CAMPERVAN CONVERSION ELECTRICS
THE ELECTRICAL SYSTEM
A major part of any camper van conversion is the electrical system. Design decisions will affect how your van performs so it’s vital to get the electric system right at an early stage.
The main differences between campervan and household electrical systems are:
Supply: Household supply is pretty much unlimited so you can use as much as you like. In a campervan, you need to manage the supply and battery levels yourself.
Voltage: The voltage delivered into a house is much greater than in a camper.
Managing the supply and usage of electricity becomes a big part of van life. The campervan electrical system revolves around onboard 12v batteries. The batteries can be charged when driving, by solar panels, by hooking up to a mains power supply or by all 3. Campervan gadgets and appliances are powered by the stored energy in the batteries.
To design an electrical system to suit your needs, it’s essential to understand your demand for energy, power consumption, if you can store enough batteries to meet these needs and importantly, how to recharge them. Figuring out how much power you’ll use is the first consideration in any campervan electrical design. It’s the only way to have confidence the entire system will meet your needs.
The whole calculation can seem quite complicated.
Make a list of every electrical appliance and gadget you’ll use in your camper
Identify the amps each appliance uses. Some appliances state amps, others state the usage in watts. To calculate amps, divide the watts by volts. For example, an appliance is 6 watts, your batteries are 12 volts. 6 divided by 12 (watts divided by volts) is 0.5 amps
For any household (AC) appliances, multiply the answer by 1.2 to allow for the conversion costs of AC to DC power
Estimate the number of hours each day the appliance will be in use
Multiply amps (from step 3) by hours (from step 4) to calculate the total amps needed per day for each appliance
Add together all amps needed per day. This gives you the total amp hours per day you expect to use
Some days you’ll use more energy than others so add some contingency. We add 20% but you might want to add a little more or less for yourself. To add 20%, multiply total amp hours by 1.2
WHAT SIZE BATTERY DO I NEED
Batteries are measured in amp hours (Ah).
From the calculation above, you’ll know how many amp hours you expect to use each day.
But this is only half the story. What size battery you need to meet expected use depends on the type of battery.
Most batteries aren’t 100% efficient so don’t deliver 100% of their amp hours.
Roughly speaking:
Lithium batteries are about 99% efficient
AGM & Gel about 80% efficient
Flood lead acid (FLA) about 50% efficient
So to deliver 100 amp hours each day, a 100ah Lithium battery might just be enough but an AGM battery would fall someway short. A 100ah FLA battery won’t even provide half of the 100 amp hours needed so you’d need to at least double the battery size to 200ah. Our article on campervan batteries goes into a lot more detail about the different types of batteries and their advantages and disadvantages. And our battery bank calculator also works out what size battery of each type you need. Now you know how much electricity you expect to use each day in your campervan and the battery bank capacity needed to meet the demand. The next step is understanding how to recharge them. There’s no point installing a 200ah lithium battery bank if you have no way to recharge it.
CHARGING YOUR BATTERIES
Without an effective means of replacing the energy used, campervan batteries will flatten. Not only is it important to recharge them so you can continue to use them, but if left too deeply discharged for too long, their lifespan will shorten. There’s 3 ways of charging a leisure battery in a camper:
Charging batteries while driving
Campervan solar panel system
Mains hook up battery charging
CHARGING 12V BATTERIES WHILE YOU DRIVE
Vehicles have a 12v main starter battery fitted because they need energy to start the engine when you turn the ignition.
Main batteries give a surge of power (enough to start the engine) and they’re recharged from the energy generated by the running engine. If the vehicle’s electrics remain on long enough after switching off the engine, the start battery could end up flat so unable to restart the engine. Unless you only ever need an electrical supply in your campervan when your engine is running, you’re going to need a system a little more sophisticated than this. Most campervans have 12v deep cycle leisure batteries installed, designed for a gradual release of energy. It’s a separate set up to the main battery so you can start your engine, regardless of the supply available or voltage in your leisure batteries.
CHARGING WITH SOLAR PANELS
You can fit rigid or flexible panels to your roof, or have portable panels, propping them up when you’re stationary.
HOW MUCH SUN DO YOU NEED TO RECHARGE YOUR BATTERIES?
So this calculation is a little more speculative because the energy from daylight is inconsistent. The sun isn’t in the best position to deliver energy to the solar panels all day. Shade and cloud will interfere with the level of energy delivered too. So to try to keep it simple, let’s assume we get 4 hours of full sun daylight per day. Now we’ll calculate how many amps a 100w solar panel could generate. For each full hour of full sun, a 100w panel can generate 100 watts of energy. Our battery is a 12v battery. To calculate amps, we divide watts by volts. So our 100w solar panel could generate 100 watts/12 volts = 8.3 amps per hour. In our working example, we need to generate 70 amps to recharge our camper van batteries and at 8.3 amps per hour, we need about 8.5 hours of full sun on one 100w solar panel. If we have 4 solar panels each of 100w on the roof of our Sprinter so in theory, with full sun for a little over 2 hours, we’d recharge our 140 amp hour batteries. You can guess by now, the reality is somewhat different. Because of inefficiency of the panels and charger, the battery doesn’t receive all the amps delivered. These figures are for illustrative purposes. For a more accurate calculation check out our campervan solar calculator to size your complete setup.
CHARGING FROM MAINS POWER
Besides charging the battery from the engine, you can also use a mains hook up facility. By fitting a battery charger (also known as a power converter), you can convert the 240 v AC mains supply to the 12 volts DC needed to charge the battery. This allows you to plug the battery charger into the shore power and trickle charge the leisure batteries. While you’re hooked up, you can pretty much use electricity as you would in a house so you don’t need to worry about your batteries too much.
HOW TO USE APPLIANCES IN A CAMPERVAN
Electrical appliances use either direct current (DC power) or alternative current (AC power). Mains power supplied to typical homes and businesses is AC power so most household appliances run on AC. Generally speaking, any appliance powered by plugging it into a wall socket uses AC. Think about appliances like washing machines, TVs, microwaves and hairdryers – they all run on AC power. DC appliances tend to be less power hungry. Gadgets you can plug into cigarette lighters or USBs typically run on DC power. Because AC power cannot be stored, the camper’s 12v batteries provide all the power when living off grid. Using energy efficient 12v DC appliances helps reduce overall demand. 12v appliances for campers are widely available including LED lights, heaters, ventilation fans and even fridges so minimising AC appliances is easy. But what about running AC appliances when off grid? Most laptops, TVs, camera battery and power tool chargers need an AC power supply. Without hook up, battery’s DC power can be converted to AC by installing a power inverter.