The world of solar has created so much freedom when it comes to camping in comfort. A top end solar and battery system will keep your appliances (even 240V ones!) running endlessly, so you never have to run a generator, or plug into 240V power again. That sort of freedom is priceless; days on end camping along the Ningaloo Reef, or somewhere else super special.
Unfortunately, like a lot of camping and 4WDing topics, solar is one of those things that regularly is made far more complicated than it needs to be. In this post, we cover absolutely everything you need to know about solar panels, how to run them, what to buy, how many you need and the list goes on and on.
Solar isn’t the only thing you need
To start with, know that solar panels work together with your 12V batteries to provide the power you need. A big set of batteries on their own is no good, and likewise a number of panels feeding a tiny battery wont be any good either.
You also need a good quality solar regulator that can take the suns energy from the panels, and turn it into usable, battery charging power. A heap of panels connected to a poor quality solar regulator will not do you any favours.
Lastly, if you want to run 240V power, you need a suitable inverter. This is often 50 – 100% larger than the running current draw of your appliance. If you want to run a 1200W induction cook top, you are probably going to need a 2 – 2.5kw inverter.
Everyone’s systems and needs are different
If you have a 4WD that just needs to run a few LED lights and a fridge, your needs are vastly different to someone with a someone running caravan air conditioning (yes, its possible!). Of course, the principles are still the same, and you need to go through the same process to identify what you need to buy, but its all about setting a system up that is going to do what you need it to.
Work out your power consumption
The first step to buying solar panels for your camping arrangement is to work out your power consumption. You can either measure and calculate this, or take rough measurements online, or just guess it all together (the least preferable method!).
Watt metres are a fantastic piece of equipment, which you can plug into fridges and they will tell you exactly what sort of current draw you are getting. They cost very little, and make life awfully simple.
Before we go any further, this can seem awfully complicated, but it isn’t. Power consumption is considered in terms of amp hours (despite everyone saying amps). Sometimes figures are given in wattage, but it can easily be converted. 12.5 Watt hours is generally around 1 amp hour, but it does depend on your battery voltage.
Fridges tend to pull around 1.5 – 8 amp hours (19 – 100 watt hours) when running, LED lights use very little power, water pumps around 4 amp hours and the list goes on. When you know what your current draw is, you can work out the right battery size and then solar.
When you read the specifications for appliances, make sure you look at the actual running power consumption. 12V fridges for example have a habit of saying the power consumption is 3 amp hours, but what they actually mean is that this is the average consumption per hour over 24 hours.
When running, it might actually pull 5 amp hours, but it cycles on and off, reducing the average hourly use down to 3 amp hours.
Battery capacity should be 2 – 3 days worth of total consumption
Running normal deep cycle batteries down below 50% regularly will dramatically reduce their life span. This means for every 100 amp hours of battery capacity, you should base it off only having 50 amp hours.
If you use lithium batteries, the most common figure used is 80%, so you can use 80 amp hours of a 100 amp hour battery. Once you know your total consumption per day, your battery system should be able to run for 2 – 3 days without any charge going into it at all, and you’ll have plenty of reserve should things go wrong.
Please note the 2 – 3 days is a figure you’ll have to choose, based on how you travel. If you move every single day, you can get away with enough solar for just one or two days, but its not uncommon to have a couple of days of solar, and some people aim for 5 – 6 days worth of battery capacity, for when the solar is simply doing nothing.
Of course, this isn’t always practical, and like us, we are happy to go for a drive if we get numerous days of overcast weather and to keep the solar and battery system smaller and lighter.
Solar should replenish your daily consumption within 6 hours of sunlight each day
Solar panels work most efficiently when they are cold, and angled directly at the sun. Where you are in Australia will result in significant differences in performance of solar panels, and you should base your calculations off only getting around 5 – 6 hours of good sunlight each day.
Have a think about how the length of the days will affect your travels too; on a long, warm summers day you’ll get far more sun than you would in winter time in many parts of the country.
Ideally, you want your system to be fully charged as the sun goes down each day, with room to spare in case its cloudy for a few days in a row, or you have your panels in the shade for some time. Essentially this means that your consumption over 24 hours needs to be able to be recharged within 5 hours.
If you use 120 amp hours in a day, you’d need to be putting back around 24 amp hours into the batteries when the sun is out to be full again at the end of the day, and that’s a fair bit of power.
The weather is a huge factor
A lot of people overlook the weather, and get into trouble. We’ve covered overcast days already, which is a huge factor in designing your 12V solar and battery system, but the temperature is another thing that needs consideration.
