74  IoT Formula Calculator

Interactive Calculator for Common IoT Calculations

74.1 IoT Formula Calculator

NoteQuick Calculations

Select a formula category and enter values to get instant results. All calculations include explanations and typical values.

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74.2 Select Calculation Type

viewof calculationType = Inputs.radio(
  ["Link Budget", "Battery Life", "ADC/Signal", "Data Rate", "Unit Converter"],
  {label: "Calculate:", value: "Link Budget"}
)

---

74.3 Calculator

linkBudgetCalc = {
  if (calculationType !== "Link Budget") return null;

  return html`
    <div style="background: linear-gradient(135deg, #E8F6F3 0%, #D5F4E6 100%); padding: 25px; border-radius: 12px;">
      <h3 style="margin-top: 0; color: #16A085;">Link Budget Calculator</h3>
      <p style="color: #666;">Calculate received signal strength and determine if a link is viable.</p>
    </div>
  `;
}

linkBudgetCalc

viewof txPowerDbm = calculationType === "Link Budget" ? Inputs.range([-10, 30], {
  label: "TX Power (dBm):",
  value: 14,
  step: 1
}) : null

viewof txAntennaGain = calculationType === "Link Budget" ? Inputs.range([0, 15], {
  label: "TX Antenna Gain (dBi):",
  value: 2,
  step: 0.5
}) : null

viewof rxAntennaGain = calculationType === "Link Budget" ? Inputs.range([0, 15], {
  label: "RX Antenna Gain (dBi):",
  value: 2,
  step: 0.5
}) : null

viewof distanceM = calculationType === "Link Budget" ? Inputs.range([1, 50000], {
  label: "Distance (meters):",
  value: 1000,
  step: 10
}) : null

viewof frequencyMhz = calculationType === "Link Budget" ? Inputs.range([100, 6000], {
  label: "Frequency (MHz):",
  value: 868,
  step: 1
}) : null

viewof rxSensitivity = calculationType === "Link Budget" ? Inputs.range([-150, -70], {
  label: "RX Sensitivity (dBm):",
  value: -120,
  step: 1
}) : null

linkBudgetResult = {
  if (calculationType !== "Link Budget") return null;

  const fspl = 20 * Math.log10(distanceM) + 20 * Math.log10(frequencyMhz * 1e6) - 147.55;
  const eirp = txPowerDbm + txAntennaGain;
  const rxPower = eirp - fspl + rxAntennaGain;
  const margin = rxPower - rxSensitivity;
  const linkWorks = margin > 0;

  return html`
    <div style="background: ${linkWorks ? '#D5F4E6' : '#FADBD8'}; padding: 20px; border-radius: 12px; margin: 20px 0;">
      <h4 style="margin-top: 0; color: ${linkWorks ? '#27AE60' : '#E74C3C'};">
        ${linkWorks ? 'Link is Viable' : 'Link Will Fail'}
      </h4>

      <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 15px;">
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">EIRP</div>
          <div style="font-size: 20px; font-weight: bold; color: #2C3E50;">${eirp.toFixed(1)} dBm</div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Path Loss</div>
          <div style="font-size: 20px; font-weight: bold; color: #E74C3C;">${fspl.toFixed(1)} dB</div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">RX Power</div>
          <div style="font-size: 20px; font-weight: bold; color: #3498DB;">${rxPower.toFixed(1)} dBm</div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Link Margin</div>
          <div style="font-size: 20px; font-weight: bold; color: ${margin > 10 ? '#27AE60' : margin > 0 ? '#F39C12' : '#E74C3C'};">
            ${margin.toFixed(1)} dB
          </div>
        </div>
      </div>

