F submitted this idea :
I've SORNed my car as I'm not going to be able to drive it for a couple of
months. No doubt the battery will eventually need a charge but do I really
have to disconnect it as current [pun not intended] advice seems to indicate?
If I do, I will, no doubt, have a whole lot of setting up to do on the
various electronics.

It's many moons since I last charged a car battery and at that time I just
clamped the charger leads on and let it get on with it.

If the charger is a modern controlled charger, no problem - just
connect and charge despite the warnings. I would not leave it
permanently on charge, even though the charger instructions might
suggest you can do this. Initially bring it to a fully charged
condition, maybe 24 hours, then every month or so repeat. That assumes
that your car has no major sources of discharge/faults - It should
discharge at less than 50mA-ish, depending on the model and its age.