After adding a fridge, a winch, fancy GPS navigation systems, an air compressor, outlets to charge up the Instagram-machines, and enough lights to convincingly turn night into day, you might find yourself wanting for electricity. Especially if you’re spending extended periods of time using power around camp, your alternator might not be run enough to your battery (or even batteries) topped up.
Seeing as how the sun is kind enough to bathe us in what is essentially free energy every day (weather permitting), adding some solar panels into the mix starts to make a lot of sense. Of course it’s not quite as easy as slapping a couple panels on your rig and running some wires to your battery, there are a few more considerations to be made. However, the technology has come far enough along that it’s pretty accessible stuff for most people.
Figuring Out Your Power Needs
The first step here is to get an idea of how much power you’ll be using and for what period of time. Most likely if you’re looking into solar solutions, you either have an auxiliary battery setup or are looking into getting one (highly recommended). That could mean a second lead acid or AGM battery, or, to save weight and space, utilize lithium-ion cells instead. Especially if you’re running a fridge, this is a nigh-on essential addition.
While a common lead acid battery offers great dollar-for-watt value, for off-road use we usually like to recommend a sealed AGM battery, if not lithium-ion. AGM batteries can’t be spilled, are less maintenance intensive, and tend to last longer than gel-cell batteries. Lithium-ion batteries are more expensive, but saving the weight and space can make the cost worth it alone. They also tend to last the longest and offer the most consistent charging over the lifespan of the battery.
Note: One side consideration that a solar solution brings up is whether to run your auxiliary battery and solar panels with your main battery that powers your ignition and is charged by the alternator, or to keep the circuits separate. There are pros and cons to each, so this largely depends on your usage as well as how sophisticated your charge controller is. Some controllers will selectively limit or restrict power depending on how much charge you have left. This goes for some more advanced fridges as well. The point is you don’t want to be left stranded with an expensive and fancy looking array of dead batteries.
If you’re not sure exactly how much your power draw typically is, a safe baseline for a setup would be 150w of total power from the panels. Running a pair of 75w panels is a popular solution, as they are readily available at a number of price points and are manageable enough in size to be able to fit most setups.
Those with less power-hungry setups can get away with 100w of solar power pretty well, that would be enough to provide roughly 30 amp-hours worth of electricity on most days (again, weather permitting), which should be enough to keep a fridge running at least.
Fixed or Portable Panels
Then there is the question of whether to go with fixed or portable solar panels -- or some combination of both. Which direction you go here depends largely on your vehicle, but also on the surroundings you tend to find yourself in when out and about.
Practically speaking, you’d be forgiven for not wanting to drill holes in your roof, of course. There are plenty of options on the market for mounting solar panels to roof racks, but that might restrict otherwise useable space. If you have a hard-panel rooftop tent, that’s a great place to mount the panels.
What you have to ask yourself now seems obvious on the face of it, but many people overlook a very important factor: Where are you going to parking/setting up camp? If you usually find yourself camping under tree cover or in a shady canyon (which is a likely scenario in warmer weather), then your solar panels aren’t going to do you much good when camped
Portable panels can be set up out away from your vehicle to a sunny spot, and can even be aimed towards the sun for added efficiency. The other advantage here is that you don’t need to make the commitment of a permanent mount location that might take up space where other gear can go. The downside is that you likely won’t have a great way to deploy the panels while on the move, hence why many overlanders invest in both solutions for the best coverage.
Note for the overland fridge owners out there: It’s important to take downtime between trips into consideration! Are you going to leave the fridge in your rig? Pull it out and use it as a garage fridge for a bit? It’s a good idea to keep the fridge powered even when not in use, or if you do take it offline, make sure to thoroughly clean it out first. You’ll thank us later!
Let’s Talk Charge Controllers
Unfortunately you can’t really just shove the wires from the panels up against the battery terminals and hope for the best, you need a charge controller (sometimes referred to as a regulator) to manage and convert the power coming in to charge the battery safely and efficiently without overcharging.
You have two options here: Pulse Width Modulation (PWM) or Maximum Power Point Tracking (MPPT)
PWM controllers tend to be less expensive and will get the job done, but MPPT controllers offer around 20%-30% better efficiency and more versatility for different panel and battery setups. If you can swing it, we recommend a solid MPPT controller, as these will offer different modes to optimize charging for lead acid, AGM, or lithium battery setups. They also tend to offer more efficient modes for adjusting power distribution based on current charge, power consumption, and power inverter usage.
The last consideration here is to make sure you are using the proper gauge wire for your setup. With a 100w-150w system, you should be safe with 12 gauge wiring from the panel -- this will be plenty enough to handle the power being transferred while being easy to work with a route than 10ga wire. It’s also important to remember to always make sure that gear being run off of your auxiliary setup uses the proper size fuses for the power being used.
Have you taken the plunge on solar yet? Have any questions on your specific setup or needs? Have any tips we missed? Drop a comment below!