      <div style="margin-top: 15px; padding: 10px; background: white; border-radius: 6px; font-size: 13px;">
        <strong>Calculation:</strong><br>
        FSPL = 20×log(${distanceM}) + 20×log(${frequencyMhz}×10⁶) - 147.55 = ${fspl.toFixed(1)} dB<br>
        RX Power = ${txPowerDbm} + ${txAntennaGain} - ${fspl.toFixed(1)} + ${rxAntennaGain} = ${rxPower.toFixed(1)} dBm<br>
        Margin = ${rxPower.toFixed(1)} - (${rxSensitivity}) = ${margin.toFixed(1)} dB
      </div>
    </div>
  `;
}

linkBudgetResult

batteryLifeCalc = {
  if (calculationType !== "Battery Life") return null;

  return html`
    <div style="background: linear-gradient(135deg, #FEF5E7 0%, #FCF3CF 100%); padding: 25px; border-radius: 12px;">
      <h3 style="margin-top: 0; color: #E67E22;">Battery Life Calculator</h3>
      <p style="color: #666;">Estimate how long your IoT device will run on battery power.</p>
    </div>
  `;
}

batteryLifeCalc

viewof batteryCapacity = calculationType === "Battery Life" ? Inputs.range([50, 10000], {
  label: "Battery Capacity (mAh):",
  value: 2000,
  step: 50
}) : null

viewof activeCurrent = calculationType === "Battery Life" ? Inputs.range([0.1, 500], {
  label: "Active Current (mA):",
  value: 80,
  step: 0.1
}) : null

viewof sleepCurrent = calculationType === "Battery Life" ? Inputs.range([0.001, 10], {
  label: "Sleep Current (mA):",
  value: 0.01,
  step: 0.001
}) : null

viewof activeTimePercent = calculationType === "Battery Life" ? Inputs.range([0.01, 100], {
  label: "Active Time (%):",
  value: 1,
  step: 0.01
}) : null

viewof batteryEfficiency = calculationType === "Battery Life" ? Inputs.range([50, 100], {
  label: "Usable Capacity (%):",
  value: 80,
  step: 5
}) : null

batteryResult = {
  if (calculationType !== "Battery Life") return null;

  const avgCurrent = (activeCurrent * activeTimePercent / 100) + (sleepCurrent * (100 - activeTimePercent) / 100);
  const effectiveCapacity = batteryCapacity * batteryEfficiency / 100;
  const lifeHours = effectiveCapacity / avgCurrent;
  const lifeDays = lifeHours / 24;
  const lifeMonths = lifeDays / 30;
  const lifeYears = lifeDays / 365;

  let lifeDisplay, lifeUnit;
  if (lifeYears >= 1) {
    lifeDisplay = lifeYears.toFixed(1);
    lifeUnit = "years";
  } else if (lifeMonths >= 1) {
    lifeDisplay = lifeMonths.toFixed(1);
    lifeUnit = "months";
  } else if (lifeDays >= 1) {
    lifeDisplay = lifeDays.toFixed(1);
    lifeUnit = "days";
  } else {
    lifeDisplay = lifeHours.toFixed(1);
    lifeUnit = "hours";
  }

  return html`
    <div style="background: #D5F4E6; padding: 20px; border-radius: 12px; margin: 20px 0;">
      <h4 style="margin-top: 0; color: #27AE60;">Estimated Battery Life</h4>

      <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 15px;">
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Average Current</div>
          <div style="font-size: 20px; font-weight: bold; color: #2C3E50;">
            ${avgCurrent < 1 ? (avgCurrent * 1000).toFixed(1) + ' uA' : avgCurrent.toFixed(2) + ' mA'}
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Usable Capacity</div>
          <div style="font-size: 20px; font-weight: bold; color: #E67E22;">${effectiveCapacity.toFixed(0)} mAh</div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Battery Life</div>
          <div style="font-size: 24px; font-weight: bold; color: #27AE60;">${lifeDisplay} ${lifeUnit}</div>
        </div>
      </div>

