Your RV lead acid batteries are one of the most important components of your RV. They store the energy needed to start your vehicle and ensure you can enjoy creature comforts like a warm shower, charged cellphone and a cold drink. By learning about and caring for your batteries, you will extend their lifespan.
How Lead Acid Batteries Work
All rechargeable lead acid vehicle and house batteries have alternating lead plates (cathode) and lead coated with lead dioxide plates (anode) that are bathed in a 65% water and 35% sulfuric acid solution called electrolyte. When lead combines with the sulfate in the electrolyte solution, it creates lead sulfate, water and electrons. The chemical reaction releases electrons that flow through the conductors to produce electricity. As the battery discharges, the lead sulfate collects on the battery plates until the chemical reaction is reversed by recharging the battery. The lead sulfate is removed from the lead plates and joins the electrolyte solution.
Each 12-volt battery has six galvanic cells in a series producing two volts of electricity each for a total of up to 12.7 volts of power that are available when the battery is fully charged. A simple task such as turning on the lights in your RV will pull stored electricity from your RV house batteries. Starting your RV to drive down the road will use stored electricity from your vehicle battery. Your RV house charger replenishes your house batteries when plugged into shore power, whereas your vehicle battery is recharged by driving.
Batteries are wired into a series or parallel configuration. Serial wiring increases voltage, not amp hours. Parallel wiring increases amp hours, not voltage.
Batteries to Run Your Vehicle and Your House on Wheels
Vehicle Batteries – These “cranking” batteries are designed to start your vehicle. They provide huge amperage in a short burst to get your engine going. CCA, cold cranking amps, measures the number of amps a battery can deliver at 0° Fahrenheit for 30 seconds and do not drop below 7.2 volts. Vehicle batteries are measured in amps and volts. These batteries have a greater number of plates than RV house batteries.
RV House Batteries – The batteries that provide your RV 12-volt household power needs offer a smaller amperage over a longer period of time than your vehicle battery. The house batteries are often heavily discharged before being fully recharged. This has earned them the name of “deep cycle.” RV house batteries are measured in volts and in AH, amp hours, which are the total number of amps of power the battery can deliver over a 20-hour period. The AH on RV house deep cycle batteries ranges from 30 to well over 200 AHs, depending on the type of house battery. Most RVs have two or more house batteries arranged in either a serial (if each battery is 6-volts) or parallel (for the 12-volt types) configuration. You may have multiple banks of batteries in your RV.
Marine Batteries – These batteries are designed for short burst usage and also provide “house” deep cycling amperage. These batteries are often less expensive than deep cycling RV house batteries. However, they are trying to suit two needs, so although they may be less expensive than deep cycling lead acid RV house batteries, the marine batteries are not as efficient at delivering house electricity.
Types of RV House Batteries
There are three types of deep cycling batteries that are commonly deployed for RV household use.
- Flooded cell batteries – These batteries have a cap covering each cell and require water to be added, as needed.
- Gel batteries – A thick paste of electrolyte is used in these sealed valve regulated lead acid batteries. These batteries are sealed and do not need any additional water to be added. Gel batteries are slower to charge than flooded cell batteries.
- AGM (absorbed glass material) batteries – These batteries retain their electrolyte solution in a sponge made of glass fibers. These valve regulated lead acid batteries are sealed and do not need any additional water to be added.
Life Shortening Problems with RV House Batteries
Most deep cycling batteries last from six months to 48 months based on usage, maintenance and the environment. There are two problems that shorten battery lifespan.
Undercharging – This is the leading cause of shortened battery life. Sulfation results when the process of returning the sulfite that has gathered on the battery plates is not fully reversed by charging. The sulfur on the plate crystalizes and hardens on the plates. This throws the balance of the electrolyte off since the acid is not being recovered. This can also happen when a battery is stored for a long period of time. Be sure to fully recharge your batteries before they are 50% discharged, rather than only charging to less than 80% of capacity. Never let your battery discharge below 10.5 volts.
Overcharging – When your RV house battery is overcharged, the electrolyte is boiled away, causing severe water loss and corrosion on the plates in the battery. If your RV converter provides a constant charge of up to 13.5 volts when you are on shore power, you may need to increase your battery maintenance checks, adding water more frequently. Test your battery voltage by using a digital volt meter.
RV House Battery Safety
When working with RV house batteries, keep in mind these safety basics. Refer to your battery owner’s guide and make sure to observe all guidelines from the manufacturer.
- Always wear protective safety googles/glasses.
- Always wear protective gloves.
- Remove all jewelry.
- Disconnect the black negative cable from your battery before disconnecting the red positive cable.
- RV house batteries in use should always be vented to the outside since they can produce hydrogen gas.
- Never add acid to a flooded cell battery.
- All damaged or leaking batteries should be replaced immediately.
- Never attempt to charge a battery that is damaged or frozen.
- Never attempt to charge a battery that is hot to the touch.
- Never insert a metal thermometer into a battery cell. This could result in an explosion.
- Properly dispose of all retired batteries. The batteries are considered hazardous waste.
RV House Battery Maintenance
Follow your battery manufacturer’s guidelines for maintenance. Here are some basic guidelines that may apply based on your battery type and the environmental and usage conditions. Heat from either the environment or excessive usage will accelerate corrosion.
- Disconnect batteries and clean battery posts and terminal connections. There are specialized battery brushes available.
- Tighten and lubricate terminal connections to prevent oxidation and minimize corrosion. Use an anti-corrosion spray or dielectric grease based on your manufacturer’s recommendation.
- Add water to flooded cell batteries. Generally, the added distilled water should not exceed 1/8 to ¼ inch above the lead plate. These batteries lose some water every time they are charged.
- Completely charge your batteries before storing your rig. As part of your storage process, also disconnect all electric connections, including the serial or parallel connectors. This is extremely important since many RV appliances pull current even when they are turned off. Monitors, detectors and entertainment devices all contribute to drawing down the charge levels if the battery remains connected. Even when disconnected your battery will lose some of its charge each month it is in storage. Flooded cell batteries lose their charge at a faster rate than sealed batteries. It is a good idea to reconnect the battery and charge it during the storage period, restoring it to fully charged status.
- Test the conductivity of your battery by using a digital voltmeter after 12 hours of non-usage and non-charging. Load testing can be done at an auto parts store.
- Equalizing batteries – Sulfite crystals can be loosened from the lead plates by performing a controlled overcharge of flooded cell batteries. Each cell’s state of charge can be checked by using a battery hydrometer. Carefully follow the manufacturer’s instructions and safety guidelines if attempting this maintenance on a flooded cell battery.
Buying New RV Batteries
When a house battery fails, it is best to replace all the batteries at the same since they work together.
When you are shopping for RV vehicle and house batteries, note the offered warranty. In many cases the battery will not function for the full warranty period. You may be able to apply a rebate on your new battery purchase.
Also, be prepared for sticker shock when you see how expensive new deep cycling batteries are when compared to vehicle batteries. If you are ready to shop for new house batteries, be aware of the amp hours you want and need as well as the space you have in your battery compartment. Some batteries with higher amp hours are bigger than the lower amp hour batteries. Also be aware of the electrical cabling you have: serial or parallel configuration.
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