Electric Bike AND NEW POWER SOURCE
Bill, looking at your bike and trailer emotion, I had a thought. Get the grandkids to crank a generator like the GIs did in the South Pacific? That could be easily recharged at Jack in the Box or the Golden Arches. )
You are right of course, battery power is limited on all vehicles. I have a friend who lived in Flagstaff with a Prius and his engine would have to kick in after pulling one hill. That is a pack of 1.2 volt 7AH cells making 210V approx.
Power density is the problem plus clean cell storage. (Look at my 6 Golf Cart Batteries in our motor home) Gel Cells have clean storage advantages and weight disadvantages. Ni-Cad is better, but still weight. NiM-H better but still the weight. Then Lit-Ion are the highest energy density, but way out of sight on cost. Lith-Poly are the cost leader in this field, but haven't seen them in any usable size for E-Bikes so far. Here is a paragraph on them from Wikipedia which is not copyright protected.
This type has technologically evolved from lithium-ion batteries. Ultimately, the lithium-salt electrolyte is not held in an organic solvent as in the lithium-ion design, but in a solid polymer composite such as polyethylene oxide or polyacrylonitrile. The only problem with this design is that doesn't work unless heated to above 50 to 60 degrees Celsius. The battery that is currently available is a hybrid design correctly referred to as a Lithium-Ion polymer battery. The flammable electrolyte is still present but held within the polymer. The advantages of Li-ion poly over the lithium-ion design include lower cost manufacturing and being more robust to physical damage. Lithium-ion polymer batteries started appearing in consumer electronics around 1996.
I thought as long as the battery question had been raised I would put in my 2 cents.
Easy does it, but do it!