      <div style="margin-top: 15px; padding: 10px; background: white; border-radius: 6px; font-size: 13px;">
        <strong>Calculation:</strong><br>
        Avg Current = (${activeCurrent} × ${activeTimePercent}%) + (${sleepCurrent} × ${100-activeTimePercent}%) = ${avgCurrent.toFixed(4)} mA<br>
        Life = ${effectiveCapacity} mAh ÷ ${avgCurrent.toFixed(4)} mA = ${lifeHours.toFixed(0)} hours = ${lifeDays.toFixed(1)} days
      </div>
    </div>
  `;
}

batteryResult

adcCalc = {
  if (calculationType !== "ADC/Signal") return null;

  return html`
    <div style="background: linear-gradient(135deg, #E8F4FD 0%, #D4E6F1 100%); padding: 25px; border-radius: 12px;">
      <h3 style="margin-top: 0; color: #3498DB;">ADC & Signal Calculator</h3>
      <p style="color: #666;">Calculate ADC resolution, quantization error, and sampling requirements.</p>
    </div>
  `;
}

adcCalc

viewof adcBitsCalc = calculationType === "ADC/Signal" ? Inputs.range([8, 24], {
  label: "ADC Resolution (bits):",
  value: 12,
  step: 1
}) : null

viewof vrefCalc = calculationType === "ADC/Signal" ? Inputs.range([1.0, 5.0], {
  label: "Reference Voltage (V):",
  value: 3.3,
  step: 0.1
}) : null

viewof signalFreqCalc = calculationType === "ADC/Signal" ? Inputs.range([1, 100000], {
  label: "Max Signal Frequency (Hz):",
  value: 1000,
  step: 1
}) : null

adcResult = {
  if (calculationType !== "ADC/Signal") return null;

  const levels = Math.pow(2, adcBitsCalc);
  const stepSize = vrefCalc / levels;
  const stepSizeMv = stepSize * 1000;
  const quantError = stepSize / 2;
  const snrDb = 6.02 * adcBitsCalc + 1.76;
  const nyquistRate = signalFreqCalc * 2;
  const recommendedRate = signalFreqCalc * 5;

  return html`
    <div style="background: #D4E6F1; padding: 20px; border-radius: 12px; margin: 20px 0;">
      <h4 style="margin-top: 0; color: #3498DB;">ADC Specifications</h4>

      <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 15px;">
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Quantization Levels</div>
          <div style="font-size: 20px; font-weight: bold; color: #2C3E50;">${levels.toLocaleString()}</div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Step Size (LSB)</div>
          <div style="font-size: 20px; font-weight: bold; color: #E67E22;">
            ${stepSizeMv < 1 ? (stepSizeMv * 1000).toFixed(1) + ' uV' : stepSizeMv.toFixed(2) + ' mV'}
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Max Quant Error</div>
          <div style="font-size: 20px; font-weight: bold; color: #E74C3C;">
            +/-${(quantError * 1000).toFixed(2)} mV
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Theoretical SNR</div>
          <div style="font-size: 20px; font-weight: bold; color: #9B59B6;">${snrDb.toFixed(1)} dB</div>
        </div>
      </div>

      <div style="margin-top: 15px; padding: 10px; background: white; border-radius: 6px; font-size: 13px;">
        <strong>Sampling Requirements for ${signalFreqCalc} Hz signal:</strong><br>
        Nyquist minimum: ${nyquistRate.toLocaleString()} Hz<br>
        Recommended (5x): ${recommendedRate.toLocaleString()} Hz
      </div>
    </div>
  `;
}

adcResult

dataRateCalc = {
  if (calculationType !== "Data Rate") return null;

  return html`
    <div style="background: linear-gradient(135deg, #F5EEF8 0%, #E8DAEF 100%); padding: 25px; border-radius: 12px;">
      <h3 style="margin-top: 0; color: #9B59B6;">Data Rate Calculator</h3>
      <p style="color: #666;">Calculate bandwidth requirements for your IoT data stream.</p>
    </div>
  `;
}

