I have the same problem so also use a trickle charger. One question though is it necessary to disconnect the battery cables before connecting the trickle charger to the battery terminals
My 2009 XKR coupe is in pristine condition with the exception of the underside.
The chassis and various parts are just showing slight corrosion where the paint has peeled off .
Should I rub down and paint with red oxide or under seal as in the old days ! or is there a better solution ?