Smart Lock Battery Life Estimator
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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.
Battery Capacity (mAh per cell)
Typical AA alkaline ≈ 2500–3000 mAh; AA lithium ≈ 3000–3500 mAh
Number of Battery Cells
Most smart locks use 4 AA batteries
Lock/Unlock Cycles per Day
Each entry + exit counts as 2 cycles
Motor Current Draw (mA)
Typical smart lock motor: 300–800 mA during actuation
Actuation Time per Cycle (seconds)
Time motor runs per lock/unlock cycle (typically 1–3 s)
Standby / Idle Current Draw (mA)
BLE/Zigbee idle draw: 0.1–2 mA; Wi-Fi locks: 5–20 mA
RF / Communication Current Draw (mA)
Current during BLE/Wi-Fi handshake per cycle (BLE ≈ 10–20 mA, Wi-Fi ≈ 50–150 mA)
RF Communication Duration per Cycle (seconds)
Duration of RF activity per lock/unlock event
Battery Efficiency / Derating Factor (%)
Accounts for temperature, Peukert effect, and end-of-life voltage cutoff (typically 70–85%)
Estimate Battery Life Fill in the fields above and click Calculate.
function smaCalc() { var resultEl = document.getElementById('sma-result');
// --- Read inputs --- var capacityPerCell = parseFloat(document.getElementById('sma-battery-capacity').value); var numCells = parseFloat(document.getElementById('sma-num-cells').value); var cyclesPerDay = parseFloat(document.getElementById('sma-lock-unlocks').value); var motorCurrent = parseFloat(document.getElementById('sma-motor-current').value); var actuationTime = parseFloat(document.getElementById('sma-actuation-time').value); var standbyCurrent = parseFloat(document.getElementById('sma-standby-current').value); var rfCurrent = parseFloat(document.getElementById('sma-rf-current').value); var rfDuration = parseFloat(document.getElementById('sma-rf-duration').value); var efficiency = parseFloat(document.getElementById('sma-efficiency').value);
// --- Validation --- var errors = []; if (isNaN(capacityPerCell) || capacityPerCell 10000) errors.push("Battery capacity must be between 100 and 10,000 mAh."); if (isNaN(numCells) || numCells 12 || !Number.isInteger(numCells)) errors.push("Number of cells must be a whole number between 1 and 12."); if (isNaN(cyclesPerDay) || cyclesPerDay 500) errors.push("Lock/unlock cycles per day must be between 1 and 500."); if (isNaN(motorCurrent) || motorCurrent 2000) errors.push("Motor current must be between 50 and 2,000 mA."); if (isNaN(actuationTime) || actuationTime 10) errors.push("Actuation time must be between 0.5 and 10 seconds."); if (isNaN(standbyCurrent) || standbyCurrent 50) errors.push("Standby current must be between 0.01 and 50 mA."); if (isNaN(rfCurrent) || rfCurrent 200) errors.push("RF current must be between 0 and 200 mA."); if (isNaN(rfDuration) || rfDuration 30) errors.push("RF duration must be between 0.1 and 30 seconds."); if (isNaN(efficiency) || efficiency 100) errors.push("Efficiency must be between 50% and 100%.");
if (errors.length > 0) { resultEl.innerHTML = 'Please fix the following:' + errors.map(function(e){ return ''; }).join('') + ''; return; }
// --- Core Formula --- // Total usable capacity (mAh) — batteries in series share same capacity; // parallel cells multiply capacity. The calculator treats numCells as series (standard for smart locks). // Usable capacity = capacityPerCell * efficiency_factor var efficiencyFactor = efficiency / 100.0; var usableCapacity_mAh = capacityPerCell * efficiencyFactor; // mAh (series pack)
// Daily energy consumed (mAh/day): // Motor energy per day = motorCurrent (mA) * actuationTime (s) * cyclesPerDay / 3600 (s/h) // RF energy per day = rfCurrent (mA) * rfDuration (s) * cyclesPerDay / 3600 // Standby energy per day = standbyCurrent (mA) * 24 (h) var motorMah_day = motorCurrent * (actuationTime / 3600.0) * cyclesPerDay; var rfMah_day = rfCurrent * (rfDuration / 3600.0) * cyclesPerDay; var standbyMah_day = standbyCurrent * 24.0;
var totalMah_day = motorMah_day + rfMah_day + standbyMah_day;
// Battery life in days var batteryLifeDays = usableCapacity_mAh / totalMah_day; var batteryLifeMonths = batteryLifeDays / 30.44; var batteryLifeYears = batteryLifeDays / 365.25;
// Percentage breakdown var motorPct = (motorMah_day / totalMah_day * 100).toFixed(1); var rfPct = (rfMah_day / totalMah_day * 100).toFixed(1); var standbyPct = (standbyMah_day / totalMah_day * 100).toFixed(1);
// Format life output var lifeStr = ""; if (batteryLifeDays ' + '' + 'Component' + 'mAh/day' + 'Share' + 'Motor actuation' + '' + motorMah_day.toFixed(3) + '' + '' + motorPct + '%' + 'RF / Communication' + '' + rfMah_day.toFixed(3) + '' + '' + rfPct + '%' + 'Standby / Idle' + '' + standbyMah_day.toFixed(3) + '' + '' + standbyPct + '%' + 'Total' + '' + totalMah_day.toFixed(3) + '' + '100%' + '' + 'Usable capacity: ' + usableCapacity_mAh.toFixed(0) + ' mAh (per cell, after ' + efficiency + '% derating)' + 'Assessment: ' + rating; }
#### 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
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