I had a bit of an issue with my missus' car this morning with a flat battery as it didn't want to start. The long and short of it is I now now thinking of getting a jump starter pack. What's the view of the lithium boosters around, are they as good as or better than the older lead acid type packs? Will any of them crank my P38 diesel if needed as I would want to get one that covered all my cars?