Understanding your RV battery bank
The direct answer for a typical boondocking rig
An RV using 1,800Wh a day for 3 days of boondocking needs about 562Ah at 12V with an 80% depth of discharge LFP battery, which rounds up to three 200Ah batteries or two 300Ah batteries for 600Ah total. That bank weighs approximately 80 to 90 pounds with LFP chemistry, a fraction of what an equivalent lead-acid bank would weigh. The real comparison is against a grid connection. The payback period calculator in our Savings & Payback section can help you weigh the system cost against what the grid would charge.
Why weight matters more for RVs than any other off-grid build
Every RV has a cargo carrying capacity (CCC) printed on a manufacturer sticker, usually near the entry door or in the owner's manual, and everything you carry, batteries included, counts against that number. A large lead-acid bank can weigh 250 pounds or more, eating a significant chunk of payload on smaller trailers and vans before you've packed anything else. This is one of the strongest practical arguments for LFP in an RV specifically, separate from its depth of discharge advantage. The lithium vs lead-acid comparison tool in our battery chemistry storage tools compares the two chemistries side by side beyond just this weight question. Panels are only half an off-grid system. The backup runtime estimator in our Battery & Storage section sizes the battery bank your daily load needs to get through cloudy stretches.
Boondocking days versus autonomy days
Unlike a stationary cabin or home, an RV's "boondocking days" figure usually accounts for some daily solar recharge happening alongside battery draw, not zero solar input like a pure autonomy calculation. If you want a stricter zero-sun worst case, the battery only autonomy calculator handles that scenario directly. Most boondockers use this looser boondocking-days framing since it better matches how they actually travel and camp. Battery economics referenced throughout trace back to the National Laboratory of the Rockies Annual Technology Baseline.
Matching the battery bank to your solar and inverter
A battery bank sized well beyond what your solar array can recharge in a reasonable window, or beyond what your inverter can safely discharge, creates a mismatched system. Check the RV solar wattage calculator to confirm your panels can keep up with this battery size, and the inverter sizing calculator to size the AC side correctly. The DOE's overview of battery and energy storage technology has the current version, so check there before you rely on a summary.
What to check once you have a battery bank size
Once you know your target Ah and weight, run the system weight and portability calculator for a full system weight picture, including panels and other equipment beyond just the batteries. The battery lifespan estimator in our maintenance and lifespan tools projects how many years this bank should last under typical RV use, and DOE's overview of battery and energy storage technology is a good next read if any of the terminology here is new.