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  <div class="header">
    <div style="font-weight:800">Battery Health Indicator – Methodology</div>

  </div>
  <div class="container">
    <div class="card">
      <h2>Core idea</h2>
      <p>The BHI estimates remaining capacity from OCPP charging data, using only stable charging phases (after initial warm‑up).
      Processing runs <b>offline overnight</b>.</p>
      <ul>
        <li><b>Stable phase:</b> analysis starts ≈10–20&nbsp;min after start (AC), 5% SoC change on DC or when stability criteria are met ().</li>
        <li><b>Capacity estimate:</b> <code>Capacity ≈ 100% × ΔE / ΔSoC</code> from delivered energy (kWh) and SoC change (%).</li>
        <li><b>BHI/SoH:</b> <code>BHI ≈ (current capacity / reference) × 100%</code>. Without OEM data, the first robust session becomes the baseline.</li>
        <li><b>Self‑comparison:</b> evaluate vehicle vs. its own history, split by AC/DC and temperature bands.</li>
      </ul>
    </div>

    <div id="confidence" class="card">
      <h2>Confidence model</h2>
      <p>Confidence (0–100%) quantifies reliability of the current BHI:</p>
      <ul>
        <li><b>Session coverage (35 pts):</b> share of eligible sessions (ΔSoC ≥ 20 pp) in 30 d (up to 40 sessions → full points).</li>
        <li><b>Stability (25 pts):</b> low std. deviation of BHI in last 30 d → more points.</li>
        <li><b>AC/DC mix (15 pts):</b> balanced coverage (~50/50) → maximum.</li>
        <li><b>ΔSoC span (15 pts):</b> median span per evaluated window (≥ 35 pp → maximum).</li>
        <li><b>Temperature coverage (10 pts):</b> share of sessions within 5–30 °C.</li>
      </ul>
      <p><b>Buckets:</b> high ≥ 70 %, medium 40–69 %, low &lt; 40 %.</p>
    </div>

    <div id="thresholds" class="card">
      <h2>Thresholds & status</h2>
      <p><b>critical</b> if <code>BHI &lt; 80%</code> <i>OR</i> <code>Δ30d ≤ −3.0 pp</code> <i>OR</i> <code>Δ90d ≤ −6.0 pp</code>.<br/>
         <b>watch</b> (if not critical) if <code>BHI &lt; 85%</code> <i>OR</i> <code>Δ30d ≤ −2.0 pp</code> <i>OR</i> <code>Δ90d ≤ −4.0 pp</code>.<br/>
         <b>ok</b> otherwise.</p>
      <p>Thresholds are configurable per OEM/use case.</p>
    </div>

    <div id="refs" class="card">
      <h2>Reference SoH & correlation</h2>
      <p>The dashboard integrates two reference signals:</p>
      <ul>
        <li><b>OEM SoH (daily):</b> direct SoH reported by the vehicle/OEM, shown with date and latest value.</li>
        <li><b>Manual SoH measurements:</b> lab/garage SoH tests with timestamp.</li>
      </ul>
      <p>We compute the correlation <code>r</code> (BHI↔OEM) over a 90‑day window, along with mean <b>bias</b> (BHI−OEM, in pp) and <b>MAE</b>.
      Optionally, a calibration (bias correction) can be applied if a systematic offset is proven.</p>
    </div>

    <div id="constant-window" class="card">
      <h2>Constant window detection (charging profile)</h2>
      <p>Only the <i>constant</i> SoC‑increase segment of a session is used for capacity estimates:</p>
      <ol>
        <li><b>Ignore initial warm‑up:</b> start after +5 pp SoC change from session start (controllers & auxiliaries settled).</li>
        <li><b>Find constant segment:</b> rolling slope of SoC(t) (dSoC/dt); choose the longest window with low coefficient of variation and high mean slope.</li>
        <li><b>Stop before taper:</b> end when slope drops below 70% of the stable mean (balancing phase).</li>
      </ol>
      <p>The constant window is highlighted in the per‑vehicle charging profile with two vertical markers and a shaded band.</p>
    </div>
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