Battery Packs in EVs/HEVs:
-
Consist of hundreds of cells, delivering around 400 V to power electric motors.
-
Monitored and managed by a Battery Management System (BMS).
-
Charged via an onboard AC/DC converter module, with charging voltages ranging from 110 V (single-phase) to 380 V (three-phase).
-
Role of the BMS:
-
Extends battery lifespan and enhances vehicle range.
-
Tracks key metrics: State of Health (SoH), State of Charge (SoC), and Depth of Discharge (DoD).
-
Monitors individual cells to address capacity degradation over time.
-
Balances cells during charging and discharging to maintain uniformity.
-
-
Challenges in Battery Packs:
-
Aging cells lose capacity, reducing the overall battery pack performance.
-
Variations in SoC, impedance, and capacity increase with the number of cells.
-
A single underperforming cell in a series stack can cause divergence in SoC over multiple cycles.
-
-
Battery Monitoring and Protection:
-
Ensures optimal performance during charging and discharging.
-
Incorporates components for voltage/current measurement, signal isolation, and safety monitoring.
-
Critical for Li-ion battery packs, which are prone to catastrophic failures from overvoltage.
-
-
Example: Texas Instruments’ BQ76PL536A:
-
Designed for Li-ion cell balancing and monitoring.
-
Stackable protector and analog front-end for 3 to 6 series cells per pack.
-
Features include a high-accuracy ADC, independent voltage/temperature protection, cell balancing, and a precision 5 V regulator.
-
Multiple devices can be stacked to monitor up to 192 cells without additional isolation components.
-
Protects against overcharge, overdischarge, and overtemperature, ensuring system safety.
-