Inverters and Mains Power

Inverters and Mains Power in Overland Vehicles

Modern overland vehicles often combine both 12/24-volt DC and 230-volt AC power systems. An efficient and safely-installed mains power setup allows you to run domestic appliances, recharge devices, and connect to shore power at campsites. This page outlines the principles and best practices for designing **on-grid** and **off-grid** mains systems using inverters, chargers, and safety equipment.

Overview

Vehicle electrical systems normally operate at 12 or 24 volts DC, while household equipment expects 230 volts AC (in the UK/EU). Bridging these two standards requires a power inverter — an electronic device that converts DC battery power to AC mains voltage.

Depending on your travel style, your system may need to support:

• **On-grid hookup:** connecting to campsite or home mains supply via a shore-power inlet.
• **Off-grid power:** using an inverter to provide AC from your batteries, recharged by alternator, solar, or generator.

Core Components

• Inverter: Converts 12/24V DC to 230V AC. Choose a pure sine wave type for compatibility with sensitive electronics. Common sizes range from 600W (for laptops and chargers) to 2000W+ (for kettles, tools, or induction cookers).
• Battery bank: Deep-cycle AGM, Gel, or Lithium (LiFePO₄) batteries supply the inverter. Lithium systems provide higher usable capacity and faster charging.
• Charger or inverter/charger: When plugged into shore power, a charger (or combined inverter/charger) replenishes the batteries and supplies onboard AC circuits.
• Shore inlet and RCD/MCB panel: A weatherproof inlet connects to campsite power. The line should pass through a Residual Current Device (RCD) and Miniature Circuit Breakers (MCBs) for safety.
• Transfer switch (optional): Automatically selects between inverter power and shore power, preventing back-feeding.
• Earthing and bonding: Proper grounding is essential. On-grid use ties the vehicle’s earth to campsite supply; off-grid inverter systems should bond neutral to earth at the inverter output to mimic a safe TN-S supply.

System Layout

Typical wiring order:

1. Shore inlet → RCD/MCB panel → AC distribution sockets.
2. Inverter output → RCD/MCB panel (through transfer switch if fitted).
3. Battery bank → Fuse → Inverter DC input (heavy cables, short run).
4. Charger → Battery bank (with DC fuse and isolation switch).

Use appropriately rated cables and fuses for all connections. The inverter’s DC side draws very high current — 100A or more for a 1200W load — so ensure short, thick cables and secure terminations.

On-Grid Use

When connected to campsite mains:

• Inverter may automatically bypass to charger mode.
• Ensure RCD protection and correct polarity.
• Use a tested EHU (Electric Hook-Up) lead with a waterproof connector.
• Avoid overloading — campsite breakers often limit current to 6–10A.

Off-Grid Use

When camping remotely:

• Turn off high-draw appliances unless batteries are fully charged.
• Prioritise energy-efficient devices: induction hobs, LED lighting, low-power fridges.
• Recharge from alternator, solar array, or generator as needed.
• Monitor battery voltage or state-of-charge display regularly.

Safety and Good Practice

• Fit fuses, isolators, and RCD protection on all circuits.
• Use marine- or camper-rated cables and connectors.
• Label mains and DC wiring clearly.
• Disconnect power before working on the system.
• Keep AC and DC wiring separate where possible.

Manufacturers of note

• Victron
• Renegy

See Also

• Solar Charging Systems
• Battery Types and Management
• 12 Volt Wiring and Fusing

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This guide is a general overview; always follow national wiring regulations (e.g. BS 7671) and manufacturer instructions when installing mains systems in vehicles.