The two most common causes of RV battery failure are undercharging and overcharging.
Undercharging is the result of batteries being repeatedly discharged and not being fully recharged between cycles. If a battery is not recharged, the sulfate material that adheres to the discharged parts of the plates begins to harden into crystals. Over time, this sulfate cannot be converted back into active plate material, and the battery is ruined. This also occurs when a battery remains discharged for an extended period of time, such as during storage. Sulfation is the leading cause of battery failure. The second leading cause of battery failure is overcharging. Overcharging of batteries results in severe water loss and plate corrosion. With that said, let’s look at how to properly store your RV batteries.
Before we talk about battery storage, we need to talk about battery safety. Lead acid batteries contain sulfuric acid which is extremely corrosive and can cause severe burns or even blindness. And the hydrogen gas that batteries produce when they are charging is highly explosive. When working with batteries, you must wear protective glasses and gloves, remove all jewelry, and do not smoke or use open flames.
Bail: If you accidentally get battery acid on your skin, rinse with plenty of water and if it gets into your eyes, rinse with low pressure water for 15 minutes and call a doctor.
When you put the RV in long-term storage, it’s a good idea to remove the batteries and store them as well. This is quite simple to do. The first thing we want to do is visually inspect the batteries for any obvious damage. Any fluid on or around the battery can be an indication that electrolyte is leaking from the battery. A damaged or leaking battery must be replaced immediately. Whenever you remove a battery, remember to remove the negative terminal or cable first, then the positive cable.
Battery Tip: When removing a battery, turn off the ignition switch, all electrical switches, and any battery disconnect switches before disconnecting the battery cables. Any time you remove the cables from the battery, label them first so you remember how they come back to the battery. When reinstalling the battery, do it in the reverse order. Install the positive cable first and then the negative cable.
Clean batteries with a 50/50 mixture of baking soda and water if necessary, i.e. use one pound of baking soda to one gallon of water. You can now check the electrolyte level in each cell and add distilled water if necessary. The minimum level required is at the top of the plates. If it is below the plates, add enough distilled water to cover the plates before charging the battery.
Test the state of charge of the battery with a voltmeter or hydrometer and charge batteries that are 80% or less. An 80% charge is approximately 12.5 volts for a 12 volt battery and 6.25 volts for a 6 volt battery. Lead sulfation begins when the battery’s state of charge drops below 80%. After charging the batteries, check and fill each cell to 1/8 inch below the fill well with distilled water. Overfilling the cells will cause battery acid to overflow.
Bail: Batteries should only be charged in a well ventilated area and keep sparks and open flames away from the battery being charged. Check electrolyte levels before and after charging batteries.
A discharged or partially charged battery will freeze much faster than a fully charged battery. Store batteries in a cool, dry place, but not where they can freeze. Stored batteries will lose a percentage of current through internal leakage. It is not uncommon for a battery to discharge up to 10% per month when in storage. Cold temperatures slow down this natural discharge process and warmer temperatures speed it up. try the
the state of charge of the stored battery every month and charge batteries that are at 80% or less.
Fully charge the batteries before reinstalling them next spring. For optimal performance, you can equalize the batteries after they are fully charged. An equalization charge is an increase in charge voltage similar to a bulk charge to convert any crystallized lead sulphate back to its original components.
If you choose to leave the batteries in the RV while it is in storage, remember to check the state of charge monthly and charge the batteries to 80% or less. Some RV Inverter Multi-Stage Chargers and aftermarket chargers are designed to maintain a float charge on the battery without removing the batteries from the RV. Remember, for the converter charger to work, the RV will need to be plugged into electricity.
For more information on RV batteries, see our Deep Cycle Battery Care and Maintenance DVD.
happy camp,
mark polk
Copyright 2007 by Mark J. Polk, owner of RV Education 101