling will extend your battery life. There is no automatic pedal assist with this kit, but that just means you’ll have to decide how much motor power to add with the throttle when pedaling.

A DIY e-bike converted from a regular bike, plugged into a wall in a garage and charging.
When you’re done riding, just plug your bike in and it’ll be ready the next time you need it. William Elcock

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