Software / AI

BMS Latest Innovations within Estimation Algorithms Thermal Runaway Detection

Cell Balancing

The safety philosophy of 2025 has shifted fundamentally from containment to early detection. Recognizing that measuring a temperature spike is often detecting a failure that is already irreversible, the industry has standardized on detecting the precursors to thermal runaway. These precursors - specifically the venting of electrolyte vapors and the generation of decomposition gases - offer a time window of 5 to 20 minutes before fire occurs.

Cell balancing - the process of equalizing the state of charge SoC) of series-connected cells - remains a critical function of the BMS. In 2025, the industry is witnessing a divergence in balancing strategies, driven largely by the physics of LFP chemistry and the economics of large-format cells.

Technology Type

Target Parameter

Key Product Example

Detection Capabilities

Chemical Polymer

Electrolyte Vapors DMC/EMC

Honeywell BES / BES LITE

Detects "first vent" 520 minutes prior to thermal runaway; specialized coating rejects non-battery gases

Gas Concentration

Hydrogen H2 016%

Amphenol Telaire T3600

Automotive-qualified H2 detection post-vent / pre-fire; provides ratiometric analog output to confirm anode decomposition

Multi-Physics

Pressure, VOC, Humidity, Shock

Metis Cell Guard

Combines environmental parameters to detect pack seal breaches (water ingress) and cell venting simultaneously. Validated by Sandia National Labs as over 7 minutes faster than hydrogen sensors.

LFP Challenge: LFP cells have an extremely flat OCV curve, making small voltage differences represent large SoC differences; passive balancing is too slow and heat-intensive for large packs.

Active Balancing Rise 2025: Solutions like Enerkeyʼs all-time balancing algorithm actively transfer energy (up to 20A, enabling continuous, low-heat balancing.

OEM Strategies: BYDʼs 2025 Blade Battery uses active equalization 5A, cutting balancing time 40% and ensuring consistent full-range capability. BYDʼs algorithms also determine the "high voltage turning point" of the charging curve which represents the end of the linear charging region. By finding this point, the actual capacity of the cell can be used to equalize cells based on their actual capacities instead of just the nominal capacity.

Passive Balancing Use Case: Several IC suppliers provide solutions that are still preferred in cost-sensitive, smaller systems; example: Infineon TLE9018 provides simple 300mA passive balancing suited for well-matched cells.

Source: Honeywell, Amphenol, Metis Cell Guard - EV Engineering, EnerkeyBMS, JMBatteries - BYD Blade, XRAY BYD BMS, Infineon

Extracted from the PDF; charts and images may read imperfectly.