Cables for the solar are 10sq mm of copper (not plastic) which should be fine for 2.5 meters from panels to battery, the rest are even bigger.

When the body of the inverter is earthed it sparks quite badly, it's mainly the solar panels I'm concerned about. The inverter is definitely faulty, to try to get 240v to the entire van I plugged an extension from it to the outside plug and it blew one of the 4 40amp fuses every time.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.