RV Repair Manual
for the RV Do-It-Yourselfer
The life expectancy of your RV batteries depends on you. How they're used, how well they're maintained, how they're discharged, how they're recharged, and how they are stored all contribute to a battery's lifespan. A standard battery cycle is one complete discharge from 100% down to about 50% and then recharged back to 100%.
One critical factor in battery life is how deeply the battery is cycled each time. If a lead-acid battery is discharged down to 50% every day, it will last twice as long as it would if cycled down to 80% Depth of Discharge (DoD). Keep this in mind when considering a battery's amp-hour (Ah) rating: your usable capacity is really half the rated total because you don't want to completely drain flooded lead-acid cells before recharging. Tracking state of charge with a digital RV battery monitor with shunt helps prevent over-discharging.
Rule of Thumb: Recharging a discharged battery as soon as possible prevents sulfation buildup on internal plates, significantly extending overall service life.
What does all of this mean to you? That depends on how you use your RV. If most of your camping is done where you're plugged into shore power, your main concern is simply maintaining your deep-cycle batteries by topping cells off using a distilled water battery filler bottle and keeping them topped up using a multi-stage smart battery charger.
If you prefer boondocking and dry camping off-grid, you'll want the highest amp-hour capacity you can fit on your coach.
Deep-cycle batteries come in various physical footprints designated by BCI group sizes, such as Group 24, Group 27, and Group 31. Generally, the larger the battery casing, the higher the amp-hour yield. A single 12-volt Group 24 battery provides roughly 70 to 85 amp-hours. Wiring two 12V batteries in parallel doubles your amp-hour capacity while keeping the system at 12 volts.
If space permits, many experienced RVers upgrade from standard 12V marine/RV batteries to a pair of heavy-duty 6V golf cart batteries (GC2). Wiring two 6V batteries in series creates a robust 12V bank with thicker lead plates designed for heavy cycling. If you need even more power, building a four-battery bank wired in series-parallel delivers 12 volts with double the usable capacity.