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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. The good news is both of these problems are avoidable.
Before we talk about battery maintenance 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're charging is very explosive. When you work around batteries you need to wear goggles and gloves, remove all jewelry and do not smoke or use any open flames. Caution: If you accidentally get battery acid on your skin, flush it with lots of water and if it gets in your eyes you need to flush with low pressure water for 15 minutes and call a doctor.
Battery maintenance is actually very simple. By performing these maintenance procedures every three to six months you can extend the life expectancy of your RV batteries. You should make these checks more often in hot temperatures or during heavy battery usage.
The first thing we want to do is visually inspect the battery for any obvious damage. Any fluid on or around the battery may be an indication that electrolyte is leaking from the battery. A damaged or leaking battery should be replaced immediately. Inspect the battery terminals, cables, and connectors for any damage and for good connections. Look for any signs of corrosion. Corrosion can be neutralized with a 50/50 mixture of baking soda and warm water. Clean any dirty battery terminals and the insides of cable clamps with a post and clamp cleaner. If you remove any battery cables always disconnect the negative battery cable first. When you reconnect the clamps to the terminals connect the positive cable first. Never over tighten the battery terminals. Over tightened terminals can result in broken battery posts, post meltdown and / or fire. When you finish making the connections spray the clamps with a battery terminal protector.
Checking the electrolyte level on a regular basis can save your flooded lead acid batteries. Check the water level monthly and if you leave your RV plugged in with the batteries being charged by the converter battery charger check it bi-monthly. If your converter doesn't have a three stage charger the battery is getting a constant charge of 13.5 volts. When the batteries are topped off this voltage is too high for a float charge and it can boil off the electrolyte over time. When you add water only use mineral free water. Distilled water is best, and only fill the cell to 1/8 inch below the fill well. Overfilling cells will cause battery acid to overflow. When this happens the battery will lose some of its capacity and corrosion will build up on and around the battery. Water should only be added after fully charging the battery unless the water level is below the plates.
Follow these steps for watering the battery. Remove the vent caps and look inside the fill wells. Check the electrolyte levels. The minimum level required for charging the battery is at the top of the plates. If it's below the plates add enough distilled water to cover the plates before you charge the battery. Fully charge the battery before adding more water. When the battery is charged remove the vent caps and check the electrolyte levels. Add distilled water until electrolyte level is 1/8 inch below the fill well. Replace and tighten all vent caps. Warning: Never add battery acid to a battery.
Visual inspections of our RV batteries are important, but that won't tell us the actual condition of our batteries. We need to test the batteries to determine their state of charge and overall condition. There are a couple of different ways to check your batteries state of charge. You can measure the voltage with a digital voltmeter or check the specific gravity of the acid with a hydrometer. Testing the specific gravity is the preferred method but measuring voltage has its advantages. If you have sealed batteries your only choice is to measure voltage and measuring voltage can give you a quick picture of the batteries depth of discharge so you know when they need to be recharged.
If the battery state-of-charge is below 70% the battery needs to be recharged before you test it. The battery should not be tested if it has been charged or discharged in the last 6 hours and preferably 24 hours. This is called an open circuit voltage test. To measure the voltage you need a good digital voltmeter.
Whenever possible you should avoid discharging a battery below 40%. Battery readings that are off of this chart indicate the battery was left discharged too long or the battery may have a bad cell.
Happy Camping!
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