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Polk’s Top 7 Tips for Saving your RV Batteries

Mark Polk, motorhome maintenance expert

By Mark Polk
RV Education 101  

Did you know that almost 85 percent of all 12-volt batteries manufactured in the United States will die before they should? 

The two most common causes for RV battery failure are undercharging and overcharging.  Undercharging is a result of batteries being repeatedly discharged and not fully recharged between cycles. If a battery is not recharged the sulfate material that attaches to the discharged portions 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. Sulfation is the number one cause of battery failure.

The second leading cause of battery failure is overcharging. Overcharging batteries results in severe water loss and plate corrosion. This is especially true when it comes to RV batteries. The RV converter has a built-in battery charger. Most owners are under the impression that if you leave the RV plugged in when it is being stored, the converter will keep the batteries topped off.

The problem is many converter chargers provide a constant charge of about 13.5 volts, which is too high for fully charged batteries, and the electrolyte is boiled off. The result is an early death for the batteries. The good news is both of these problems are avoidable.

Here are my Top 7 quick tips to help prevent your RV batteries from becoming a statistic.

1. Sulfation will occur when a battery’s state of charge drops below 80 percent, or 12.4 volts. Recharging a battery at an 80 percent state of charge will prevent sulfation. Using a battery charger, maintainer and conditioner like the Battery Minder will prevent sulfation, too.

2. Never let a battery discharge below 10.5 volts.

3. Reducing the battery’s depth of discharge will increase the life of the battery. A battery discharged to 50 percent every day (50 percent capacity remaining) will last twice as long as it would if it’s cycled to 80 percent (20 percent capacity remaining).

4. RVs have parasitic loads that will discharge the battery over time. Some, but not all, of these loads are LP-gas leak detectors, the TV antenna power booster, clocks, stereos and appliance circuit boards. If your RV is equipped with a battery disconnect switch, make sure it is in the OFF position when you’re not using the RV or when it is in storage. Batteries in storage will self discharge. It’s not uncommon for a battery to discharge up to 10 percent a month. Check and recharge batteries in storage as required.

5. Hot temperatures and overcharging kill batteries. During hot weather or during high usage check the batteries frequently. Checking the electrolyte levels and adding distilled water as required can save your lead acid batteries.

6. Properly charging your batteries needs to be done in stages. A bulk charge should be performed to return the battery to 90 percent of a full charge in the first few hours. An absorption charge is used for the remaining 10 percent, and then a float charge to keep the battery fully charged.

7. Batteries should only be watered after charging, unless the plates are exposed prior to charging. If the plates are exposed, add just enough water to cover the plates. To get a quick picture of the battery’s condition, use a digital voltmeter. A fully charged battery should read about 12.7 volts. A battery reading of 12.4 volts or less should be charged to prevent sulfation. The battery should only be tested after resting for 12 hours. Resting means it has not been charged, or had a load placed on it over a 12-hour time period.

The sad news is most RV batteries only last two to three years. Through some routine maintenance and following some of these quick tips, you can double the life of your RV batteries.

A final note: The lead and plastic used to construct batteries can be recycled. More than 97 percent of all battery lead is recycled. Be sure to recycle your old batteries.

Happy Camping.

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