Motor Size And Battery Size
 

Can I put a relatively small electric front hub on a bike, but put a 48 volt 20ah lithium battery with a contoller that will not burn the smaller hub up? I want lots of pedal assist distance, but not lots of weight and power that wants to twist my front forks off. I see a beautiful Raleigh step through frame bike for sale, but it has those two piece shock absorbing forks. I'm thinking I could put EZ trainer training wheels on it. I could pedal my skinny old boney butt all over the countryside.

Sure you could. 36v is probably better for what you want. any reason why you mentioned 48v?

Keep in mind if the fork has an aluminum bottom end (as most do) it is not designed for any kind of shock load at all. so something simple like spinning a wheel could snap the fork and cause a bad crash. Steel is the safer way to go.

The primary reason, AFAIK, for increased voltage is more speed. Agree with chas that you would be better served with 36V. Almost all bottom legs on suspension forks are aluminum as he stated, but should they be steel, make sure that you accommodate the "lawyer tabs" with "C" washers.

48 volt??? Just sounds bigger and like it would give more range. And I am just starting to learn about ebikes. Just an hour ago I read that riding my trike with the Nexus 3 speed up steep hills will ruin the Nexus as well as my legs!

Will fork supports allow an electric front hub to be used on aluminum forks?

I am thinking that I need to use the trike around my little town for strength training and snow and ice, and buy a women's bike with a low step through, lots of gears, and a steel fork, put spring action EZ trainer training wheels on it, THEN a front hub kit!

The more I ride that trike, and the stronger I get, the less I want to be stuck with it. Yesterday I saw another old geezer like me with a brand new nice looking womens bike. I may be motivating some old folks, zipping arund town. Everyone knows I have a hard time walking, and there I go, buzzing past!

36 volts is enough. Okay. I will find out what "C" washers are. Steel forks.

That is cool! Yes 48V has 33% more power than 36v, but using more power means less (in general).
Voltage = speed
motor current = power
battery capacity Amp Hours = range.

If you want more range you need more amp hours in the battery. If you use more current and/or more voltage in the motor, your range will go down (or you will need a bigger battery to keep the same range).