Or would it take forever?
I don't really understand electricity & batteries so, if I bought something like these
https://www.sunstore.co.uk/Portable-Solar-Chargers/ would it charge the battery or would it take days? If I can which one should I buy?
Just asking as I like the idea of being a bit greener....
Sorry Kathymac, it's one of those good ideas that basically doesn't work. Unless there is a lot of input.
Those solar panels typically produce 12v DC voltage into a load . Let's say it was a 100watt panel, that means that it would under best sunshine conditions produce maybe 14 to 15 volts at a current of 8 amps. Best sunshine conditions are typically only about 3 hrs per day. There is power available at all the time the sun is shining but t can be pretty low.
Now the battery in your bike wants around 42volts from its charger to charge the battery properly. Therefore you would need a special electronic device called a DC to DC convertor to up the voltage from 12 to 15 v up to 42 and in doing this maximum current would drop to say 3 amps. So your battery could charge in 4 or 5 hrs.best case.
But those specialist devices are not usual and it is more usual to get a DC to AC invertor which would then mimic the mains supply. You would then use your mains charger with it... There has been some discussion on another thread here about possible damage to the bike charger from the output of some ac inverters.
When you add up the cost of these items, you would buy a large amount of mains electricity for the money. Now solar panel pv is great for those who need it. Boats, remote cabins etc. And led lights have made it a much more feasible option , but not a good idea when mains electricity is readily available.
A better arrangement is to go the full hog and get a full domestic 2kw peak unit fitted on your roof , and avail of whatever feed in tariff is available. Much longer life and basically a set and forget option, which will give real savings every day.