I've got a solar charger for my ebike now.
So my solar PV panels charge by 24V deep cycle lead acid battery bank - which then charges my 36V lithium battery pack. By my calculations that saves me 9 cents in mains electricity a day - so no great $ saving, but it's cool to have a solar charged ebike.
One future setup could be to replace the lead acid batteries with a bunch of lithium ebike packs. I could have them all charged in a row on the bench and ready to be slapped into the ebike. Sadly - that's probably not a sensible setup. The lead acid batteries are a much cheaper way to hold a sizable charge in one location. Lithium is great if you need mobility. So - I'll probably stick with my current setup.