Understanding Your RV Battery by Mike Wilson

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The batteries in your RV are the “heart” of the electrical system. Good batteries with the proper charge are important for many reasons. There are a variety of items that depend on battery power to function.

In an RV, the batteries power basic items such as lights and water pumps.

Batteries also power many items you may not think of, such as the electronic igniter for the water heater, roof vent electric fans, the antenna booster for the TV, the L.P. gas valve for the refrigerator, the L.P. gas leak detector, the furnace blower, and an inverter if you have one.

It is important that battery charge level be maintained for proper operation of items. When the charge level gets low, available voltage may not be enough for electronic items to operate correctly. Some items, such as the furnace blower will simply slow or stop. Other items, such as the refrigerator may act erratic, stop operation, or even damage the electronic circuit board.

Proper battery maintenance is essential. Battery electrolyte level should be checked at regular intervals. I recommend checking the level when the oil change is performed. In addition, electrolyte level should also be checked when the RV is connected to shore power for extended periods. Most built in RV chargers operate continuous. This may overcharge the batteries. Overcharging can cause the electrolyte to overheat and in some cases boil. This will cause the electrolyte level to drop. Low electrolyte or complete loss of electrolyte can cause battery failure. It may be necessary to remove the batteries to check the electrolyte level. CAUTION: Be certain to wear latex gloves and eye protection when checking electrolyte levels. Be careful with wiring if removing.

Many times positive and negative wires are not marked or color coded. Take the time to mark each and every wire. I use masking tape and a sharpie. I also draw a picture of exactly how each battery is installed. I cannot tell you how many times I have had to straighten out someone’s mess from improper battery connections. (usually causes catastrophic component failure)

When replacing RV batteries it is important to install the proper type of battery. Campers should have “deep cycle” batteries. These batteries are constructed differently than a typical car starting battery. They are designed to be discharged and recharged. They typically have a higher reserve capacity (slower discharge) rate than a starting battery. Starting batteries should be used for the chassis battery of a Motor Home. Cranking amperage or cold cranking amperage is higher in a starting battery. This is important to start an engine, but is not important for the coach or camper. In some cases, the coach or camper batteries are used to start the gasoline powered generator. A deep cycle battery has plenty of amperage to start a generator.

There are several battery types that may be used in an RV.

1.Flooded batteries have liquid electrolyte in them. They are typically the least expensive and work fairly well. Outside ventilation is required. Corrosion from electrolyte leakage is the most common problem.

2.Sealed Gel batteries are another option. Costs are higher than flooded batteries. Maintenance is not required. Ventilation is not required. Corrosion is usually not a problem. Longevity is comparable to a flooded battery.

3.AGM (absorbed glass mat) is another option. AGM batteries do not require ventilation and will not corrode. AGM batteries typically last longer than flooded or gel batteries. There is no maintenance. Discharge and recharge rates are better. Costs are higher.

Proper battery testing methods are important. Deep cycle batteries typically have shorter warranty periods than starting batteries. This is due to construction, design, and use.

I recommend testing the batteries at least once a year. I test all mine before use in the spring.

Any battery MUST be properly charged before testing. Testing should be done by a professional. The electrolyte specific gravity must be checked to be certain the battery is fully charged before load testing. An automated electronic load tester may be used. I still use my reliable carbon pile tester. If your batteries test weak or bad, be certain to replace them. A weak battery will likely fail during extreme conditions, usually under heavy use or extreme temperatures. In applications with multiple batteries, be certain to replace all batteries at the same time.

Proper battery care during storage is important. Batteries should not be discharged. A discharged battery may freeze during cold weather. Be certain not to overcharge. Remember, leaving the power cord connected for extended periods can overcharge the batteries.

Many times RV’s have a parasitic drain. A parasitic drain is an item that continues to draw amperage when the RV is not in use. For this reason, I recommend disconnecting the batteries during storage. You can disconnect with a switch if your RV has it, or remove all battery cables from a post. I also recommend an automatic battery charger be used during storage. This type of charger can be left on the batteries continuously.

Above all, use common sense and always take proper safety measures.

About the Author: Mike Wilson is a RVDA Certified Master RV Tech. Mike has 25 years experience as an RV Technician and now he's sharing his knowledge with you.
Mike is the president of Wilson RV and developer for The RV Help Desk