If you’re putting your RV away for the winter—or already have—make sure your house batteries are stored properly. Proper storage ensures that batteries won’t freeze and that they’ll be ready to take a full charge come spring to serve you for another camping season. With lead acid and AGM batteries, you don’t want freezing to occur because battery cases can expand and crack if frozen, ruining the battery. Leaking battery acid can damage concrete underneath and other materials nearby. Don’t leave your house batteries in place, exposed to freezing temperatures and unattended all winter. That’s a sure recipe for battery failure. Store batteries in a cool, dry place—in freezing climes, a basement is great. With acid-containing batteries, your storage spot should have an available electrical outlet for a charger. Traditional Lead Acid Batteries Befitting batteries with the oldest technology, lead acid batteries also require the most work for safe storage. But, hey, they’re cheap and if well maintained, reliable. First, clean dirt and buildup from the terminals and battery casing. The buildup is highly corrosive, so wear gloves and eye protection. Ignoring the buildup can accelerate discharge. Pull off each cap and check the water level. If tops of the metal plates are exposed, fill the battery with distilled water until the metal is submerged. (This is why they are sometimes called “wet batteries.”) Distilled water prevents mineral buildup. Use a multimeter to check the charge level. It should be close to 100 percent before storage. If it’s low, apply a charge until the battery comes up to 90 percent. This may take eight or more hours. Then apply a 2 amp charge to top it off. Place the battery on cardboard or wood. Concrete won’t drain modern batteries, but it is cold, and cold is a lead acid battery’s enemy during storage. Here’s where the high-maintenance part comes in: A lead acid battery loses 5 percent or more of its power per week, so check your battery every month. It should not fall below 50 percent. Allowing the charge to fall below 50 percent can lead to sulfate buildup inside the case, and to freezing and cracking. If that happens, you’ll need to buy a replacement. One way to slow power dissipation is by attaching a battery minder, also called a battery tender or maintenance charger. It’s a small charger—or an adjustable charger—that delivers a 2 amp charge. A battery that’s close to 50 percent discharged can be hooked to a higher-amp charger—say, 10 amps—for a few hours to restore full charge. A battery maintenance charge can then be applied. Some chargers will switch automatically from full charge to a maintenance charge. AGM Batteries An Absorbent Glass Mat battery is a more advanced lead acid battery, so preparation for storage is similar—but simpler. Clean off residue and mineral buildup as you would on a traditional lead acid battery. AGM batteries are sealed, so there’s no need to check the water level. They can be mounted or stored in any position. Use a multimeter to determine the charge level. Bring it up to full charge before storing. Power loss on an AGM battery is slower than with a wet battery, but so is recharging. AGM batteries sometimes can take more than a day to recharge. Read the manual for your battery. Check every four or six weeks to see that the power level has not fallen below 50 percent. Apply a 2-amp battery maintenance charge to keep the power reserve from falling below 50 percent. Lithium Since a Lithium Iron Phosphate deep-cycle battery costs more than double what an AGM battery does, you don’t want to store one incorrectly. Storage is the easiest of all RV battery types. Lithium batteries don’t require maintenance—they’re sealed. There’s no checking fluid level. You don’t have to worry about sulfation inside these premium batteries. And you can store them in any position. A proper charge level for a lithium battery before storage is 40 percent—much lower than for a lead acid battery. A higher charge could result in damage to the lithium during storage. If it’s too high, disconnect the battery from charging equipment, then attach a light or two to bring the charge down. Like other batteries, they can be kept in a cool, dry place. Unlike the others, they can remain in your RV and won’t freeze. They do not require monitoring or a maintenance charge. Return them to your RV after storage and recharge them then, or recharge them in the spring when temperatures rise and remain above freezing. Lithium batteries can be discharged at temperatures as low as 4 degrees below zero, but never recharge lithium batteries during freezing temperatures. Lithium Iron Phosphate batteries lose a much smaller amount of stored energy than lead acid batteries do, so storing one at 40 percent should keep it safe all winter without a maintenance charge. If You Did It Wrong If you stored your batteries improperly or, worse, left acid batteries unattended in or outside your RV, go back and do it the safe way. If not, you’ll have to apply a recharge intermittently to prevent freezing and self-destruction. It’s much easier to remove house batteries and store them properly, intermittently monitoring their power level.