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Is this gonna be big enough for an electric bike? Answered

I have a complete, motor/wiring harness/controller/charger  out of a wrecked Spirit Scooter it has bad batteries but the motor runs.  I would like a 20/30 mile ride between charges 50 would be even better. The motor is 24v   250w  14a  How much of a battery system will it take to get the numbers I want or is it feasible?   I have a second one that is in great condition that just needs batteries. I don't want to molest it just yet.


250 watts is pretty weak. this would be a good setup for an electric skateboard, with a set of small batteries, like two 12v 7ah batteries from radio shack.

I seen where a guy used 2 of these together, I may try a trailer that pushes so I can use it behind several different bikes.

Really not a electronics guy so I would need some direction in doing this.

no, a trailer is a very bad idea. 250 watts is not weak enough, so your gonna hafta make alot of sacrafices, bieng range and top speed, meaning an electric skateboard would be an ideal project for this. also the electronics are easy, just battery to controller to motor. the hard part would be getting your chain drive right.

I don't understand why you would say 250 watts are not weak enough or is that a misprint?

I'm 51 almost 52 years old really don't want a skateboard I need something more practical.

well than theres prolly not much you can do with only one 250 watt electric motor. sorry bout the typo, that should read 250 watts is not strong enough. I would suggest giving this motor setup to a grandkid or neighbor so that they can make an electric skateboard, and purchasing a much more powerfull motor for your own electric bike conversion. for an electric bike, 500 watts is basically the minimum if you want to be able to get up hills. the only POSSIBLE, and possible bieng the key word here, e-bike conversion for this motor would be a friction drive electric assisted bike, but you would deffinantly have to be peddaling the whole time, and the motor would only be helping you a little bit, but if your dead set on an electric bike, that would be the only possible way it would give you any benefit at all.

I actually have 3 of those motors, 2 I know run the other is disassembled so I'm not sure of it's condition yet. I have 3 more motors that are in my robotic mower that I have no specs on but would assume they are a little stronger (more watts)

are those electric motors on your robotic lawn mower old powerchair motors? I think I saw an instructable on here about a robotic mower utilizing powerchair motors. if they are, than look at my instructable for instructions on how to build an e-bike. I used a powerchair motor for a fully electric conversion, and it works just fine. If your still in doubt as to wheather or not the motor will work, just do an electric friction drive. it's really easy to do, and if the motor isn't very powerfull you can just take it off and your not out anything. I am actually going to be constructing a friction drive e-bike soon, so if you like I could try to do an ible to help you out.

Here's a link to the Robotic mower I have, scroll down the page a ways and you can see the motors, unfortunately there are no specs on them but they look powerful http://www.robomower.biz/forums/viewtopic.php?p=313

ya... those don't look that great, and size isn't a very good indicator of power anyway. I would stick to the 250 watt scooter motors, and put one of them on the rear wheel with a 1.5 inch drive peg and the other on the front wheel with a 1.5 inch drive peg also. Then I would wire them both in parralell to a 24 volt source with a light switch. I think that this should be enough to get you moving. for the cells I would use two 12v 7AH cells from radio shack, they're about 45 USD a piece. For the pegs, I would purchase some 1.5 inch D alluminum stock, and rough up the outside alot with a hacksaw and a center punch to give it more traction. Then find the exact center and drill a hole big enough to fit over your shaft, then drill 2 holes for set screws. If this is not clear enough I could explain it a little better, but it would help if you could upload some pictures of your motor, maybe laying next to a ruler so I can judge scale.

The ones you see are not mine, just an example of what I have in the robo mower.

The original battery pack for this 250w motor was two 12 volt 12ah-20hr

sounds good. use those if the batteries will still hold charge. are you having trouble uploading photos? if I could see some pictures of the motors, especially the shaft I could give you a lot more help, possibly even give you a step by step on construction and peg mounting.


8 years ago

Check out the electric flat tracker (and others) over in the right hand column of this page.


8 years ago

The motor should be OK with the right gearing. You need to work out what RPM you need and expect the motor to be most efficient at perhaps 2000 - 3000 RPM.

As for range it depends on how you use it. If you only use it to peddle assist you will get a reasonable range. However you will need a substantial battery pack. Using 2 x 70 Ahr lead acid battery our racing car would do around 50 miles per battery set - averaging 28ish MPH.

This is pure battery power in a fairly heavy car. However these batteries are far too heavy to put on a bike.

You need to keep the C of G low so mount batteries in panniers low on the back wheel. You will need some kind of cut out to protect the motor from over current.

As long as you don;'t use the motor from a standing start a speed controller is not worth the effort and cost a simple on off button and suitable relay will work just as well and you can pulse the motor manually for lower speeds.