House battery

The house battery is the power source behind everything in the living area that isn't plugged into shore power: interior lights, the water pump, roof fans, the furnace fan, and any 12V outlets. It is wired separately from the chassis starting battery so that running the lights all evening won't leave you unable to start the engine or tow vehicle in the morning.

Most rigs come with one or two lead-acid or AGM batteries wired in parallel, but many owners upgrade to a single larger lithium (LiFePO4) battery for more usable capacity in a similar footprint. The right size depends on how much you use without shore power, what you run overnight, and whether you plan to boondock regularly or mostly stay at campgrounds with hookups.

The most common mistake is buying based on price or brand alone without checking amp-hour capacity against actual power draw, or mixing battery chemistries and ages in the same bank. A battery monitor, rather than the dash voltage gauge, is the only reliable way to know how much usable capacity is really left.