Jimk wrote :
I think I'd start putting it all right at the weekend.... may as
well disconnect it & (see if it will) charge first...


If it's one of those chargers, which will not charge unless it sees a
voltage from the battery, you will have to connect a battery in
parallel to get the charge going.

Best to get the battery on charge ASAP, the longer it is left, the less
your chances of recovering it.