What are the downsides of LiFePO4 batteries?

LiFePO4 batteries have four real downsides: higher upfront cost than lead-acid, a strict no-charging-below-32°F rule, lower energy density by volume, and the need for a LiFePO4-compatible charger — not your old lead-acid unit.

The cost gap is the most immediate friction: a 100Ah LiFePO4 pack runs roughly 2–3× more than a comparable AGM battery at purchase. The cold-charging restriction is the most damaging if ignored — charging LiFePO4 cells below freezing causes lithium plating, which permanently reduces capacity. Lower volumetric energy density means LiFePO4 packs are physically larger than NMC lithium alternatives at the same watt-hour rating, though they're still 67% lighter than lead-acid equivalents.

• LiFePO4 charging must stop at 32°F (0°C) — charging below that temperature permanently damages cells through lithium plating.
• LiFePO4 upfront cost is roughly 2–3× higher than AGM at equivalent Ah capacity.
• LiFePO4 energy density is lower than NMC lithium — roughly 90–120 Wh/kg vs. 150–220 Wh/kg for NMC.
• LiFePO4 batteries require a charger set to an LFP profile (14.4–14.6V absorption) — lead-acid charger profiles will undercharge or damage the pack.
• LiFePO4's flat discharge curve makes state-of-charge harder to read from voltage alone without a dedicated battery monitor.