To answer the OP's original question - No, not at all. The overall Batteries themselves are usually 36 or 48 volts and custom made to fit a bike frame - long and narrow and having proprietary contacts for a particular bike. Not suitable for solar work at all though you may be able to hack a solar charger if you know what you're doing.
Most of the other comments on this thread relate to the Cells that make up these Batteries.