We’ve just completed the servicing of a US2000B battery, and here’s a breakdown of the work done, observations made, and recommendations for optimal performance.
Service Overview
We performed the following tasks to ensure the battery is in the best possible condition before returning it:
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Top Balance to 100% SOC – Cells were charged to 3.55V, achieving an overall imbalance of just 30mV.
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Discharge Test at 25A – The battery was discharged down to 20% SOC. We noted that:
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A higher imbalance (50mV) was observed in the 99-88% and 30-20% SOC ranges.
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The middle SOC range was stable with an imbalance of only 15mV.
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Firmware Update – The BMS was flashed with the latest firmware (V3.4) for improved performance.
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SOC Reset & Calibration – Ensured accurate state-of-charge readings for better system integration.
Observations & Recommendations
1. SOC Management
The event logs reveal that the battery frequently discharges below 20% SOC multiple times per month. If possible, we recommend adjusting the system’s discharge threshold to 30% SOC or higher to prevent deep discharge cycles, which can accelerate cell degradation.
2. Cell Imbalance – Focus on Cell 6
Cell 6 appears to be the weakest link in this battery. During our top balancing process, we observed:
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It was the first to reach 3.55V.
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It was also the fastest to settle at an idle voltage of 3.4V.
This suggests increased internal resistance (IR) in Cell 6, likely the root cause of the imbalance observed during cycling.
3. Managing Cell Balancing
Due to the imbalance tendencies, ongoing management is key to maintaining battery health. Here are our top recommendations:
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Charge to 100% SOC periodically – This allows the passive balancing circuit to even out cell voltages effectively.
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Keep the SOC within 30-80% – Staying within this range will help prevent noticeable imbalance. LiFePO4 cells maintain a relatively flat voltage curve in this region, avoiding the rapid voltage swings seen outside this range.
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Avoid high charge currents above 80% SOC – Once past 80%, Cell 6’s voltage rises rapidly when charging currents exceed 1A, which can trigger high-voltage alarms.
Final Thoughts
This battery is still functional but should be considered for light-duty applications. While it will charge to 100% SOC, it does so at a lower charge current from around 80% SOC onwards. For best results, we strongly advise keeping it cycling between 30%-80% SOC whenever possible to extend its service life and minimize balance drift.
If you have any questions or need further guidance, feel free to reach out!