Basically i ran my battery flat last night, went for a big crusie to london and back . Then went to start it this morning and the battery is flat. So obviouslly the battery is fecked.

So i need a new one but as my battery is in the boot, due to under bonnet space and i have a high comp engine , the starter is gonna need as much juice as possible . So can i fit a big bastard diesel battery to it. Will this be dangerous in anyway (like wire meting) and will my alternator charge it alright? also will actually give any benefit?

cheers for any help , need some quick answers really so that i can go get a battery at lunch .