How does a LiFePO₄ battery perform in the cold?

SOLiCORE retains more than 97% of discharge capacity at −20 °C, genuinely strong low-temperature discharge performance, and better than lead-acid, which loses substantial capacity as temperature falls. The discharge range is −20 °C to 60 °C.

But charging is the constraint, and it is a real one rather than a marketing caveat. SOLiCORE’s charge temperature range is 0 °C to 55 °C, and LiFePO₄ must not be charged below 0 °C. Below freezing, lithium ions cannot intercalate into the graphite anode fast enough and instead plate onto it as metallic lithium, permanently raising internal resistance, reducing capacity, and potentially forming dendrites that create internal shorts. The damage is cumulative and irreversible. The integrated battery management system enforces the charge temperature limit.

Sub-zero mornings are routine in the Snowy Monaro, the Central and Southern Tablelands, alpine rail corridors, Armidale, Ballarat and much of the inland in winter. In New Zealand, the same applies across alpine regions, the Central Plateau, and much of the South Island. It is not a theoretical concern.

Australian and New Zealand road authorities have engineered explicitly around it. TMR’s MRTS213 requires roadside cabinets to hold a minimum internal temperature of 0 °C with a thermostatically controlled heater. NZTA’s ITS specification requires backup times to be met at 0 °C. Both standards treat sub-zero operation as a baseline design requirement, not an edge case.

The mitigations are straightforward once the problem is acknowledged: an insulated enclosure with a thermostatic heater, or siting inside a conditioned space. What is not acceptable is a design that assumes the battery will charge on a July morning in Cooma because the datasheet says −20 °C.

Note also the storage range: −20 °C to 45 °C. A battery stored in an uninsulated shed through a Pilbara summer is being aged before it is ever commissioned.