LiFePO4 vs lithium-ion vs AGM: which battery is best for an RV or boat?
For house power in an RV, van or boat, LiFePO4 (lithium iron phosphate) is the right choice. It is the most thermally stable lithium chemistry, delivers nearly its full rated capacity, weighs about half as much as AGM and recharges up to three times faster. Other lithium-ion chemistries pack more energy per pound but are less stable, which is why they are used in phones and EVs rather than house batteries. Expion360 batteries are LiFePO4 with a 12-year warranty.
How do LiFePO4, other lithium-ion and AGM batteries compare?
LiFePO4 trades a little energy density for a lot of stability and cycle life, which is the right trade for a battery that lives in a compartment under your bed. AGM is cheap and familiar but heavy and half-usable. NMC and other lithium-ion chemistries are reserved for applications where weight is everything.
| LiFePO4 (Expion360) | Other lithium-ion (NMC / NCA) | AGM lead-acid | |
|---|---|---|---|
| Usable capacity from 100Ah | ~100Ah | ~90Ah | ~50Ah |
| Weight, 100Ah 12V | 29 lb | Lighter | 60–70 lb |
| Thermal stability | Highest of the lithium chemistries | Lower; requires more protection | Stable |
| Nominal voltage | 12.8V | 14.4–14.8V | 12.0V |
| Charge rate | Up to 1P | Varies | 0.2–0.3C |
| Voltage under load | Flat | Flat | Sags |
| Maintenance | None | None | None (sealed) |
| Typical use | RV, marine, off-grid house power | Phones, EVs, power tools | Starting batteries, budget house banks |
| Warranty | 12 years (Expion360) | Varies | Varies |
AGM and NMC figures are typical for the class.
What is the difference between LiFePO4 and lithium-ion?
LiFePO4 is one type of lithium-ion battery. 'Lithium-ion' is the family; lithium iron phosphate, NMC (nickel manganese cobalt) and NCA are members of it. LiFePO4 uses an iron-phosphate cathode that is chemically and thermally stable, so it tolerates abuse, heat and deep discharge far better than cobalt-based chemistries. The cost is lower energy density — a LiFePO4 pack is a bit bigger and heavier for the same watt-hours.
For house power the trade is easy: a few extra pounds in a compartment does not matter, and stability does. That is why nearly every reputable RV and marine lithium battery, including every Expion360 battery, is LiFePO4.
Is LiFePO4 safer than other lithium batteries?
Yes. The iron-phosphate cathode does not release oxygen when it overheats, so the thermal runaway that makes cobalt-based cells dangerous is far harder to trigger. Combine that with a BMS that guards against over-charge, over-discharge, short circuit and over-temperature, UL1642-recognized steel-encased cells and a UL1973 listing on the finished battery, and LiFePO4 is the chemistry to put in a living space.
Why is LiFePO4 better than AGM for house power?
Usable capacity, weight and voltage. An AGM battery should not be discharged below 50%, so a 100Ah AGM gives you about 50Ah; LiFePO4 gives you nearly all 100Ah. LiFePO4 weighs about half as much. And LiFePO4 holds 12.8–13.2V until it is almost empty, where AGM sags as it drains and starves fridges and furnace fans. AGM's only advantages are up-front price and that it tolerates charging below freezing.
Expion360 closes the cold-weather gap with VHC™ heated models that warm their own cells and charge down to -4°F (-20°C).
You dry camp, run a 12V fridge or inverter, care about weight, or want the bank to last.
It's a starting battery, or a rarely used trailer on shore power where price is the only concern.
Can I replace AGM with LiFePO4 in my existing system?
Usually yes, with two checks. The charger, converter and alternator path must have a LiFePO4 charge profile — lead-acid profiles undercharge lithium or trip the BMS. And the battery has to fit: Expion360 Group 24 and Group 27 batteries use the same footprints as their lead-acid equivalents, and the GC2 replaces a pair of 6V golf-cart batteries. Never mix lithium and lead-acid in one bank.
How long does a LiFePO4 battery last compared with AGM?
In laboratory testing, LiFePO4 batteries deliver thousands of cycles whereas AGM batteries yield only hundreds. Because actual cycle counts are hard for buyers to verify, the most reliable point of comparison is the warranty. Every Expion360 house battery features an industry-leading 12-year warranty, providing a clear, time-based guarantee rather than a hard-to-verify cycle count.