LiFePO4 vs Lead-Acid
Both store DC energy, but they behave nothing alike over a project's life. Here is the comparison that matters for a specifier.
Cycle life and depth of discharge
- Lead-acid (VRLA): 300–1,200 cycles, and you should only use ~50% of capacity or life collapses.
- LiFePO4: 2,000–6,000 cycles at 80–90% depth of discharge.
Usable energy
A 100 Ah lead-acid bank gives you ~50 Ah usable. A 100 Ah LiFePO4 gives you ~90 Ah. Same nameplate, ~80% more usable energy.
Efficiency and maintenance
LiFePO4 round-trip efficiency is ~95% vs ~80% for lead-acid, so you lose less to charging. Lead-acid needs equalisation, venting and periodic replacement; LiFePO4 is sealed and maintenance-free behind a BMS.
Upfront vs total cost
Lead-acid wins on first price. Over 5–10 years, LiFePO4 usually wins on total cost because it is replaced far less often and delivers more usable cycles. The VRLA-to-LiFePO4 retrofit checklist walks through the switch.
When lead-acid still fits
Very small, rarely cycled, budget-only backup where weight and life are not concerns. For anything cycled daily or space-constrained, LiFePO4.