Battery State of Safety (SOS)

SOC and SOH are both energy-domain metrics derived from electrical measurement. They are excellent at describing performance and poor at describing risk, because a pack can hold nominal capacity and still contain a cell with a developing internal short.

SOS is a risk-domain metric. It answers a different question: given what this pack is doing chemically, thermally and electrically right now, and given its age, chemistry and duty history, how much margin remains before an uncontrollable event becomes likely?

Battery Sense composes SOS from several input classes. Molecular data provides chemical selectivity and quantification at cell, module and rack level. Environmental data adds flow and pressure. Electrical data from the BMS and EMS supplies voltage, current and impedance context. Contextual data — chemistry, manufacturer, pack age, cycle count, warranty terms and second-life status — determines how the same gas reading should be interpreted for that asset.

The output is not a single number for a site. It is a distributed index, so a single degrading module raises its own SOS score and the rack it belongs to, without hiding inside a site-wide average.

• Molecular: H₂, electrolyte VOC, CO concentration and trend
• Environmental: temperature, humidity, flow, pressure
• Electrical: voltage, current, impedance, balancing behaviour
• Contextual: chemistry, manufacturer, age, cycle count, warranty and second-life status

Using distributed hydrogen sensing combined with thermal and impedance correlation, the platform creates a live digital heat map of an entire installation — from cell and module level through to rack and pack. Operators can visualise abnormal gas generation, identify the exact location of first venting and understand how failure conditions propagate in real time.

That heat map is the practical form of a battery digital twin: not a physics simulation detached from the asset, but a continuously measured representation of where risk actually sits.

Without an SOS measurement, safety margin is handled by assumption — conservative derating, fixed maintenance intervals, and warranty terms written around worst-case degradation. That is expensive in energy throughput and in avoidable service visits.

With SOS, operation becomes evidence-based. Assets with high margin run closer to their performance envelope; assets with degrading margin get attention before they fail. Battery Sense's Second Sight nodes are built around three outcomes: maximise the energy you get, decrease downtime, and catch hidden battery risk as cells age.