12V Electrical System
Electrics are the most intimidating part of a conversion but follow a simple logic: battery stores energy, solar/alternator charges it, fuse box distributes it. For a weekender, a single leisure battery + basic solar is all you need.
Engineers walk through the full 12V system design. The most comprehensive tutorial online.
Start simple: a 100Ah lithium leisure battery + 100W solar panel + MPPT controller covers LED lights, USB charging, and a cool box. Total cost ~£300-500.
Always fuse EVERY positive wire as close to the battery as possible. Un-fused 12V wiring in a vehicle is a fire risk.
Use a DC-DC charger (not a split charge relay) if your vehicle has a smart alternator (most post-2015 vehicles do).
Label every wire as you go. Future-you will be incredibly grateful.
Plan your electrical loads: lights, USB, fridge, fan, pump. Calculate daily Ah usage
Size your battery bank (100Ah lithium covers most weekender needs)
Mount the leisure battery securely — it must not move in a crash
Install a DC-DC charger connecting vehicle starter battery to leisure battery
Mount solar panel on roof. Run cable through a waterproof gland to MPPT controller
Wire MPPT controller to battery (fused)
Install a fuse box / blade fuse holder. Run individual circuits for each load
Wire LED lights, USB sockets, 12V sockets from the fuse box
Add a battery monitor (Victron BMV or similar) so you know your state of charge
Test everything. Label all wires.
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