What to do about low cell voltages alerts in your BESS

Understanding and Addressing Low Cell Voltages in Your Battery System

Experiencing low cell voltages in your battery system can be concerning, but understanding the potential causes and taking prompt action can help ensure the safety and optimal performance of your setup.

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What Causes Low Cell Voltages?

Significant imbalances: Uneven distribution of charge across cells can lead to some cells reaching higher voltages than others. This can occur due to:

• Faulty connections: Poor connections can cause imbalances.

• External factors: Temperature variations or uneven cooling can affect individual cells.

State of charge (SoC) and voltage misalignment: If the BMS (Battery Management System) fails to accurately measure or balance SoC and voltage, some cells might be overcharged, leading to high voltages.

Faulty BMS: A malfunctioning BMS might not properly control voltage limits, leading to overcharging.

Degraded or low-quality cells: Cells with accelerated aging or inherent manufacturing issues might reach higher voltages faster due to their limited capacity.

Self-discharge: Similar to degraded or low-quality cells, manufacturing issues can lead to an increased self-discharge rate of cells, which constantly pushes them towards lower voltage limits.

Auxiliary loads: Feeding auxiliary components (like loads from the HVAC or cooling system) with the required energy, is often performed using the existing storage energy. If longer resting periods occurre and auxiliary loads are not adjusted, the overall system is drained and low voltage levels can be reached.

What You Can Do

If you experience low cell voltage alerts, follow these steps:

Check the balancing status: Your BMS should provide information on individual cell voltages and balancing activity. Look for significant differences between cells and ensure balancing is functioning properly. TWAICE Voltage Spread and the upcoming Performance Manager solution will help you identify those.

Monitor other parameters: Beyond voltage, check for unusual temperature variations, current imbalances, or exceeded thresholds for other parameters like charge/discharge rates. These can indicate a broader BMS issue. TWAICE Safety Analytics logs all alerts. That's the place to look for more similar alerts.

Evaluate String SoH: Check the State of Health (SoH) of individual cell strings. A weak cell or large imbalances can limit the overall SoH of a string, highlighting potential issues. TWAICE Health Analytics will help you to quickly identify strings with an abnormal and low SoH.

Recurring component issues: Especially with self-discharge issues, the same cells should appear in the analysis. If the cell ID or location is available and included in the TWAICE signal mapping, either the TWAICE Data Explorer or the upcoming Performance Manager can be used to identify the individual cells or respective module which will need to be replaced.

Cross-check auxiliary loads: In case the operation is turned of or the number of cycles performed per day is reduced, validate the HVAC or cooling performance. Can it be reduced or adjusted? Cross check the impact of lower HVAC or cooling performance on the thermal management using the TWAICE Performance Manager (coming soon).

Seek professional assistance: If you're unsure about the cause or how to proceed, consult the system manufacturer for support and potential repairs or talk to our TWAICE Customer Success Experts.

Always Remember!

Early detection and intervention are crucial to preventing damage to your battery system and ensuring its continued safe and reliable operation. By understanding the potential causes of low cell voltage alerts and taking appropriate action, you can maintain the health and performance of your battery investment.

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