This article has been modified from its original appearance in Living in a Small RV – How we camp free and work remotely in our off-grid RV.
There are household items that need to be charged; there’s just no way around that. We have laptops, cell phones, tablets, and small battery packs. Electrical power is just one of the necessities, especially when you’re working remotely. But how do you get power when you’re not at a campground with an easy power connection? It boils down to your budget. There are some cheap options, but they aren’t convenient and they have their limitations. The goal here is to live in freedom and comfort. The more points of friction that you can remove from your life on the road, the better, and the longer it is that you’re likely to stick with the lifestyle. We’ll cover the smallest and least expensive option, eventually making our way up to the most expensive (and most convenient) option.
Inverters are devices that transform energy from batteries into electricity that’s usable for electronic devices. These come in all different sizes, but in their simplest form they’re small enough to plug into your car’s cigarette lighter. Some more recently manufactured vehicles have built-in USB ports, and while these work for things that can be charged via USB, a laptop is a different story. Devices with a larger power draw require an actual plug, which is built right into small inverters.
Inverters are measured in “watts”, and you should purchase an inverter with a large enough wattage to cover your devices’ power consumption. For example, Nick’s laptop requires a flow of 160 watts to charge. So the plug-in inverter should have a wattage of at least 160. You can find these on Amazon or in auto parts stores such as AutoZone.
These inverters are cheap, but they aren’t super convenient. They also aren’t large enough to power things like coffee pots and microwaves, and they drain your vehicle batteries, so if you’re not careful you could leave yourself strand- ed! Nonetheless, inverters serve as a great option if you’re just looking to get your feet wet with boondocking. We have a 300-watt inverter that stays in our truck permanently, powering Kindle readers, iPhones, and (when necessary) Nick’s laptop.
The next logical step up from an inverter is a generator. It’s a pretty reliable source of power, as long as you keep it properly maintained. Most RVs come equipped with a generator that’s used to recharge the house batteries, power the A/C, and provide current to the wall outlets. If your rig lacks a generator, you might be tempted to use a normal generator like you might find at a construction site or powering a house during a storm outage. Those are not the kind of generator you’re looking for.
Those don’t belong in a boondocking environment. They are very loud, are not fuel-efficient, and the electricity they provide isn’t as “clean” as the electricity that comes from an inverter-style generator.
Instead, check out the 2,200-watt Inverter-Generator from Honda. This is a special type that is extremely quiet and capable of daisy-chaining with other units to power your whole rig. They’re also really light-weight and portable.
But a generator like this still requires fuel and makes noise. You might be different but we like to hear nature, not the hum of a generator. We full-timers need something that just works all the time.
The benefits offered by solar just can’t be beat. There’s no generator noise, no additional fuel cost, no moving parts, and no significant maintenance. Additionally, the electricity that comes from a solar system is arguably cleaner than that of a generator, or even that of the modern-day electrical grid.
The solar array on top of our rig powers everything except the A/C. We are “weather chasers” anyway — we chase the cooler climates and try to avoid hot weather. And really, unless you are hanging out in the Deep South, even temperatures in the 80s aren’t bad if you have fans and shade.
We use a toaster for breakfast, a normal coffee pot (twice a day), and we reheat food with a microwave. All of the plugs in our RV work all the time, and for the most part we just don’t ever think about the electrical power we’re consuming.
But this convenience comes at a cost, and it’s not so much the actual solar panels (which are relatively inexpensive); the cost comes in the components that are needed to run the system: the batteries and the inverter.
How Solar Systems Work
Before we go on, here’s a quick primer on how solar systems work. It’s important to at least understand the fundamentals before you consider having a system installed. Warning: technical jargon incoming!
Sun rays first hit an array of flat “photovoltaic” cells which are mounted on flat solar panels. The rays (photons) excite electrons in the silicon cells, turn- ing that into energy. This energy is carried through to a solar charge controller which regulates the voltage of the energy entering the system. The charge controller relays that energy into batteries, which can be configured in a couple of different ways. The batteries’ output is measured in amp hours. For reference, the rate of flow that a 1-amp light bulb draws for one hour is around 1 amp of current. That’s it for the energy-gathering part of the system. The second part of the system is energy storage. In order to use the energy, stored in the battery as DC (‘Direct Current’), the current must be converted to AC (‘Alternating Current’). This conversion requires an inverter unit.
An inverter pulls energy (DC) from the batteries and transforms it into energy that can be used by anything we plug into the wall (AC). Converter units are sized in watts, similar to the smaller plug-in inverters covered earlier. The inverter is the most expensive part of the system ($2k). We have a 3000-watt unit which allows us to simultaneously run the toaster, coffee pot, and microwave without fear of overloading the system.
