Electric assist bicycles and trailers

Hi Steven,
I am interested in electric assist bicycles and trailers. I think we're going to have to do a lot of adventures and work with them. Do we currently have batteries that could help an electric bicycle, say, pedaling 2/3 of the time go 20 miles, pick up something 50 pounds, and return for a recharge to home? I am interested in how much distance, hill and weight we could take and still get back home for a recharge.
Thanks,
John S
PDX OR

Electric Vehicles NW has a really great overview of what electric bikes are capable of:

http://www.electricvehiclesnw.com/index.php/list-info/electric-bike-selection-guide

I bought my first electric bike from them over a decade ago and they really know their stuff (especially about how these bikes perform in the hilly PNW)