How the Health Score Works

CellPulse reads raw data directly from your car's Battery Management System (BMS) via the OBD-II port. The health score is computed from this data — no guessing, no AI, no estimates.

Four Independent Checks

The score is based on four factors. Each one is rated independently on a 5-star scale:

Factor	What It Measures
Cell Balance	Voltage spread between the strongest and weakest cell (mV)
Temperature Delta	Difference between hottest and coldest battery sensor (°C)
SOC Spread	Difference in state of charge between strongest and weakest cell (%)
Charge Rate	Current charge limit vs the pack's nominal maximum (%)

Star Thresholds

	★★★★★	★★★★	★★★	★★	★
Cell Balance	<10 mV	<20	<40	<60	>60
Temperature Delta	<1°C	<3	<5	<10	>10
SOC Spread	<1%	<2	<4	<8	>8
Charge Rate	>90%	>75%	>50%	>25%	<25%

Overall Score

The star rating and the numeric score are complementary:

Stars show your weakest area — the one factor to watch. The lowest-rated factor determines the star rating. This ensures a single problem can't hide behind strong averages.

The number (0–100) reflects overall pack condition across all factors. It's the average of all active factor ratings (★=20, ★★=40, ★★★=60, ★★★★=80, ★★★★★=100).

A pack scoring ★★★★ 93/100 is stronger than ★★★★ 80/100, even though both are "Healthy." The stars flag the weakest link, the number gives nuance.

Thresholds will evolve. The current values are initial estimates based on MEB pack data from the OBD community and our own testing. As we collect more scans, we'll recalibrate based on actual distributions across pack variants and mileage bands.

Cold Battery

If the battery temperature is below 15°C, the charge rate factor is skipped. Cold batteries naturally limit charge speed — this is temperature protection, not degradation. The report notes this with a snowflake icon.

For the most accurate score, scan when the battery has had time to warm up (after driving, or in moderate weather). Cell balance and capacity are less affected by temperature.

What the Score Doesn't Tell You

Total capacity loss — the score measures cell balance and charge rate, not how many kWh the pack has lost since new. We're working on adding direct energy measurements.
Comparison to other cars — the score is currently absolute (fixed thresholds). Once we have enough scans, we'll add percentile ranking ("better than 87% of similar cars").
Remaining range — CellPulse doesn't estimate range. It tells you whether the cells are healthy and balanced.

Example: 86/100 ★★★★ Healthy

Cell Balance: 14 mV spread ★★★★

Temperature: 0.4°C spread ★★★★★

SOC Spread: 1.3% ★★★★

Charge Rate: skipped (battery cold at 7°C)

Overall = ★★★★ (weakest active factor). Numeric = (80 + 100 + 80) / 3 = 86.

Raw Data

Every number in the score comes from raw BMS data — cell voltages, temperatures, SOC readings, and charge limits. The report shows all of this alongside the score. Nothing is hidden.