When its hot, your solar panels will not work as efficiently, and this is particularly the case when its 35 degrees and above. Often the days are longer which can marginally make up for it, but your solar panel generation will decrease.
Beyond that, the hotter it is, the more power your fridges and freezers will require, which is where a huge chunk of extra power goes to. Between a 20 degree day down south and a 35 degree up north the power consumption can be 50% increased, especially if you house your fridge or freezer in something that gets warm.
Our Reconn R2 fridge slide goes into a black box essentially, and it gets quite warm. We make a point of keeping it open when we are at camp, so there’s more air flow.
If its really warm (and your setup allows for it) you might want to run an air conditioner for a few hours, which is going to work your battery system seriously hard.
Portable vs fixed solar panels
Inevitably, you’ll need to decide what type of solar panels to get, and where you are going to mount or store them. You can either go for fixed solar panels, which are bolted to your 4WD, camper trailer or caravan and never move, or you can go for portable ones, which you pull out and plug in when you get to camp.
There’s a huge number of pro’s and con’s to each setup, and in many cases its a good idea to have both options should you need it. However, we’ve already written a comprehensive post on this, which you can read here; Fixed vs portable solar panels.
Solar blankets vs solid panels
If you do go down the portable panel path, you then have to decide whether to get a folding (or single piece) solar panel, or a solar blanket. Again, there are pro’s and con’s to both, and they both do the same job. You can read our comprehensive post about this here – Solar panels vs solar blankets.
Picking a regulator
You cannot connect a solar panel directly to your battery, or you’ll end up with some nasty damage. You need a regulator between the two, which reduces the wattage down to a suitable level to charge the battery. Most 12V panels come in at about 18V, and if you feed that into your battery you will cook it in a matter of minutes.
Regulators convert the power, and reduce the charge rate as the battery gets fuller, until its in float mode, and essentially full. A lot of people are using dedicated DCDC battery chargers that have inbuilt solar regulators in them, or you can go for a quality MPPT unit like a Victron 100/30, or on the cheapest end of the scale a basic PWM regulator that you can buy for under $30.
If you are going to buy any good quality parts in your solar setup, make it the regulator as its the brains and brawn of the operation. A good panel and battery will suffer badly with a poor quality regulator.
We are really happy with our Victron MPPT and Enerdrive DCDC, and would have no issues recommending them. They are two of the most reputable brands on the market, but do your research and don’t just rely on my opinions!
A practical battery and solar example
It’s always easier to explain something when you use a physical example, so today we are going to use Joe’s 4WD, who wants to run a 85L fridge freezer, lights and a small inverter for charging his 18V Makita tool batteries, laptop and camera batteries.
There’s actually a number of power consumption calculators online, which allow you to enter different appliances in, and play with the results.
Anyway, back to Joe’s 4WD, who wants to be able to pull up anywhere in Australia and kick back for a a couple of days at a time without moving his vehicle. This means he needs the solar to easily keep up with the demand without using the alternator on his vehicle to charge any batteries.
Joe looks up the specifications for his fridge/freezer, and it averages 2 amp hours. A couple of LED’s for a few hours a day is another 5 amp hour, and his inverter charging small appliances is another 15 amp hour for the day.
The total consumption over 24 hours is (1.5 x 24) + 5 + 15, giving a total of 56 amps consumed. This is a fairly typical example of a 4WD owner who travels, excluding the needs of a trailer if its being towed.
From there, Joe, can size his battery capacity by multiplying 56 x 2 days, which results in 112 amp hours of usable capacity needed. If he goes down the path of normal lead acid batteries, he’ll need double that in capacity – around 240 amp hours of lead acid batteries to give him two full days of consumption without any charge going in.
If he goes down the lithium path, he’ll need around 140 amp hours of batteries to only use 80%.
Then, to work out the solar needs, he has to replace one days consumption in 5 hours, which means 56/5, or 11 amp hours going into the battery, for 5 hours.
11 amps is around 140W, which is the panel size he’d need to be looking at. Now, a lot of panels do not put out their rated specifications, and you’ll find some 200W panels that won’t even do 140W. Joe decides to mount two 150W panels on the roof racks of his 4WD, so he never has to move panels around.
If its cloudy and he generates no power for two days, he’ll have to go for a drive to top the car up, but as long as he gets some sun it will run almost indefinitely.
The subject of solar panels for camping gets made far more technical and confusing than it really needs to be. It’s as simple of working out your consumption and fitting a battery and solar system that will handle it easily. With solar, you are better off having more than less to accommodate for poor solar days, but its a super simple, and easy way to run your appliances off grid.
What have I missed? Let me know below.
What solar and battery system do you run?