dataRateCalc

viewof sensorCount = calculationType === "Data Rate" ? Inputs.range([1, 100], {
  label: "Number of Sensors:",
  value: 10,
  step: 1
}) : null

viewof bytesPerReading = calculationType === "Data Rate" ? Inputs.range([1, 100], {
  label: "Bytes per Reading:",
  value: 4,
  step: 1
}) : null

viewof readingsPerSecond = calculationType === "Data Rate" ? Inputs.range([0.001, 1000], {
  label: "Readings per Second:",
  value: 1,
  step: 0.001
}) : null

viewof overheadPercent = calculationType === "Data Rate" ? Inputs.range([0, 100], {
  label: "Protocol Overhead (%):",
  value: 20,
  step: 5
}) : null

dataRateResult = {
  if (calculationType !== "Data Rate") return null;

  const rawBytesPerSec = sensorCount * bytesPerReading * readingsPerSecond;
  const withOverhead = rawBytesPerSec * (1 + overheadPercent / 100);
  const bitsPerSec = withOverhead * 8;
  const mbPerDay = (withOverhead * 86400) / (1024 * 1024);
  const gbPerMonth = (mbPerDay * 30) / 1024;

  return html`
    <div style="background: #E8DAEF; padding: 20px; border-radius: 12px; margin: 20px 0;">
      <h4 style="margin-top: 0; color: #9B59B6;">Data Rate Requirements</h4>

      <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 15px;">
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Raw Data Rate</div>
          <div style="font-size: 20px; font-weight: bold; color: #2C3E50;">
            ${rawBytesPerSec < 1024 ? rawBytesPerSec.toFixed(1) + ' B/s' : (rawBytesPerSec / 1024).toFixed(2) + ' KB/s'}
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">With Overhead</div>
          <div style="font-size: 20px; font-weight: bold; color: #E67E22;">
            ${bitsPerSec < 1000 ? bitsPerSec.toFixed(0) + ' bps' : (bitsPerSec / 1000).toFixed(2) + ' kbps'}
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Per Day</div>
          <div style="font-size: 20px; font-weight: bold; color: #3498DB;">
            ${mbPerDay < 1 ? (mbPerDay * 1024).toFixed(1) + ' KB' : mbPerDay.toFixed(1) + ' MB'}
          </div>
        </div>
        <div style="background: white; padding: 12px; border-radius: 8px; text-align: center;">
          <div style="font-size: 11px; color: #666;">Per Month</div>
          <div style="font-size: 20px; font-weight: bold; color: #27AE60;">
            ${gbPerMonth < 1 ? (gbPerMonth * 1024).toFixed(1) + ' MB' : gbPerMonth.toFixed(2) + ' GB'}
          </div>
        </div>
      </div>
    </div>
  `;
}

dataRateResult

unitConvertCalc = {
  if (calculationType !== "Unit Converter") return null;

  return html`
    <div style="background: linear-gradient(135deg, #FADBD8 0%, #F5B7B1 100%); padding: 25px; border-radius: 12px;">
      <h3 style="margin-top: 0; color: #E74C3C;">Unit Converter</h3>
      <p style="color: #666;">Convert between common IoT units.</p>
    </div>
  `;
}

unitConvertCalc

viewof conversionType = calculationType === "Unit Converter" ? Inputs.radio(
  ["dBm ↔ mW", "Frequency", "Data Size", "Time"],
  {label: "Convert:", value: "dBm ↔ mW"}
) : null

viewof inputValue = calculationType === "Unit Converter" ? Inputs.range([-50, 50], {
  label: conversionType === "dBm ↔ mW" ? "dBm value:" :
         conversionType === "Frequency" ? "MHz value:" :
         conversionType === "Data Size" ? "KB value:" : "ms value:",
  value: 0,
  step: 0.1
}) : null

unitResult = {
  if (calculationType !== "Unit Converter") return null;

  let results = [];

