Since there are so many different manufacturers out there, a blanket recommendation on how to maintain a battery bank may not always work for your particular setup. Consult your RV's owner's manual for specific instructions, and if your batteries have their own manual, check that out too. If you don't have manuals on hand, check the manufacturer's website to see if you can download a copy for future reference!
One of the easiest and most effective ways to ensure that your battery bank stays working properly is to keep the batteries properly charged. Over- or undercharging batteries will affect the inner workings of your batteries, leading to premature failure. This is easily avoidable by charging the batteries every few days. As a general rule of thumb, you'll want to avoid deep discharge—that is, low battery power charge levels. Allow the battery to discharge to 50 percent, but don't let it discharge any further. Fifty perfect discharge seems to be that sweet spot that actually extends the life of your battery bank! Just remember, batteries will lose their charge even when you're not using your RV, so make sure to charge the batteries while your RV is in storage. Keeping RV batteries charged can also be more of a challenge to those of you who have a solar power setup, as you can't always expect a sufficiently sunny forecast every single day, so you'll want to plan ahead to keep your batteries charged up.
Just like improperly charging, subjecting your RV's battery bank to extreme temperature can damage battery components, leading to power failure and the need for replacement. In extreme heat, batteries are subject to sulfation, which is the formation of sulfate crystals on the negative plates, which reduces the battery's active material and is the number one cause of failure in lead acid batteries. On the other end of the spectrum, an undercharged battery can freeze in extreme low temperatures, so adding some extra insulation around the battery bank might be a must if your RV will be subject to extreme cold.
It's imperative to know how much power you use in your RV, the amp limit of your battery bank, and how long you'll be able to run your RV on the battery. To avoid damage to the battery or your electrical system, purchase a battery with the proper amount of charging capacity for your RV. If you have a 12V system, you'll want to buy a 12V battery for your RV! Even if you'd like to connect multiple batteries together, you'll want to ensure that each battery has the same voltage as well. You should also note that in addition to avoiding mixing battery voltages, you should never mix and match old batteries either, as this will lead to uneven charging, which wears out new batteries faster!
Battery power can definitely be something we take for granted, especially when that power runs out and we're left in the dark! First and foremost, check your battery for any signs of distress or damage. Regularly check the battery charge level, every few days or so, to ensure that you aren't discharging it too deeply. Also be sure to check the electrolyte level from time to time. Electrolytes allows electrical charge to flow through the battery and provide energy to electrical components. It is also important to check the water levels monthly, or bi-monthly if you're using a converter. Use only mineral-free, or ideally distilled water, and make sure not to overfill the cell to avoid damage to the battery.