My maths has it at approx 10,000 cubic inches of battery weighing in at 450kg, which rought and dirty is a 43 gallon tank (I may be way out) which is around 120kg of petrol.

Looks like standard is around 26 gallons (up to 36) so not miles away on volume, call it 1.5x. Wight and how you distribute it are going to be the real issue here at 3.75x the density.