Simon Hobson ) gurgled happily, sounding
much like they were saying :

Well, Lithium is about half the density of water, so taking a
previous posters estimate of 600Kg, thats about 300 litres of water,
approaching 70 gallons of space, 5 petrol tanks, plus the cooling
space required, say another(6th) petrol tank.

Oops, 600kg is 600kg, which would be 600l of water. If Litium is half
the density, then you'd need twice the volume for the same weight, so
1200l of space - 4 times the sizes suggested above.

600kg is also roughly the kerb weight of any one of the majority of my
"fleet" of petrol powered cars.