Using correct size cables for RVs is essential. Get it wrong and your fridge may not cool nor batteries fully charge for the entire life of your RV. Anyone sufficiently capable can legally cable RVs and cabins as long as no part involves grid voltage. This article outlines why.
Caravan & Motorhome Electrics
The essential handbook for anyone with an RV of any kind. Everything you need to know to make the electrics in your rig work for you.
Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.