Short answer: LiFePO4 gives about twice the usable energy per amp-hour, weighs much less and lasts many more cycles, but costs more up front and needs cold-charging protection. AGM is cheaper to buy and tolerates charging in the cold, but should only be used to about 50%.
| Criteria | LiFePO4 | AGM |
|---|---|---|
| Usable capacity | ~80–100% of rating | ~50% for long life |
| Weight | Much lighter for the same usable energy | Heavy |
| Cycle life | Typically thousands of cycles (see maker's rating) | Typically hundreds at 50% depth |
| Voltage under load | Stays flat (~13 V) | Sags as it discharges |
| Charging in freezing temps | Blocked/needs heating | Allowed (slower) |
| Charger profile | Needs lithium profile | Standard AGM profile |
| Up-front cost | Higher | Lower |
More: RV lithium battery buying guide · cost per Wh calculator · charging lithium in the cold.
Safety: These are general estimates, not a design. Follow your equipment manufacturer's instructions and local electrical code, and consult a qualified electrician for anything connected to shore power, a house, or high-current batteries.
For frequent boondocking, usually yes: more usable energy, less weight and longer life often outweigh the higher price. For occasional hookup camping, AGM can be enough.
Often, but check the converter/charger, solar controller and alternator charging for lithium compatibility.
Roughly two 100Ah AGMs give similar usable energy to one 100Ah LiFePO4, because AGM is typically only used to about 50%.
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