On my 455, I use (and would recommend) a desulphating trickle charger - mine is made by BatteryMinder, but there may be others. Mine comes with a set of leads that you connect to the battery, terminating in a plug, which you lead out through any convenient gap in the bodywork. You then simply connect the charger to the plug, and plug the charger into the wall - it couldn't be simpler.
Tim
Tim