[Thor84]

So has anyone ever done or seen a bigger fuel tank installed in an i30. Also a dual battery system installed I’m thinking in the boot? 

[Shambles]

Interesting questions. I can see the reason for the larger fuel tank but twin batteries...?

A 2000W sound system?  Microwave oven? 

[The Gonz]

The added mass of an extra battery will reduce your range.

[Thor84]

I was thinking an extra battery for Engel fridge and just to have in case on the open road something happens. Just curious more than anything.

[The Gonz]

So 'long range' is evolving to mean 'endurance', 'cross-country' or 'self-sufficient'.

In my day job I designed a similar thing using a military Landrover 110. One thing my design included was a solar collection/regeneration system featuring flexible, roll-up, foldable solar panels.

That may be closer to your aspirations.