There is really only one main cause for battery failure…sulfation. And there are two main reasons why sulfation occurs; that is overcharging and undercharging your battery. Understanding the charging needs of your RV battery will help you extend its life and save you money.
Sulfation is when sulfate crystals build up on the plates of the lead acid battery. This happens with all standard batteries. Batteries will develop sulfation every time they are discharged and recharged. Where it becomes abnormal is when there is a rapid development of sulfation caused by overcharging, undercharging or letting a battery sit for too long. This rapid sulfation can happen in just a couple days’ time if overcharged or undercharged. Even temperature can cause your battery to discharge and sulfate rapidly if stored in 75 degrees or higher (Keep in mind that your battery discharge rate will double for every 10 degree increase above room temperature (Which is roughly 68-75 degrees).
Undercharging is when your batteries are being discharged or used and are not being fully recharged between the cycles. If your battery is not recharged fully, the sulfate that attaches itself to the discharged space of the plates begin to crystallize. If this happens for long enough, the sulfate cannot convert back and it blocks the charge. This can also occur if you keep your battery discharged for long periods of time. Under charging is the number one cause of battery failure.
Overcharging batteries can have a different affect but same result in rendering your battery useless. If you over charge the battery it will cause the battery to lose water and increase its plate sulfate corrosion.
- Use your battery disconnect when the RV is in storage or not in use (Some appliances will draw from your battery even if the appliance is not running)
- Sulfation occurs when a battery’s charge is below 80 percent (12.4 Volts). To prevent sulfation, charge your battery at 80 percent and make sure it gets a full charge (That is 20% cycled or used). Charging at lower levels can significantly decrease your battery’s life but make sure to never let your battery reach 10.5 volts
- Monitor your battery voltage by checking your inverter or solar panel battery monitor display. Or you can check your battery with a voltmeter. To get a good read with the voltmeter, the battery should be at rest for 12 hours (No use and no charging). The battery should read 12.7 volts. If it is 12.4 or below it needs charged
- A sitting battery can discharge up to 10% a month. Every month check the charge of your battery and fluid levels (Add using only distilled water to your battery fluid to make sure the fluid is just covering the plates. Don’t add fluid before charging or it can cause the fluids to overflow). This should be done in cold or hot weather. In really hot temperatures, it may be wise to check them more frequently
- Charging your battery should be done in three stages (Bulk, Absorption and Floater stages). The Bulk charge is a constant charge with increases in voltage to 80% capacity. Then the Absorption charge will charge the remaining 20% at an absorption rate (At charger set points). The Floater charge is at a reduced voltage and held constant. The current is then reduced to 1 percent capacity to maintain a fully charged battery. All this can be made easy with a Smart Charger. (If you can, always follow manufacturer instructions for charging and maintaining your battery). Most manufacturers ask that you charge with a charger that is 25% amp hour capacity of your battery
- If unhooking and hooking your batteries, always unhook the negative first. When hooking back up hook up the positive first then the negative.
- Remove all corrosion from the battery terminals using a mixture of baking soda and water, a wire brush and then clean off the battery (This will help eliminate potential discharge)
- When storing your RV, consider taking the batteries home with you. So you can more easily care for them ( Check your battery once a month)
- If leaving the battery with the unit be sure that it is fully charged and to completely disconnect the battery to avoid any draws from appliances
- Never use the built in charger when the RV is in storage. It will burn out your battery
- Check the voltage every month and charge it if it falls below 80%
- Store batteries in a cool, dry place with temperatures between 32°F – 80°F
- Never allow your battery to freeze and never attempt to charge a frozen battery
When well maintained your deep cycle batteries can last up to 5 years.
Written by: Robert Norman