LiFePO4 (lithium iron phosphate) and lead-acid batteries store the same thing, but they behave very differently in service. This guide compares them on the six factors that actually change your bill: cycle life, usable capacity, weight, efficiency, safety and total cost of ownership.
Quick answer: which should you buy?
Choose LiFePO4 if the battery cycles daily, if weight matters, if you need deep discharges, or if you can amortise a higher upfront cost over 8–10 years. Choose lead-acid only for low-cycle standby duty (a few discharges per year) where the cheapest upfront price wins, and where weight and depth of discharge are irrelevant.
Side-by-side comparison
| Factor | LiFePO4 | Sealed lead-acid (AGM/GEL) |
|---|---|---|
| Cycle life (to 80% capacity) | 3,000–6,000+ cycles | 300–800 cycles |
| Recommended depth of discharge | 80–90% | 50% (max) |
| Usable energy from a 100Ah unit | ~1.1–1.2kWh (12V) | ~0.6kWh (12V) |
| Round-trip efficiency | 95–98% | 80–85% |
| Weight (12V 100Ah) | ~10–13kg | ~25–32kg |
| Voltage behaviour under load | Flat until nearly empty | Sags continuously |
| Maintenance | None | Periodic checks, terminal cleaning |
| Typical service life | 10+ years | 3–5 years |
| Charging speed | 0.5C–1C typical | 0.1C–0.2C typical |
| Upfront cost | Higher | Lower |
1. Cycle life: the single biggest difference
A cycle is one full charge and discharge. A quality LiFePO4 pack rated at 6,000 cycles to 80% depth of discharge will still be usable after well over a decade of daily cycling. A good AGM battery cycled to 50% depth of discharge typically delivers 500–800 cycles, which is about two to three years of daily use.
The practical consequence: in a solar home that cycles every day, you will replace lead-acid three to five times in the period one LiFePO4 pack is still in service.
2. Usable capacity: the spec sheet is misleading
Both batteries may be sold as "12V 100Ah", but you cannot use the same amount of energy from them. Discharging lead-acid below 50% state of charge causes permanent sulphation damage, so a 100Ah lead-acid battery realistically gives you about 50Ah. LiFePO4 is routinely discharged to 80–90%, so the same nominal rating yields roughly 85–90Ah.
3. Weight and space
LiFePO4 has roughly three to four times the energy density of lead-acid by weight. In golf carts and RVs this is transformative: a golf cart losing 100–150kg of battery mass accelerates better, climbs hills with less voltage sag, and reduces wear on tyres, brakes and suspension. In marine applications, removing weight from the bilge improves stability.
4. Charging efficiency and speed
Lead-acid loses 15–20% of the energy you push into it as heat, and its absorption stage is slow — the last 20% of charge can take hours. LiFePO4 accepts charge at 95–98% efficiency and can typically take 0.5C to 1C, meaning a 100Ah pack can be recharged in roughly one to two hours instead of eight to ten. For solar systems this means more of your panel output is actually stored, particularly on short winter days.
5. Safety and temperature
LiFePO4 is the most thermally stable of the common lithium chemistries. Its olivine phosphate structure does not release oxygen under thermal stress the way cobalt-based lithium cells can, so the thermal runaway risk is far lower. Operating windows are wide: STORASTRA ENERGY packs are specified for discharge from -20°C to 55°C and charge from 0°C to 55°C.
The one hard limit to respect: you must not charge a standard LiFePO4 pack below 0°C unless it has a low-temperature charge cut-off or self-heating function. A Battery Management System handles this automatically.
6. Total cost of ownership
Lead-acid wins on sticker price and loses on cost per delivered kilowatt-hour. A worked example over ten years for a system cycling once per day:
- Lead-acid: buy a bank, replace it roughly three to four times, absorb 15–20% charging losses, and dispose of the scrap.
- LiFePO4: buy one pack, no replacements inside the horizon, minimal losses, and a residual value at the end.
Across a decade of daily cycling, lithium is commonly the cheaper option per usable kWh — the crossover point is usually reached between year three and year five. If the battery cycles fewer than about 30 times a year, lead-acid can still come out ahead.
When lead-acid is still the right call
- Emergency standby with fewer than ~20–30 discharges per year.
- Very tight capital budgets with no visibility on long-term operating cost.
- Extremely cold unheated sites without a low-temperature charging solution.
- Cranking batteries for engine starting, where the burst current requirement and duty cycle suit lead-acid.
What you must change when switching to LiFePO4
- Charger or solar controller — must have a LiFePO4 profile (14.2–14.6V absorption for 12V, no equalisation, no desulphation pulse).
- Inverter low-voltage cut-off — set for lithium voltages, since lithium holds voltage and then drops quickly at the end.
- Alternator or generator charging — a DC-DC charger is usually needed to limit current and protect the alternator.
- Cable and fuse sizing — lithium can deliver far higher current; protection must be sized for the pack, not the old bank.
If you would rather not work through that list yourself, our team specifies the full conversion — see the 12V LiFePO4 battery and golf cart LiFePO4 battery pages, or send us your system details on the contact page.
FAQ
For anything that cycles daily — solar storage, golf carts, RV house banks — yes. Lithium commonly becomes cheaper per usable kWh within three to five years, because it needs no replacement and wastes far less energy during charging.
Usually no. Lead-acid chargers apply an equalisation or desulphation voltage that a LiFePO4 BMS will reject, and they often lack a proper lithium absorption profile. A lithium-compatible charger is a required part of the conversion.
Because lead-acid should only be discharged to about 50% while LiFePO4 can go to 80–90%, a 100Ah LiFePO4 battery typically replaces roughly 180–200Ah of lead-acid.