The two most common causes of RV battery failure are insufficient charge and overcharging.
Insufficient charging is the result of batteries repeatedly discharging and not fully recharging between cycles. If a battery is not recharged, the sulfate material that clings 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 a long 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 the batteries results in great water loss and plate corrosion. With that said, let’s see how to properly store your RV batteries.
Before talking about battery storage, we should talk about battery safety. Lead batteries contain sulfuric acid which is extremely corrosive and can cause severe burns or even blindness. And the hydrogen gas that batteries produce when charged is highly explosive. When working with batteries, you should wear protective glasses and gloves, remove all jewelry, and do not smoke or use open flames.
Bail: If battery acid accidentally comes into contact with your skin, rinse it with plenty of water and, if it gets in your eyes, rinse with low pressure water for 15 minutes and call a doctor.
When storing the RV for the long term, it is a good idea to remove the batteries and store them as well. This is very easy to do. The first thing we want to do is visually inspect the batteries for obvious damage. Any liquid on or around the battery can be an indication that there is an electrolyte leak from the battery. A damaged or leaking battery should be replaced immediately. Whenever removing a battery, always remember to remove the negative terminal or cable first, and then the positive cable.
Battery Tip: When removing a battery, turn off the power switch, all electrical switches, and any battery disconnect switches before disconnecting the battery cables. Whenever you remove the cables from the battery, label them first so you remember how they return to the battery. When reinstalling the battery, do it in reverse order. Install the positive cable first and then the negative cable.
Clean the batteries with a 50/50 mixture of baking soda and water if necessary, that is, use one pound of baking soda for every gallon of water. Now you can 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 under the plates, add enough distilled water to cover the plates before charging the battery.
Test the battery state of charge with a voltmeter or hydrometer and charge batteries that are 80% or less. An 80% load 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 falls 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 the 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 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% a month when stored. Low temperatures slow down this natural discharge process and warmer temperatures speed up the process. Try the
stored the battery state of charge every month and charge batteries that are 80% or less of the state of charge.
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 sulfate back to its original components.
If you decide 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 multi-stage converter RV chargers and aftermarket chargers are designed to maintain a floating charge in 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, check out our Deep Cycle Battery Care and Maintenance DVD.
Happy Camping,
Mark polk
Copyright 2007 by Mark J. Polk, Owner of RV Education 101