  if (conversionType === "dBm ↔ mW") {
    const mw = Math.pow(10, inputValue / 10);
    const dbmFromMw = 10 * Math.log10(Math.abs(inputValue) || 0.001);
    results = [
      {label: "dBm → mW", value: inputValue + " dBm = " + (mw < 0.01 ? (mw * 1000).toFixed(3) + " uW" : mw.toFixed(4) + " mW")},
      {label: "mW → dBm", value: Math.abs(inputValue) + " mW = " + dbmFromMw.toFixed(2) + " dBm"}
    ];
  } else if (conversionType === "Frequency") {
    results = [
      {label: "MHz → Hz", value: inputValue + " MHz = " + (inputValue * 1e6).toLocaleString() + " Hz"},
      {label: "MHz → GHz", value: inputValue + " MHz = " + (inputValue / 1000).toFixed(4) + " GHz"},
      {label: "Wavelength", value: "λ = " + (299792458 / (inputValue * 1e6)).toFixed(2) + " m"}
    ];
  } else if (conversionType === "Data Size") {
    results = [
      {label: "KB → Bytes", value: inputValue + " KB = " + (inputValue * 1024).toLocaleString() + " bytes"},
      {label: "KB → MB", value: inputValue + " KB = " + (inputValue / 1024).toFixed(4) + " MB"},
      {label: "KB → bits", value: inputValue + " KB = " + (inputValue * 8192).toLocaleString() + " bits"}
    ];
  } else {
    results = [
      {label: "ms → seconds", value: inputValue + " ms = " + (inputValue / 1000).toFixed(4) + " s"},
      {label: "ms → microseconds", value: inputValue + " ms = " + (inputValue * 1000).toLocaleString() + " us"},
      {label: "Frequency", value: "1/" + inputValue + " ms = " + (1000 / inputValue).toFixed(2) + " Hz"}
    ];
  }

  return html`
    <div style="background: #F5B7B1; padding: 20px; border-radius: 12px; margin: 20px 0;">
      <h4 style="margin-top: 0; color: #E74C3C;">Conversion Results</h4>
      ${results.map(r => html`
        <div style="background: white; padding: 12px; border-radius: 8px; margin: 10px 0;">
          <strong>${r.label}:</strong> ${r.value}
        </div>
      `)}
    </div>
  `;
}

unitResult

---

74.4 Export Results

exportData = {
  const timestamp = new Date().toISOString();
  const tool = "IoT Formula Calculator";

  if (calculationType === "Link Budget") {
    const fspl = 20 * Math.log10(distanceM) + 20 * Math.log10(frequencyMhz * 1e6) - 147.55;
    const eirp = txPowerDbm + txAntennaGain;
    const rxPower = eirp - fspl + rxAntennaGain;
    const margin = rxPower - rxSensitivity;

    return {
      title: "Link Budget Calculation",
      tool: tool,
      timestamp: timestamp,
      inputs: {
        txPower: txPowerDbm + " dBm",
        txAntennaGain: txAntennaGain + " dBi",
        rxAntennaGain: rxAntennaGain + " dBi",
        distance: distanceM + " m",
        frequency: frequencyMhz + " MHz",
        rxSensitivity: rxSensitivity + " dBm"
      },
      results: {
        eirp: eirp.toFixed(1) + " dBm",
        pathLoss: fspl.toFixed(1) + " dB",
        rxPower: rxPower.toFixed(1) + " dBm",
        linkMargin: margin.toFixed(1) + " dB",
        linkViable: margin > 0 ? "Yes" : "No"
      }
    };
  }

  if (calculationType === "Battery Life") {
    const avgCurrent = (activeCurrent * activeTimePercent / 100) + (sleepCurrent * (100 - activeTimePercent) / 100);
    const effectiveCapacity = batteryCapacity * batteryEfficiency / 100;
    const lifeHours = effectiveCapacity / avgCurrent;

