This type of battery was around $700 --- 6 months ago...

http://cgi.ebay.com/48V-20AH-LiFePO4...item4cf45e78de


prices are dropping,..

I recently read a article that MIT engineers have succesfully developed a lithium based battery that can be fully charged in 30 seconds...they expect that technology to be offered to the public in about 4 years time.