This kind of system is expensive up-front, but you’ll recoup the cost by boondocking for free every night!
A Note on Battery Voltage
Concerning voltage: the resting voltage for a fully charged 12-volt battery is 12.6 volts. But, you have to charge batteries to at least 14.2 volts, and they have to be held at that charge level for at least two hours to be considered “full.” If you can imagine the battery bank as a bicycle tire, the solar charge controller is the pump and the voltage is the air. It’s easy to pump in air (amperes) at the beginning, but it gets progressively harder as you reach the pressure capacity (maximum voltage).
This is how batteries respond to being charged. It takes a lot of amps being pushed into batteries to get a battery to 14.2 volts. In a typical solar system, it takes at least as many watts in solar as you have in amp-hours of battery capacity. In other words, if you have 600 watts of solar power, you should have around 600 amp-hours of battery storage. (We would personally want more solar panel than battery, because the winter sun is a lot lower in the sky, which equates to fewer peak hours for solar.)
How big of a system do I need?
The answer to this question depends on a lot of different factors. How many people are in the rig? How much roof space is on the rig? How many modern-day conveniences do you want? Do you want to be able to run a toaster or a microwave? Do you want to be able to run a coffee pot, or are you OK with pour-over coffee as a sacrifice for power efficiency?
There are a lot of solar system calculators on the web, but most of them are offered by companies that will also try to sell you whatever their calculator recommends. To avoid this, we can offer you a few baseline recommendations.
We’re a family of four. We’ve got 3 laptops, 3 tablets, 2 kindles, and 2 iPhones. We can use our toaster and coffee pot at the same time. We also have a micro- wave. We can plug in and run anything at any time of day.
We have a 750-watt solar array made up of three panels on the roof of our RV, and one of the panels is designed to detach from the roof to be deployed on the ground. We use this detachable panel in the winter to supplement the so- lar array when the sun is lower in the sky.
Total cost of system: $5,000
Our solar system stats:
Not everyone can afford this system, and for the longest time we couldn’t either. In fact, we spent our first three months boondocking with a generator, two old lead-acid house batteries, and solar-powered lanterns! During that time we did a lot of research and we found some inexpensive solutions, like a solar system in a box. These all-in-one systems are fairly inexpensive, containing the battery, controller, and inverter. GoalZero makes a great system that’s relatively inexpensive, depending on the scale you need.
Ultimately, we decided to just pay the money for the system we have listed above, and we’ve long since recouped those costs by boondocking. Now, the investment pays us dividends.
On Inverter Sizing
The 3000-watt inverter is admittedly overkill. Nick originally spec’d this out to run the entire coach, including air conditioning. But after people who work on these systems for a living convinced us otherwise, we scrapped that plan. Having an inverter of this size allows us to run multiple appliances at once, including the coffee pot (1200 watts) and the microwave (1000 watts).
If you don’t need to run multiple appliances at once, then a 2000-watt inverter will be more than enough. With 2000 watts, you can run the coffee pot and still have about 800 watts of headroom.
Consumers can choose from three different types of batteries for mobile solar systems. Lead-acid batteries (used in consumer vehicles and RVs) have been around for over a century. But, they’re heavy, they get corrosive, they vent gas, and they often need maintenance (adding water).
Additionally, a lead-acid battery shouldn’t be allowed to discharge past 50% capacity. Allowing the battery to discharge below this point can damage the battery long-term, resulting in a far lower overall lifespan.
Next up, we have AGM (Absorbent Glass Mat) batteries, the type of batteries we use. These do not vent gas, do not need to be maintained, and can be stored in any orientation. Like lead-acid, AGM batteries should not be discharged past 50%. The low discharge threshold essentially means that if we have 600 amp hours of storage in our battery bank, we really only have 300 amp hours to work with. Keep that limitation in mind if you decide to go the AGM route. Like lead-acid batteries, AGM batteries are heavy. We have six 6V AGM batteries weighing in at 70 lbs. each!
At the top of the list you have Lithium Ion or Li-ion batteries. These batteries are lightweight (30 lbs. where AGM would be 70 lbs.), and can be discharged down to 0% capacity. They also recharge faster than lead-acid and AGM bat- teries. The advantages of Li-ion batteries come at a cost: $1,000 for a single 100-amp hour battery. To put this into perspective, a 100-amp hour AGM battery may only cost $100 — a tenth of the price of Li-ion. But if you’re in it for the long haul, cutting battery weight in half, reducing charge time, and not having to worry about discharge threshold might just be worth the cost!
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