Graeme, it's an injected car, with a regular radio and the problem is not isolated to headlight driving. I can't find or think of anything that would be draining it whilst parked, but as I said, it's really only apparent after a week or so of driving when the idle and starting suffer. Once charged, it's perfect again. I don't know why the charge light doesn't come on, I guess it's like the low fuel warning light that I discovered was faulty by running out of gas. Cheers, Matt