Lithium vs AGM: which costs less over the life of the battery?
A LiFePO4 battery costs more up front than AGM but usually less to own. You get about twice the usable capacity from the same amp-hour rating, so one 100Ah lithium battery does the work of two 100Ah AGM batteries, and it keeps doing it for many years longer. Compare batteries on cost per usable amp-hour per year, not sticker price. Expion360 LiFePO4 batteries carry a 12-year warranty.
What does each battery actually give you?
| Expion360 LiFePO4, 12V 100Ah | AGM lead-acid, 12V 100Ah | |
|---|---|---|
| Usable capacity | ~100Ah | ~50Ah |
| Batteries needed for 100Ah usable | 1 | 2 |
| Weight for 100Ah usable | 29 lb | 120–140 lb (two batteries) |
| Charge rate | Up to 0.5C | 0.2–0.3C |
| Voltage under load | Flat | Sags as it discharges |
| Service life | Roughly 10× standard lead-acid, per Expion360 guidance | Baseline |
| Warranty | 12 years | Varies by brand |
| Maintenance | None | None (sealed) |
AGM figures are typical for the class. Actual life depends on temperature, charge and discharge rates and storage.
How do you compare the real cost of two batteries?
| Step | What to do |
|---|---|
| 1 | Take the price of enough batteries to give the usable capacity you need |
| 2 | Divide by the usable amp-hours (about 100% of rating for LiFePO4, about 50% for AGM) |
| 3 | Divide again by the years of service you expect — the warranty term is the safest number to use |
| 4 | Add replacements, extra charging time and any fuel or generator hours the weaker battery costs you |
| 5 | Compare the results: cost per usable amp-hour per year |
Why does AGM give only half its rated capacity?
Lead-acid batteries age much faster when they are routinely drained deep, so the usual guidance is to stop at about 50% state of charge. A 100Ah AGM battery therefore gives you around 50Ah you can actually use. LiFePO4 is rated for deep discharge, so a 100Ah Expion360 battery delivers close to its full 100Ah.
Is lithium worth the higher up-front price?
For most RV, van and boat owners who use their batteries regularly, yes. Count everything AGM costs over the same period: a second battery to match the usable capacity, replacements as it wears out, longer generator or engine run time because it charges more slowly, and the weight you haul around. A battery covered for 12 years spreads its price over far more years of service.
When does AGM still make sense?
When the battery is rarely used and only lightly discharged, such as a weekend trailer that sits plugged in, or as an engine starting battery. AGM also tolerates charging below freezing at a reduced rate, which an unheated LiFePO4 battery does not; Expion360's VHC™ heated models close that gap by warming their cells before charging.
Does lithium save money on charging?
It saves time, which often means fuel. LiFePO4 accepts charge at up to 0.5C on Expion360 batteries, against roughly 0.2–0.3C for AGM, and it doesn't need a long absorption phase to top off. That means fewer generator hours and more of each day's solar actually stored.