Q&A for How to Build an Inexpensive Electric Bicycle

Mid-drive motors are lighter than hub motors and make it easier to climb hills or start from a stop. They also make it easier to change your tires. However, hub motors are a lot less expensive, sturdier, and less hard on your chains. It all depends on your needs and preferences.

Yes, there are lots of kits on the market that allow you to easily convert a regular bike into an electric bike. You can get them online, from department stores, or from stores that specialize in DIY bike supplies.

You’ll need to secure a cordless electric drill to the bike frame so that the chuck is in contact with the rear tire, then connect a bike hand brake to the trigger on the drill with a bike cable. Install the hand brake on the handlebars. When you squeeze the hand brake, the cable will pull on the trigger of the drill and activate it, causing it to move your bike forward (at a very slow speed!).

Parallel. If you use series everything will die when one battery does. As an added bonus, the voltage will be the same in parallel!

Yes you can, but the speed will not be very good.

No. If you do this, put in a freewheel, or you're going to be very tired pedaling as fast as the motor spins.

It depends on the laws in your local area, but most places don't require a license under a certain speed and/or wattage.

You don't need pedals, but they can be useful to save battery life or to return your bike home if your battery dies. You can have both the motor and pedals working together to make a trip easier while still getting exercise.

A lot of electric bikes have PS (Pressure Sensitive) seats that are activated when you sit on them; others only turn on when you start pedaling.

No. You will have to put in a dynamo and wire it up to the battery. Even then, it doesn't charge that much.

It depends on the motor. Legally the bike has to go less than 20 mph or else it would be classified as a moped and would require registration, a license, insurance, etc.

An electric bike specific battery should come with a charger. Most batteries from name brand manufacturers will come with or have separate chargers available for the battery by the battery manufacturer. Electric bike specialty retailers also sell battery chargers with sophisticated features like fast charge/discharge, timed or metered charging, etc. Follow the battery manufacturer recommendations for proper battery care to get the most life from your batteries, and follow all safety precautions listed.

Maybe. There are “pedelectric” bikes that use a motor to supply pedal assist, and bikes that offer an option of a throttle in addition to pedal assist. A pedelectric bike will work as well as a regular bike if you remove the pedals. Some bikes with throttle require some level of pedaling before the throttle will engage, while others don’t. Many bikes with throttles will not reach their maximum assisted speeds without you pedaling along with the motor. Most bikes do not have a place to put your feet if the pedals are removed, which could be uncomfortable and dangerous. Depending on where you live, removal of the pedals may make your bicycle legally a motor vehicle and subject to those laws.

If you want a system to warn you of objects or road defects, these exist and are sold already, or can be engineered if you have the skills. Their performance may or may not be up to your standards -- even million dollar robots can’t perfectly identify and avoid obstacles all the time. If you want an automated system to avoid things, you are approaching the sophistication of self driving cars.

For someone without any of the components but with some tools and skills, costs for an electric bike that can compare to entry level commercial electric bikes can run around $500-1,000 to start.

The kit or method you use determines this. Some electric bicycle and kit designs are belt or even shaft driven and require no chain at all. A hub drive electric bike motor with throttle assist does not generally need to be connected to the chain to work in throttle mode. Most any pedelectric bike will require a connection between the crank set gears on the pedals and the rear wheel to have functional pedal assist. On a hub drive, electrical power to the motor is supplied through wires and not generally the actual chain. A “mid drive” motor will need to connect to the chain in order to work.

Yes, you may use it. The MY1016 motor is 250 watts, compared to the MY1018 motor, which is 450 watts.

The type of throttle used must be compatible with the control system for the bicycle. You can, with skill, create adapters or converters to make incompatible signals work, but if you just stick to whatever your controller can accept, you’ll be fine.

To function, an electric bike does not generally require a throttle unless it was sold with one or has a controller that needs to see a throttle and sensors to function. In general though, you don't need one. Some people like the feature for on-demand assist or cruising when they don’t want to pedal, but it's optional.

The recommendation depends a lot on what you plan to use the bike for and how you plan to ride. That said, I would recommend at least a 750 (if not 1,000) watt motor, and, if you want reasonable range, 48 or 52v cells with a minimum rating of 19ah. For shorter rides, you can use a smaller battery. Multiply battery voltage by amp hour rating to get battery watt hours. Divide the watt hours by the motors power rating to get a general idea of how many hours of heavy use you might get. I’d also recommend a mid drive as opposed to a hub drive, or to find a hub drive wheel rated to take your and the bicycle's combined weight.

Through Amazon or eBay. I don't recommend buying from places like Alibaba or the overseas outlets as they tend to send used (US) returns and kits that are defective.

The easiest motor to use is the one that comes with a kit. If you want to make your own system, buying a purpose built electric bicycle motor from one of the major name brands in the industry is the next best bet. Beyond that, you can use any motor that has compatible voltage to your batteries and controller, has a power output and draw that fits your specs, and can produce the torque required at the RPM you desire.

That largely depends on the size of your battery. Shorting a battery can cause fire or explosion, and at the very least can damage or ruin a potentially expensive battery. It is not a good idea to find out.

Yes, as long as you use a torque arm on both sides of the wheels, it should be okay for between 1000 and 1500 watts, maybe more if you have larger dropouts.

Given that you asked this question, it suggests that you are not familiar with electrics. As such, it would be easier to use a conversion kit instead of a motor, which would require you to know how to work with electronics and motors.

The battery will most likely affect how long the bike will go. Volt/watt usage is also important. So it really depends on how much power the battery holds and how much volts/watts you use.

It depends. That's certainly enough power for an electric bicycle, but it ultimately depends on how good at building things you are. If you're good at building things and know where to put the motor, etc., then go for it! If you have decent knowledge of how to work on a bike, buy a conversion kit, and if you don't, know how to work on a bike at all, buy a pre-made electric bike, or go to a shop and ask them to install the kit.