It's a familiar story: You fully charged the Airstream's batteries before putting it into storage (or into your garage), and put the Battery Disconnect switch in the "STORE" position – as it should be. A few weeks later, you went back to the Airstream to find the batteries completely flat.
I hear versions of this all the time. And now that we store our Airstream off-site in between trips, I'd been running into the same problem myself.
Every Airstreamer should be concerned about the batteries going fully dead. After it happens a few times you'll find the batteries will stop taking a charge entirely. When that happens, the problem becomes expensive–you'll have to buy another set of batteries.
The most common culprit
Why do bad batteries happen to good Airstream owners?
Because an Airstream is never truly "turned off," there's always some electronic device silently sucking power out of the batteries. If left unchecked, that power drain will eventually tap out the batteries completely.
People call this "parasitic drain" or "vampire drain" but in the industry it's more commonly referred to as "standby." Whatever you call it, what's important to understand is that a tiny trickle of electronic neediness will add up over time.
My 2020 model year Airstream has lots of neat electronic gadgets that have little control boards. Some of those boards sip power even when the device is turned "off." These can include the stereo, refrigerator, and water heater. Other devices that need a tiny amount of power constantly include the TV antenna booster, a TST repeater/booster, and the propane leak detector.
All of this power sipping can add up to your batteries being drained completely when the Airstream sits in storage, unplugged. Even when you flip the Battery Disconnect to the "STORE" position, some items (primarily the propane leak detector) never turn off.
How long will the batteries last in storage?
When a device's power requirement (or "draw") is very small, we don't worry about it during travel. I'm talking about draw of less than 0.1 amp. In daily camping life, these things are not significant.
But when you've parked the Airstream in storage, this draw adds up over time.
How much? Let's do the math.
My Airstream's original lead-acid batteries held about 62 usable Amp-hours (Ah) of power. This was printed on a label atop the batteries.
In my Airstream, all the parasitic draws add up to about 11 watts, or 0.81 amps. (I know this because I installed an amp-hour meter.)
Take 62 and divide by 0.81 and you get the number of hours those batteries will last before they're discharged too much. In this case it's 76.5 hours, or just over 3 days.
"Whaaa? Just sitting there doing nothing, my Airstream batteries will only last for 3 days?"
Yes, although the amount of time will vary depending on the capacity of the batteries you have installed. After that, the batteries will be drained too much, which can shorten their lifespan considerably. Repeat this a few times and you'll need to replace them.
"But isn't the reason for the Battery Disconnect switch to turn off the power?"
You'd think so. But even when the switch is in the "STORE" position, it doesn't quite turn off every single thing.
Anything directly connected to the battery, such as a TST repeater/booster and the propane leak detector, will still draw some power. On my Airstream, that's about 3 watts or 0.19 Ah.
Do the math again, and we find that even with the Battery Disconnect switch the battery bank will last just about 13-14 days. That may not help. If your Airstream is unplugged in storage for a few weeks at a time you're still going to come back to dead batteries.
How to avoid the problem
What's an Airstreamer to do? You've got a few options:
- Leave the Airstream plugged in, if you can. Airstreams in model years 2018 and later generally have multi-stage chargers that are OK to leave plugged in all the time. This is not a great strategy for older Airstreams with single-stage chargers, as there's a risk of overcharging the battery in the long run.
- Install rooftop solar of at least 90 watts, to keep the batteries charged. Of course, this only works if your Airstream is out in the sun and it's not too gloomy during the winter.
- Disconnect the batteries during storage. This is my preferred option. You just disconnect the negative cables from the battery. If you don't like messing with wrenches and power cables, have somebody install a nice neat "quick disconnect" switch on the negative terminal and connect all the negative cables to it.
Even with the batteries disconnected you may have to charge up the batteries during long periods of storage. Lead-acid batteries (which includes AGM batteries) will "self-discharge." The rate varies, but figure about 5% of the total capacity will be lost each week, which means conservatively you should plan to top up the batteries every couple of months at least.
If you have lithium batteries, self-discharge isn't a concern if you've disconnected them. The lithium battery chemistry used in RVs only self-discharges about 2-3% per year.
Follow these tips and your batteries should last for years. The golden rule with batteries is: Always Keep Them Charged.
Photo credit for featured image: Agent J on Unsplash