Smart Lock Battery Life Estimator
Estimate how long your smart lock's batteries will last based on daily usage, lock model power consumption, and battery capacity.
Typical AA alkaline ≈ 2500–3000 mAh; AA lithium ≈ 3000–3500 mAh
Most smart locks use 4 AA batteries
Each entry + exit counts as 2 cycles
Typical smart lock motor: 300–800 mA during actuation
Time motor runs per lock/unlock cycle (typically 1–3 s)
BLE/Zigbee idle draw: 0.1–2 mA; Wi-Fi locks: 5–20 mA
Current during BLE/Wi-Fi handshake per cycle (BLE ≈ 10–20 mA, Wi-Fi ≈ 50–150 mA)
Duration of RF activity per lock/unlock event
Accounts for temperature, Peukert effect, and end-of-life voltage cutoff (typically 70–85%)
Fill in the fields above and click Calculate.
Formula
Usable Capacity (mAh) = Capacity per Cell × (Efficiency / 100)
Motor mAh/day = Imotor (mA) × tactuation (s) ÷ 3600 × Cycles/day
RF mAh/day = IRF (mA) × tRF (s) ÷ 3600 × Cycles/day
Standby mAh/day = Istandby (mA) × 24 h
Total Daily Consumption = Motor mAh/day + RF mAh/day + Standby mAh/day
Battery Life (days) = Usable Capacity ÷ Total Daily Consumption
Note: For series battery packs (standard in smart locks), pack capacity equals single-cell capacity. Parallel configurations would multiply capacity by cell count.
Assumptions & References
- AA alkaline batteries (e.g., Energizer, Duracell) provide approximately 2,500–3,000 mAh at low drain rates (IEC 60086 standard).
- AA lithium batteries (e.g., Energizer Ultimate) provide approximately 3,000–3,500 mAh and perform better in cold temperatures.
- The efficiency/derating factor (70–85%) accounts for the Peukert effect (capacity reduction at high current), temperature losses, and the lock's minimum operating voltage cutoff (~0.9–1.0 V/cell).
- Motor current during actuation: 300–800 mA is typical for DC gear motors used in smart locks (Schlage, Yale, August specifications).
- BLE (Bluetooth Low Energy) idle current: 0.1–2 mA; active communication: 10–20 mA (Bluetooth SIG Core Spec 5.0).
- Wi-Fi module idle current: 5–20 mA; active TX/RX: 50–150 mA (ESP32 datasheet, Nordic nRF52 datasheet).
- Zigbee/Z-Wave idle: 0.5–5 mA; active: 15–30 mA.
- Average household door usage: 8–15 lock/unlock cycles per day (U.S. DOE residential energy studies).
- Manufacturer-claimed battery life (e.g., August Smart Lock: 3–6 months, Schlage Encode: 6 months) aligns with these calculations at typical usage levels.
- This estimator assumes constant temperature (~20°C / 68°F). Cold environments (<0°C) can reduce effective capacity by 20–50%.