Battery terminals

[Highlander]

Had a good run across the downs to Leatherhead. On reachingn home I lifted the seat to look for numbers punched in the bodywork - There are none. However I noticed what looked like a toad, yes a toad, on the + terminal of the battery. On close inspection this was crud. I have had this many times on most vintage vehicles but this was large. I just knocked it off and cleaned up with boiling water and greased up. I have a standard 6 volt system. I always run the car fully charged and have never switched to half or summer. Questions. 1 - What is the cause? 2. Is there a way of stopping this? 3. Does it matter? My lights are not bright (Toby will confirm!!) but I put this down to dull reflectors, 6 volts, and age. I do enjoy the VMR forum, Regards, Aye, Alister.