It’s that time again, crops are coming out of the fields, leaves are turning, and cold weather is just around the corner. We may be able to get a few more weekends of camping in, however, it is time to start thinking about storing our RV for the winter.
Most RVers know what to do about winterizing the freshwater system with either antifreeze or blowing out the lines with air however, few take the time to identify the type of house battery they have and how to properly store it. Should you leave the unit plugged in to keep the battery charged, remove the battery or batteries and keep them in a garage, or just let them sit?
Types Of Deep Cycle Batteries
The batteries used to power your 12-volt components in an RV commonly referred to as “House Batteries” are deep cycle which means they are designed to be drawn down to a certain percent of power or amp hours and recharged several times. This is what a “cycle” is referring to. They are designed to provide prolonged 12-volt power over time vs a chassis or engine battery that is rated in Cold Cranking Amps (CCA) and designed to provide high power to turn an engine over for 30 seconds.
There are three types of deep cycle batteries used in RVs, Flooded Lead Acid (FLA), Absorbed Glass Mat (AGM), and the newer Lithium Iron Phosphate (LiFeP04). Each version has a different charge profile and also a different recommendation for storage.
Flooded Lead Acid (FLA)
These batteries have been used for years and are still the “standard” battery due to availability and cost. If you are not boondocking, or dry camping much and don’t need high amp-hour capacity, the FLA battery is perfect, it just needs a little more maintenance and TLC when it comes to charging and storage. FLA batteries have lead plates inside that are covered in acid and are prone to sulfation. As the power is drawn down, Sulphur coats the plates and requires a multi-stage charge which starts with a bulk stage that is a high voltage charge and breaks up the sulfation. Most RV converters/chargers do not have this, rather an initial charge of 13.6-volts and a maintenance charge of 13.2-volts. This will not break up the sulfation and the battery will lose storage capacity. It will also “gas” the acid and you will need to check the fluid level at least once a month.
FLA batteries will naturally drain power if not connected to a charger and even faster if left connected in a rig that has components that will run even with the battery disconnect switch in the off position which should mean everything is disconnected. However, the LP leak detector typically bypasses the disconnect switch and will drain a battery in less than 2 weeks. A drained battery will sulfate faster and in cold weather, a low battery can freeze and ruin the battery. FLA batteries need to have the fluid level checked more often as well.
If you have access to 120-volt power, I would recommend not plugging in the shoreline cord, rather get a portable 120-volt battery maintainer that has desulfation such as the Battery Minder. Plug that into the storage facility outlet and connect it to the battery. You can find the Battery Minder at Northern Tool. The smaller unit will be sufficient for two house batteries.
If you do not have access to 120-volt power at the storage facility you can use a small solar panel and a charger/desulfation product like the Battery Minder, or remove the batteries and hook them up to one in a garage. Another option is to go to the storage facility and start the unit every 30 days and let it run with a desulfation product for an hour or more.
Absorbed Glass Mat (AGM)
AGM batteries also have lead plates covered with acid like the FLA models but are sealed and have a fiberglass material between the plates and are less susceptible to sulfation. However, a misconception is that AGM batteries will not sulfate however they can still be affected without the proper charge and storage.
Most AGM batteries require an initial charge of 14.4 – 15 -volts and then a float or maintenance charge of 13.5 – 13.8 – Volts. So the typical RV converter/charger will not be effective in maintaining an AGM battery and especially not during storage. However, if your rig has a programmable converter such as the Progressive Dynamics PD9000 series, it will keep them maintained properly if the unit is plugged in.
However, in my opinion it is best to use a small charger/maintainer that is designed for AGM batteries. Using a typical 2 amp trickle charger is not sufficient, rather one that can be programmed for the AGM charging profile.
Lithium Iron Phosphate (LiFeP04)
The Lithium battery has become the “hot” battery recently as it will not sulfate, has a cycle rate of anywhere from 5-10K which means it could last for 10 years or more, and can be drained to 100% of it’s power capacity known as amp hours.
The downside of Lithium besides the cost, is it needs a 14.4-volt charge which most converters/chargers do not have, and can not be charged in below-freezing temperatures without some type of heater which is usually controlled by a battery management system (BMS) within the battery. That of course is only with the good Lithium Batteries which is a select few.
I have posted several articles about swapping out your standard FLA and AGM batteries for Lithium and what is required for charging, temperature control, and even DC to DC converters so we will not go into that, however I found the best thing to do for storing Lithium Batteries is to simply disconnect the negative cable or cables depending on your configuration. According to Go Power, Expion 360, Battleborn, and others that supply the RV industry, the Lithium battery will only draw down less than 1% in 6 months if there is no draw on the battery such as an LP leak detector. If you disconnect the negative cable, there will be no draw at all.
About the author: Dave Solberg: Managing Editor, RV Repair Club
For the last 25 years, Dave has conducted RV maintenance and safety seminars, developed dealer and owner training programs, written RV safety and handyman articles authored an RV handbook reference guide, and logged over 100,000 miles on the road in an RV.
RV Repair Club is your go-to online resource for enthusiasts who want quality RV maintenance, repair, and upgrade information – a community where passionate RVers can come together to gather knowledge and share their experiences.
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