LiFePO4 vs AGM for an RV House Battery: Which One to Buy

For a boondocker, usually yes. For a campground camper who plugs in most nights, often no. The honest way to compare is dollars per usable amp-hour, not dollars per rated amp-hour. A 100Ah AGM at roughly $270 gives about 50Ah usable, near $5.40 per usable amp-hour. A 100Ah LiFePO4 at roughly $160 gives about 80Ah usable, near $2 per usable amp-hour, before counting that it also survives several times more cycles. The AGM is cheaper on the shelf and more expensive per amp-hour you can actually draw.

Usable depth of discharge figures below are a convention, not a manufacturer specification. Manufacturers publish cycle life against a depth of discharge curve rather than a single usable number, and the values here are the widely used planning assumption for each chemistry.

A lithium bank is not a drop-in replacement in the way it is marketed. It needs a genuine lithium charge profile at every source that touches it: the converter, the solar charge controller and any DC-DC charger from the alternator. A converter or controller running a lead-acid profile will undercharge a lithium bank and never reach full capacity. Check every charging source before you buy the battery, not after.

The other real limitation is cold weather. A LiFePO4 cell must not accept charge current below freezing without a low-temperature BMS cutoff, or with a self-heating pack like the Redodo above. Charging a standard LiFePO4 battery below freezing degrades the cells even when the BMS lets current through on some designs, so check that the specific battery's BMS actually stops charging at low temperature rather than assuming it.

A weekend camper who plugs into shore power most nights and rarely dry camps past a day or two will not draw down the bank far enough, or often enough, for the lithium cycle-life advantage to pay back the price difference. A rig that already has a lead-acid converter, with no plan to replace it, avoids the charge-profile problem entirely by staying on AGM. And a backup or seasonal-storage battery that sits mostly idle has no cycle count to amortize a lithium premium against.

A 100Ah AGM battery at roughly 60 to 65 pounds versus a 100Ah LiFePO4 battery at roughly 22 to 26 pounds is not just a lifting convenience, it is payload. A two or three battery lead-acid bank can eat 150 to 200 pounds of a trailer's cargo carrying capacity before a single pot, tool or gallon of water goes in. Owners who are already tight on payload, which is common on smaller travel trailers with modest CCC ratings, often find the weight savings alone worth more than the cycle-life argument, independent of how they camp.

Most LiFePO4 packs in this catalog ship with a built-in battery management system that protects against over-discharge, over-current and, on the models above, over-temperature and low-temperature charging. That BMS will disconnect the battery rather than let it be damaged, which shows up as the battery simply cutting out under a fault rather than failing gradually. A standard AGM battery has no equivalent internal protection: it will accept an over-discharge or a wiring fault without disconnecting itself, and the failure shows up later as reduced capacity or a swollen case rather than an immediate, protective cutoff.

A LiFePO4 battery holds a flat voltage across most of its discharge curve, only dropping sharply near the bottom of its usable range, which means a simple voltage-based meter reads misleadingly close to full right up until the battery is nearly empty. An AGM battery's voltage drops more steadily and predictably as it discharges, so a basic voltmeter gives a rougher but more continuously useful state of charge estimate on lead-acid than it does on lithium. This is the practical reason a shunt-based battery monitor, which tracks amp-hours in and out rather than voltage alone, is treated as close to mandatory on a LiFePO4 bank and optional on an AGM one.

Match the battery to how you actually camp, not to the marketing on the box. A weekend camper who plugs into shore power most nights gets little benefit from lithium cycle life. A boondocker running a fridge and a CPAP off the battery for a week between charges gets the usable-capacity gap back within a season or two.