Van & Campervan Electrics
The Complete Guide

Designing the electrical system of a converted van or campervan is often the most intimidating step for DIY builders. Between Volts, Amps, solar power, and the risks of overheating or fire, it is easy to get lost. This guide brings together all the essential steps to help you design your 12V and 230V electrical system safely and correctly.

1. Calculate Your Electrical Load

Before buying any equipment or metres of cable, the first golden rule is to calculate your daily energy requirements. An undersized system will leave you without power in the middle of the night, while an oversized system will unnecessarily increase your budget and your vehicle's payload weight (MTPLM / GVW).

To calculate your consumption, multiply the power rating of each appliance (in Watts) by its average daily usage time (in hours). This gives you your total daily energy requirement in Watt-hours per day (Wh/day).

2. Choose Your Leisure Battery Technology

The leisure battery (or habitation battery) is the heart of your electrical system. Unlike your engine's starter battery, which is designed to deliver a high current burst for a few seconds, a leisure battery is designed to provide a lower, steady current over long periods.

AGM / Gel vs. Lithium LiFePO4

For decades, lead-acid batteries (AGM and Gel) have dominated van conversions. However, they have one major limitation: they should never be discharged by more than 50% of their capacity to prevent premature plate sulphation. In addition, a 100Ah AGM battery weighs around 30kg.

Today, Lithium Iron Phosphate (LiFePO4) technology has become the preferred choice. It permits depth of discharge up to 90%–100%, offers a lifespan of 3,000 to 5,000 cycles (compared with around 500 for AGM), weighs a third as much, and recharges twice as fast.

3. Generate Electricity: Solar & Alternator

To recharge your leisure battery and achieve off-grid independence, you have two primary sources:

• Solar Power: Rigid or flexible panels mounted on the roof convert sunlight into electricity. This electricity must be regulated by an intelligent device called an MPPT solar charge controller (Maximum Power Point Tracking).
• Engine Alternator: Using a DC-DC (B2B) charger, you can safely draw energy produced by the engine while driving to rapidly recharge your leisure battery bank without overloading your alternator.

4. Cable Sizing and Electrical Safety

This is the most critical step for your vehicle's safety. At 12 Volts direct current (DC), low voltage means high current flow ($A$). An undersized electrical cable (too thin) will resist current flow, overheat excessively, and create a major fire risk.

Cable cross-sections (expressed in $\text{mm}^2$) are calculated according to:

1. The maximum current in Amps flowing through the circuit.
2. The total cable length between the power source and appliance (round-trip distance).
3. The maximum acceptable voltage drop (strictly 1% to 3%).

5. Powering 230V Appliances (Pure Sine Wave Inverter)

If you want to plug in a laptop, power tools, or household appliances just as you would at home, you will need a 12V to 230V inverter.

Always select a Pure Sine Wave inverter to supply a clean electrical waveform that won't damage sensitive microelectronics. Keep in mind the initial startup surge of motorized appliances, which can draw up to double their rated power for a fraction of a second when switching on.