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Smart Lock Battery Chemistries

Updated October 11, 2026

The three chemistries

Alkaline (AA)

Cheapest per pack, worst in cold and under Wi-Fi load. Fine for Bluetooth keypad locks on sheltered doors. Replace on schedule, not on low-battery beep.

Lithium AA (disposable)

Holds voltage in freezing weather and under pulse loads. The right choice for exposed doors and Wi-Fi locks in cold climates. Costs more per cell, fewer changes per year.

Rechargeable (NiMH / lithium-ion packs)

Lowest yearly cost for high-traffic doors. NiMH self-discharges faster in cold; built-in packs (some Yale, Eufy) charge over USB. Model the tradeoff in the battery estimator and price it in the cost estimator.

Rules that beat chemistry

• Change all cells at once; never mix old and new.
• Cold doors get lithium, always.
• Keep one spare set where you can reach it without the lock — garage, car, neighbor.
• Log install dates; locks die at 2 a.m. in January.