    return {
      title: "Battery Life Calculation",
      tool: tool,
      timestamp: timestamp,
      inputs: {
        batteryCapacity: batteryCapacity + " mAh",
        activeCurrent: activeCurrent + " mA",
        sleepCurrent: sleepCurrent + " mA",
        activeTime: activeTimePercent + " %",
        usableCapacity: batteryEfficiency + " %"
      },
      results: {
        averageCurrent: avgCurrent.toFixed(3) + " mA",
        effectiveCapacity: effectiveCapacity.toFixed(0) + " mAh",
        batteryLifeHours: lifeHours.toFixed(1) + " hours",
        batteryLifeDays: (lifeHours / 24).toFixed(1) + " days",
        batteryLifeYears: (lifeHours / 8760).toFixed(2) + " years"
      }
    };
  }

  return {
    title: calculationType + " Results",
    tool: tool,
    timestamp: timestamp,
    inputs: {},
    results: { message: "Select Link Budget or Battery Life for detailed export" }
  };
}

// Export buttons
html`
<div style="background: #f8f9fa; padding: 15px; border-radius: 10px; margin: 15px 0;">
  <strong style="display: block; margin-bottom: 10px;">Export Your Results:</strong>
  <div style="display: flex; gap: 10px; flex-wrap: wrap;">
    <button onclick="
      const data = ${JSON.stringify(exportData)};
      navigator.clipboard.writeText(JSON.stringify(data, null, 2));
      this.textContent = 'Copied!';
      setTimeout(() => this.textContent = 'Copy JSON', 1500);
    " style="padding: 8px 16px; background: #2C3E50; color: white; border: none; border-radius: 6px; cursor: pointer;">
      Copy JSON
    </button>
    <button onclick="
      const data = ${JSON.stringify(exportData)};
      let md = '## ' + data.title + '\\n\\n';
      md += '**Generated:** ' + new Date(data.timestamp).toLocaleString() + '\\n\\n';
      md += '### Inputs\\n';
      for (const [k,v] of Object.entries(data.inputs)) md += '- **' + k + ':** ' + v + '\\n';
      md += '\\n### Results\\n';
      for (const [k,v] of Object.entries(data.results)) md += '- **' + k + ':** ' + v + '\\n';
      navigator.clipboard.writeText(md);
      this.textContent = 'Copied!';
      setTimeout(() => this.textContent = 'Copy Markdown', 1500);
    " style="padding: 8px 16px; background: #16A085; color: white; border: none; border-radius: 6px; cursor: pointer;">
      Copy Markdown
    </button>
    <button onclick="
      const data = ${JSON.stringify(exportData)};
      const blob = new Blob([JSON.stringify(data, null, 2)], {type: 'application/json'});
      const url = URL.createObjectURL(blob);
      const a = document.createElement('a');
      a.href = url;
      a.download = 'iot-calculation-' + Date.now() + '.json';
      a.click();
    " style="padding: 8px 16px; background: #E67E22; color: white; border: none; border-radius: 6px; cursor: pointer;">
      Download JSON
    </button>
  </div>
</div>
`

---

74.5 Quick Reference

Formula	Equation	Example
FSPL	20log(d) + 20log(f) - 147.55	1km @ 868MHz = 91.3dB
Link Budget	Ptx + Gtx - PathLoss + Grx	14 + 2 - 91 + 2 = -73dBm
Battery Life	Capacity / Avg_Current	2000mAh / 0.1mA = 20000h
ADC Step	Vref / 2^bits	3.3V / 4096 = 0.8mV
Nyquist	Fs > 2 × Fmax	1kHz signal → > 2kHz sample
SNR (ADC)	6.02 × bits + 1.76	12-bit = 74dB

---

74.6 Related Resources

• Quick Reference Cards - Protocol cheat sheets
• Wireless Range Calculator - Detailed link budget tool
• ADC Resolution Visualizer - Visual ADC exploration
• Power Budget Calculator - Battery life estimation