Ask on pedelecs.co.uk forum.

You basically have a choice of hub motor (front or back usually front), which involves a new wheel.
Or chain drive. Pros and cons to each. The chain drive kits have had problems with water ingress in the past, don't know if they are sorted yet.

One thing to definitely NOT skimp on is the battery. (& don't go 2nd hand on this unless you are sure of provenance). Cheap batteries are not really a saving. Buy the biggest battery you can afford, mount and ride with... (bigger batteries mean the battery is less stressed and so lasts longer before it wears out). You could build one yourself, but I wouldn't recommend it unless you have the right equipment and skills.

Don't look on endless-sphere.com then, you'll be well and truly baffled!!! (that's the US site for REALLY DIY e-vehicles)

On pedelecs listen to "flecc", he really knows his stuff.

Posted By: VictorianecoI guess, given my weight (120kg) a 1000w motor would be preferred?

Or not electrifying the bike and getting more exercise

Well under EU (&UK) law the motor power must not exceed 250w. But that's a pretty rubbish specification. 250W average? 250W RMS 250W Peak?
(and 250W peak isn't very powerful at all).

Also to class as an e-bike the pedals must be turning for the motor to be powered. (Older UK law allowed the use of a throttle alone, like on my bike ;-) )

The power assist must also turn off above 15mph.

And I think there is also a requirement for motor cutoff if the brakes are pulled, though many people ignore this one.

The law is an ass on these things.

Not sure on the food vs electricity thing, but if the e-bike gets you cycling more instead of driving it's going to be a net gain very quickly!

================================
An average sort of e-bike would be:
250-350W 36 V motor (hub).
36V battery 10-15Ah

There should be plenty of suitable kits on ebay! Don't get the ones with the huge (physical) disc motors, they are direct drive (i.e. not via gears) and require large power output to work well. Get a smaller hub geared one.

You can assemble a kit yourself with parts on ebay. You'll need:
A motor (assembled in to a wheel or DIY)
A controller (suitable for that motor)
Throttle/pedelec sensors
Brake cutout sensors
Battery + means of mounting it


Bafung (sometimes called 8fun) produce some good motors.
Ping is fairly respected for it's "duct tape" batteries. (http://www.pingbattery.com/). Put one in a pannier rack.
"e-crazyman" used to sell controllers and throttles but he seems to have disappeared.


http://www.ebay.co.uk/itm/Electric-Bicycle-Conversion-Kit-E-Bike-36V-250W-Motor-Speed-26-Front-Wheel-/311702879759?hash=item4892f07e0f:g:y0QAAOSwZQRYbWdb

Is the sort of thing for the simplest kind of conversion. Just add a GOOD battery.

The chain drive ones do offer a key advantage over the hub setup in that they drive through your existing derailleur gears, so potentially can go up hills better... no personal experience of these. Most e-bikes are front hub powered.

Posted By: Ed DaviesWhat's the fascination with voltage? Why does it matter? Same with power tools. Higher voltage just means lower current and more thinner turns on the motor coils for the same power so is only of rather specialist interest.

It's easier to run multiple cells in series than parallel. Less concern and complexity regarding charging and cell failure.

Posted By: djhIt's easier to run multiple cells in series than parallel. Less concern and complexity regarding charging and cell failure.

Right, but why a legal requirement to placard the voltage but not, say, the current capacity of the cells?

Posted By: Ed Davies

Posted By: djhIt's easier to run multiple cells in series than parallel. Less concern and complexity regarding charging and cell failure.

Right, but why alegalrequirement to placard the voltage but not, say, the current capacity of the cells?

Because if in reality all the manufacturers (that have any political influence) put their cells in series then it's probably a useful measure of power (or whatever they sell). The current is the power divided by the voltage so you know that anyway?

The power rating of an electric motor is usually a soft limit. The way electric motors work means that a motor will draw what it has to in order to maintain speed. So unless the power is electronically limited to 250W then the motor will try to draw more than 250W if asked to. This is how Tesla cars can deliver such blistering performance for brief periods.

https://www.diabetes.co.uk/bmi.html

BMI is meaningless without context, I hover around 15% bodyfat

I diy built my own electric full suspension MTB a few years back, I've done 3000 miles or so on it. It takes the ' can't be arsed with hills' part out of cycling which is a game changer for me. I absolutely love it to be honest. Where I live the hills are crazy long and steep and no fun unassisted.

For DIY , I think chain drive is better myself. Try searching for Bafang BBS02 crank drive as this is probably the most talked about kit, and the one I have. http://wooshbikes.co.uk/?cdkit

I spent several months trawling forums and mining information before I went ahead with buying the bits, as there is a heck of a lot of information available. Endless sphere is indeed a seemingly endless forum, but amazing for it.

As others have said the battery is v, important, but the size of it depends on your likely usage style. Don't buy a huge one if you only want an hours use at a time. Mine is only 10 ah at 48v but i will be saddle sore before its empty unless I hammer it. (Obviously the faster you intend to go the more power you use . Double your speed and you square the drag. Etc). Also the battery is expensive and has a calendar life regardless of size so it might be better to get one just big enouh and replace it in 4 or 5 years.

You can buy good quality batteries now as the global market for ebikes is exploding, no need to diy here unless you like that sort of thing.

My bike cost £1200 to build in total including the bike itself at about £350

Sorry, MTB - mountain bike ☺