Camper vans have always needed electrical power, either for running the lights, maybe powering the fridge or even powering the banging tunes from the stereo. Whilst you could risk using the starter battery and being unable to start in the morning, it makes sense to seek alternatives.
Some campers rely on 220/240v power via an electrical hook up, but many are looking for alternatives and with advances in batteries and solar power it is increasingly possible to be totally self sufficient. Solar power can be harnessed to charge leisure batteries and keep the lights on even when it’s dark and the prices of systems are falling. Solar is a simple DIY project for anyone to try. In this part we will look at deciding what system we need and then detail the specifics later in Part 2. So let’s begin…
Before we start buying equipment we need to assess our demands. If you want to maximise the life of the battery, you need to minimise the load. That doesn’t mean not having the luxuries you want, it simply means finding the low energy versions. For example, get rid of the old 12v halogen lights and fit LED equivalents. Consider fitting a 12v compressor fridge instead of a cool box. These fridges are super efficient and use minimal power, whilst at the same time chilling down the beer and even making ice for the gin and tonic!
Some will ask “can I use my hair dryer, or straighteners or my beloved 240v juicer?” In short the answer is yes, but you might not want to… If you want to be self sufficient and avoid mains hook up, the only way to provide 240v is via a device called an inverter which takes 12v DC from the battery and converts it to 240v AC. But and it’s a big but…. inverters are very, very inefficient and will eat your battery up unless you have something very substantial and even solar will be unlikely to be able to keep it topped up. If you absolutely must have it, then buy a Pure Sine Wave inverter as these are more efficient and use a little less power. In addition, if you don’t already have one, consider buying a split charge relay which will recharge the batteries every time the engine runs.
So once you have equipped your van with the latest low energy gadgets, you will then want to look at the size of battery and panel you need. Begin by adding up the power consumption of each device, normally measured in Watts (W). However to decide how big our battery and panel needs to be we need the Amps figure. There is a simple but necessary formula which will help with all electrical applications:
Power 
= Volts (V) x Amps (A)
This formula can be transposed provided you know any of the components and as our vans are 12v, we always know one element.
If we take a van with LED lights, a 12v compressor fridge, 12v Eberspacher heater and even a 12v Diesel Cooker. Add a couple of USB charging points and maybe an awning light. Looking at the labels on each item we should find either the Amps or the Watts and of course we already know the Volts. For the cooker and heater we must consider the start up cycle as this is the time they draw the most power. That said, once on steady state they use a lot less power, usually only kicking in as the temperature drops and otherwise only using a fan to circulate the heat and the air. Note that in hot temperatures the fridge will have to work harder and in the cold the heating will be on more. We use the formula above to get the total. We need to add up each item and assume a worst case of everything on at once.
From the calculations above you can see we need 50A to cover our needs. So we then need to look at the battery. Leisure batteries are deep cycle batteries commonly available in traditional lead acid, but increasingly in the more expensive modern technology LiFePO4 (Lithium) and AGM batteries. The modern batteries are great and have real advantages over lead acid, being more efficient and capable of being stored in cupboards, even on their sides and they are lighter. But they are very expensive and often need special chargers. In our van we have 2 lead acid leisure batteries, rated at 75AH each. The AH figure stands for Ampere Hour, which is the maximum current the battery can deliver for an hour continuously. A 50AH battery can deliver 50A for one hour or 5A for 10 hours. Connecting two in parallel doubles the capacity, so 2x50AH has a total of 100A available for a hour etc. Just remember to allow the batteries to vent to outside via a vented compartment or a simple tube from the battery vented through a suitable hole to outside.
Finally we have the solar panel. Panels are rated with a Voltage and a maximum Wattage output (remember the formula). Make sure you buy 12v panels (which can in practise deliver up to 18v, but that doesn’t matter as the solar regulator will sort this). Buy the biggest Wattage you can fit on the roof as the Wattage figure is a notional instantaneous output, based on perfect conditions such as being clean, in full sun, at the optimum angle etc. They never deliver that figure in practise, so buying a bigger panel gives you the best chance of recharging the batteries after you’ve been using them. We will look at the different types in Part 2.
Our setup is a 120w rigid panel feeding two 75AH batteries, giving a total of 150AH which has been more than enough for at least a couple of days, even in Norway in winter where we used the heater and cooker daily. Our 120w panel can notionally deliver 10A for recharging the batteries, which is enough although we usually see around 5A.
Remember the panel doesn’t give power at night or in shadow, but will give some power on most days provided it sees daylight. Bright sunshine and tilting the panel towards the sun will see the best results.
In part 2 we will cover the selection and installation of the equipment.
When working with electricity, disconnect all the batteries.
If in doubt, consult an electrician
By thelittleredbus.
The Little Red Bus 