I've read War and Piece on such over the last twelve months and in the end there's only one way to find out turned up today even on our bathroom scales the original battery comes in a 3kilos and the lithium can barely move the needle but hopefully I'll get them weighed properly tomorrow and having loaned out my tester I'll check the voltage( it tells you too on the clues) as well before fitting,it looks like and interesting learning curve.