--- title: TWAICE Safety Anomaly Index description: "The TWAICE Safety Anomaly Index explained: how it assesses safety-relevant anomalies in your BESS and how to use it to prioritize actions." --- [Skip to content](https://support.twaice.com/knowledge/twaice-safety-index#main-content) ![TWAICE Help CenterWordmark (2)](https://support.twaice.com/hs-fs/hubfs/Wordmark%20(2).png?width=138&height=28&name=Wordmark%20(2).png) Open main navigation Close main navigation - [Contact us](mailto:support@twaice.com) [Contact us](mailto:support@twaice.com) How can we help you? - There are no suggestions because the search field is empty. 1. [Help Center](https://support.twaice.com/knowledge?hsLang=en) 2. [TWAICE KPIs](https://support.twaice.com/knowledge/twaice-kpis?hsLang=en) # TWAICE Safety Anomaly Index ## Learn what the TWAICE Safety Anomaly Index shows in the Anomalies column of the Portfolio Overview, how it is calculated and how to use it. The TWAICE Safety Anomaly Index is shown in the Anomalies column of the Portfolio Overview and reflects the most critical state of the Anomalies section. ### What does the TWAICE Safety Anomaly Index represent? The safety status is a metric that measures the overall safety status of an entire BESS system. It is calculated by taking into account the anomalous measurements of temperature, resistance and self-discharge from all components in the system within a defined time period. ### How is the Safety Anomaly Index calculated? Components with significant anomalies will get flagged with label of **"Action Recommended"** or **"Action Required"** based on the following classification. For this classification, strings are compared with their siblings based on statistical analysis. Outlier components are identified if they deviate significantly from the average, based on how far they are compared to the typical spread of the data. This involves checking if the difference from the average is at least twice the standard amount of variation and meets specific thresholds for both absolute and relative deviation. This logic is applied similarly for temperature and resistance. However, the exact configuration is different for the two KPIs due to different properties. - For the [temperature](https://support.twaice.com/knowledge/what-to-do-about-high-temperature-alerts-in-your-bess?hsLang=en) an action is recommended if a string was an outlier for at least 24 hours of the last 14 days and if the issue was still present in the last 3 days. Additionally if there was a high temperature deviation of at least 20 °C, an action is required as it indicates that this component was running abnormally hotter than all other ones. - As the [DC resistance](https://support.twaice.com/knowledge/dc-resistance?hsLang=en) is more stable and slowly changing in comparison, the introspected time-range is extended to 60 days. During that time-range a single string needs to be an outlier for at least 90 % of the time, so that there is an recommended action. - A [self-discharge](https://support.twaice.com/knowledge/detecting-self-discharge-anomalies?hsLang=en) anomaly is flagged when the minimum cell voltage in a string is consistently and significantly lower - by at least 100mV in 90% of readings - than that of other strings over a period of time. For NMC chemistries, if this condition lasts less than 5 days, it is marked as "action recommended" (yellow), but if it persists for more than 5 days, it escalates to "action required" (red), as the string may be experiencing ongoing self-discharge and should not simply be recharged without further investigation. The red status remains until the voltage deviation is no longer detected. In contrast, for LFP chemistries, this issue is less critical and always results in "action recommended" (yellow), regardless of duration. The Safety Anomaly Index aggregates those string-level observations to a storage level, by taking the most severe status of a single string. This means that if at least a single string either has required or recommended actions, the same holds true for the storage. ⚠️ ***Important Note:*** *Systems with a **1:1 rack-to-DC Combiner mapping** currently have a **limitation in detecting self-discharge anomalies** — these cases cannot yet be identified as of now.* *We are actively working to **enhance the algorithm** to address this scenario.* *👉 Please get in touch with your **TWAICE contact** for more details or guidance on this limitation.* ### Using the TWAICE Safety Anomaly Index The TWAICE Safety Anomaly Index is a valuable tool for assessing the otherwise abstract safety status of a system. It can be used to identify areas where actions are needed and to track the progress of safety initiatives. © 2026 TWAICE Technologies GmbH [twaice.com](https://www.twaice.com)      [Privacy](https://www.twaice.com/legal/data-protection-notice)      [Imprint](https://www.twaice.com/legal/legal-notice)