LiFePO4 (lithium iron phosphate) batteries deliver more usable energy per amp-hour than any lead-acid type. This calculator uses LiFePO4-specific defaults for depth of discharge and efficiency, giving you a realistic runtime estimate without the guesswork.
LiFePO4 vs Other Battery Chemistries
| Specification | LiFePO4 | AGM Lead-Acid | Flooded Lead-Acid | Lithium-Ion (NMC) |
|---|---|---|---|---|
| Usable DoD | 80-100% | 50% | 50% | 80-90% |
| Cycle Life | 2,000-5,000 | 300-500 | 300-700 | 500-1,000 |
| Round-trip Efficiency | 92-98% | 80-85% | 75-85% | 85-95% |
| Weight per kWh | ~7 kg | ~25 kg | ~30 kg | ~6 kg |
| Self-discharge/month | 2-3% | 3-5% | 5-15% | 3-5% |
| Thermal Runaway Risk | Very low | None (but gassing risk) | None (but gassing risk) | Moderate |
The usable capacity gap is the key difference. A 100Ah LiFePO4 battery at 80% DoD delivers 80Ah of usable power. A 100Ah AGM at its safe 50% DoD delivers just 50Ah — 37.5% less usable energy from the same amp-hour rating.
The LiFePO4 Voltage Curve Advantage
LiFePO4 cells hold a remarkably flat voltage throughout discharge. A single cell stays between 3.2V and 3.3V from 10% to 90% state of charge. This flat curve means your 12V system delivers nearly constant power whether the battery is nearly full or nearly empty.
Compare that to lead-acid, where a 12V battery drops from 12.7V at full to 11.8V at 50% discharge. That voltage sag reduces the effective wattage available to your devices and makes some sensitive electronics behave erratically.
The practical impact: a LiFePO4-powered inverter maintains consistent AC output right up until the BMS cuts off, while a lead-acid system gradually loses capacity as voltage drops. For devices with minimum voltage requirements — like 12V compressor fridges — LiFePO4 delivers noticeably longer effective runtimes than the raw numbers suggest.
Frequently Asked Questions
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LiFePO4 dominates the off-grid and mobile power space for good reason. Higher usable capacity, longer cycle life, and flat voltage output make it the best chemistry for most applications — provided you can handle the upfront cost. Run your numbers above, then check whether the cost-per-cycle math works for your use case.
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Written and maintained by Dan Dadovic, Developer & Off-Grid Energy Enthusiast. On the energy side, Dan has hands-on experience with residential solar panel installation, DIY battery bank construction, off-grid power systems, and wind power — all from building and maintaining his own systems..
Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.