It’s not uncommon for RV batteries to die long before they should. A report I recently read stated 85% of lead-acid batteries manufactured in the U.S. die before they should. And I see it all the time, RV owners replacing batteries every year or two. That can get expensive real fast.
Sometimes we tend to overlook the simplest maintenance requirements on our RV, and these maintenance oversights can be costly. I put RV batteries on top of the list for items on the RV that are commonly overlooked. Fortunately if you understand what kills a battery, and perform some simple battery preventive maintenance you can stop the batteries from dying an early death.
Let’s look at some of the factors that contribute to battery failure:
- Sulfation
- Parasitic loads
- Self-discharging
- Overcharging
- Undercharging
- Lack of maintenance
We’ll start with the number one cause for lead-acid battery failure, sulfation. When you use a battery small crystals of sulfuric acid start forming on the plates in the battery. This is normal and when the battery is charged on a regular basis these crystals convert back into active plate material. The problem starts when a battery remains in a low state-of-charge for an extended period of time. Sulfation starts to form on plates when a battery drops below 12.5 volts. The longer a battery remains in a low state-of-charge condition the larger the sulfate crystals get until the sulfate cannot be converted back into active plate material and the battery is ruined. This can happen regardless if the battery is 1-year-old or 7-years-old. The important thing to remember is to always recharge a discharged battery in a timely manner.
This is where things start to get interesting. You can recharge the batteries in a timely manner to prevent sulfation, but other factors come into play too. There are numerous electronic devices and equipment in your RV that can drain the battery when you are not using the RV. These are referred to as parasitic loads and they slowly drain the battery, even when you are confident nothing was left on in the RV. Some examples are the TV antenna booster, the LP gas leak detector, clocks in stereos, electronic circuit boards, or accidentally leaving a 12-volt light on in the RV. Your automobile has the same type of parasitic drains on the battery, but it doesn’t drain the battery because you drive the vehicle and recharge the battery on a regular basis. In your RV it’s possible for these parasitic loads to drain the battery when you don’t use or charge the battery for long periods of time. And remember as soon as the battery state-of-charge drops below 12.5 volts sulfation starts, and if the battery stays in that condition for an extended period of time the battery will die. It’s a vicious cycle!
Another interesting dilemma not every RV owner is aware of is that batteries self-discharge while in storage. It’s not uncommon for a battery to discharge up to 10% a month in storage. At this rate it won’t take long to completely discharge the battery, and you guessed it if the battery is not recharged sulfation starts forming and the battery will die.
Next on the list is overcharging the battery. Your RV has a converter with a built-in battery charger. Converter charger technology has improved in recent years and the majority of modern day converter chargers are sophisticated 3-stage battery chargers. The first stage is a bulk charge used to return the battery to about 90% of a full charge. The second stage is an absorption charge used for the remaining 10 percent. This stage is designed to help prevent battery gassing and loss of water. The third stage is a float or maintenance charge to keep the battery in a fully charged condition. The float charge is roughly 13.2 volts and it prevents the battery from overcharging. Maintaining a float charge on the battery is extremely important, but the problem is older and less expensive RV converter chargers provide a constant charge of about 13.5 volts. This charge rate is too high for fully charged batteries and the electrolyte is eventually boiled off as the battery continues to charge, resulting in an early death for the battery. The only way to prevent this is through routine battery maintenance. To save your RV batteries and your wallet you need to periodically check and adjust the water level in the lead-acid batteries. This simple preventive maintenance check can save, and extend the life expectancy of your batteries. If you do need to add water to the battery only use mineral free water. Distilled water is best. Fill the battery cell to 1/8 inch below the vent well. Note: Always wear rubber gloves and eye protection when working around lead-acid batteries.
Let’s briefly discuss prevention. We know how important it is to recharge a discharged battery, especially while sitting in storage for extended periods of time, but how do we do it? One recommendation is to plug the RV in for about 8 hours every month to recharge and top the batteries off. But, not everybody has a place to plug the RV in. Another recommendation is to remove the batteries when the RV is in extended storage and store the batteries too. The problem with this is you still need to test the battery state of charge every month (remember batteries self-discharge) and recharge any battery that is at or below a 70% state of charge. A third recommendation is to purchase some type of battery maintainer & conditioner like a Battery Minder or Battery Tender product that you can leave connected to the batteries without concern of overcharging. Last but certainly not least, you can use and enjoy the RV once a month and let the batteries get charged that way.
If your RV has battery disconnect switches make sure they are turned off when the RV is stored. This will prevent parasitic loads from draining the batteries. Check the state of charge on a regular basis, and after the batteries have charged check the water levels. The bottom line is a little routine maintenance and recharging a discharged battery as soon as possible will extend the life of the battery. RV batteries can and should last 5 to7 years, rather than 1 to 2 years. Now you can use the money you save on replacing batteries and take an extra RV trip or two this camping season.
Happy Camping,
Mark J. Polk
RV Education 101
