The bob trailer attached to my recumbent is retrofitted with a 600 watt brushed hub motor.
I am using lead acid gell batteries 12v 12 AH X3 for 36 volts.
The nice thing about using the trailer is I am back to having my regular bike just by unhooking my trailer.
My intent was to use it for my commute from the house to my shop 20 miles one way with some steep hills.
It works well I pedal along with the assist and just use it on the hills, I have not run the batteries out yet even when I take the long way 33 miles.
I used to do it without the assist but I commute now more with it.
The bike and fairing are homebuilt carbon fiber the bike I made in 2003.