Following up on our previous post about Conserving Power While Boondocking — another major way to extend your power supply is to understand where the power goes.
The built-in battery monitor won’t help with that. You will need to install an accurate amp-hour or watt-hour meter that measures the amount of power being consumed in real time.
A good amp-hour meter with a digital readout (made by Xantrex, Bogart Engineering, and other companies) requires some installation and money, but for those who frequently camp without hookups it’s well worth the investment.
With a real monitor you can see what each light and appliance is consuming, and identify the big users so that you can avoid them or upgrade them. Right off the bat you’ll see that your RV furnace is a huge consumer of electrical power, so you might want to consider an extra blanket on the bed or even a catalytic heater (which uses no electricity). Incandescent lights (on older Airstreams) are also big consumers, so if you don’t have LED you should seriously consider upgrading the most-used interior bulbs or entire fixtures.
Studying power requires you to understand just a little bit about how electrical power is measured. The amp-hour meter will measure the 12 volt DC power coming off the batteries (or going back in when charging) using amps. Constantly drawing one amp from the batteries for an hour will total one “amp-hour.” The meter will keep track of amps going in and out at any given time, and also keep a total of the amp-hours used since the battery was last fully charged.
(If you want to think of the power in terms of watts instead, just multiple the amps by 12. But for the purposes of this discussion we’ll stick with amps.)
A typical Airstream trailer comes with a pair of Group 27 batteries (that’s a physical size, not power capacity). They might each be rated at 85 amp-hours capacity for a total of 170 amp-hours. But because you should only discharge them to half of their total capacity (for longest life), your net capacity from two batteries is really just 85 amp-hours.
The furnace pulls about 7-10 amps while running, depending on model, which adds up to a lot of power when you consider how long it runs on a cold night. It’s one of the biggest DC power consumers in the trailer. That’s why setting the thermostat lower on a cold night will help a lot.
Just two nights of furnace can easily drain the usable capacity of the standard pair of batteries in an Airstream trailer. By monitoring the electrical “cost” of running the furnace with the amp-hour meter, you’ll understand what’s happening before the power goes completely flat.
Why do trailer batteries go flat even when you’re not using anything? An amp-hour meter can help you understand “parasitic” loads on the batteries. Several devices draw small amounts of power even when they are not in active use, and that’s what we call a parasitic load. This includes the circuit board in the refrigerator, the propane leak detector, the stereo, the circuit board in the water heater, etc. All of those little parasites add up, and it’s not uncommon for them to total an amp or so of constant draw.
A one-amp parasitic draw means all of your useful power will be gone in about 85 hours—just three and a half days—even if you aren’t using anything else in the trailer at all! This is why Airstream provides a STORE/USE switch to cut power to most systems when the trailer isn’t being actively used.
With the amp-hour meter you’ll be able to see the exact parasitic draw and get an idea of how it combines with your routine power usage while you’re camping. Soon you’ll understand why there are so many posts in online forums from new owners asking why their battery was dead after just one night of running the furnace.
If you frequently run out of power when boondocking and you don’t want to spend the big bucks to get a generator or solar panels, the easiest and cheapest option is simply add more battery capacity. There are several ways to do this, and the best solution depends on the layout of your Airstream. Usually people find a spot toward the front of the trailer (such as under a couch or in an external storage compartment) to install a bigger battery bank.
At the same time it’s an opportunity to upgrade to Absorbed Glass Mat batteries, which last longer and are safer than ordinary “wet cell” batteries. Going back to the electric car analogy, more battery power is like going from a Nissan Leaf (with an 80 mile range) to a Tesla Model S (230 mile range). Suddenly your “range anxiety” is greatly reduced and you can actually go places.
The larger battery option is less costly than a “quiet” generator or solar setup, with the advantage of always working regardless of sunshine or fuel supply. For most people, more battery capacity and better conservation are enough to get a few extra days of boondocking.
Knowledge is power, and in this case more power is mostly a matter of more knowledge. You’ve got options to explore. If you find yourself addicted to the off-the-grid lifestyle, congratulations! It means you’re enjoying your Airstream, and that’s a good thing.