Below I share my experience converting a regular lady bike to an electric trailer equipped bike.
This was intended to transport around 6 bottles of water (5 Liter/1.3 gallon each).
Step 1: The ideia
I wanted to adapt my mother's bike to allow her to ride her bike easier because her health was impaired. In the end of 2010 to buy an electric bike in Portugal was very expensive. The same applied to lithium batteries. So I started making some sketches using my Alibre CAD software; not well know in Portugal but more than enough for my skills at an affordable price.
Step 2: And some measures to manfacture
In these two drawings you can see some measures in milimetres based on the original bike. Actually the original bike was a slightly different one but around the same dimensions. As you can see my initial ideia was to have the lead batteries in the top of the rear wheel. The kit ordered was organized in a different way as you will see.
Step 3: The choice of the electric kit
Then surfing on Ebay, I selected an affordable (the most!) one, similar to the one in the picture but with batteries in the sides of rear wheel. I opted by the sealed lead batteries because of the lowest cost. They have a slight problem: are heavy like hell!
The specs are 24 V, 250 W. Because I ordered it from US, I paid a lot in Customs :-) I'll have the numbers in the end.
Step 4: The emotion is about to start!
I received my kit in the post and took it happily to my coutryside house where I installed it in the bike. As you can see the front wheel is totally from the supplier...the tire is a bit large so it was tight inside the front fork. It includes the engine.
Step 5: Installation of the batteries
The batteries supports were in the kit; only had to be installed in each side of the rear wheel. The most difficult was to arrange it with the fender and the rear support.