Dr. Kai-Philipp Kairies working in a meetingDr. Kai-Philipp Kairies working in a meeting

This paper will explain:

Battery Management System (BMS) Failures

Watch out for BMS problems. The battery management system is supposed to monitor the proper voltage, current, and temperature of the battery cells, providing values like the State of Charge (SOC). But what if a sensor fails or the BMS logic is corrupted?

An unreliable BMS can lead to unexpected shutdowns, potentially dangerous situations, wasted resources, and issues like overcharging or deep discharging. For example, erroneous SOC calculation, leading to an underutilization of the battery asset and increasing system imbalances or deep discharging causing the dissolution of copper from the anode tab and the risk of internal short circuits – even weeks or months later.

These problems not only affect the battery's performance and safety, but also jeopardize its warranty. For instance, deep discharges during setup can void the warranty and make the battery prone to errors in the future which directly affects revenues.

The reliability of the BMS is essential to the safe and efficient operation of a BESS, ensuring optimal performance and longevity while mitigating potential risks. Detecting irregularities early allows BESS operators and owners to address them before they become bigger issues.

Voltage drift in a battery system
A poorly functioning BMS can often miss incidents of deep discharging that can render a battery unusable. ACCURE analytics detected significant undervoltage events where the BMS didn't take action.

Battery Cell Quality

Battery cell manufacturers face immense pressure to meet high market demands quickly. Increasing production can lead to higher chances of product failures, which could have severe consequences. If just one cell fails in a battery unit, it can disrupt the entire system, potentially leading to imbalances. The more cells added, the greater the risk of problems.

Cell imbalances occur when individual cells in a battery pack do not work as intended and cause capacity, voltage, or resistance variations within the pack. This, in turn, could lead to reduced battery performance, safety concerns, limited capacity utilization, increased maintenance cost, and a shortened lifetime of the batteries. For operators and owners of BESS, these issues directly impact their revenue – short and long-term. Spotting low-quality cells early in the process enables owners and operators to fix issues before they cause delays, downtime, or damage.

Deep Discharge Detection in Battery Systems
Deep Discharge Detection in Battery Systems

Cell Balancing Issues

Battery cell balancing is a crucial process in managing the health, performance, and longevity of individual cells within a battery pack, especially in BESS. The primary goal of balancing is to ensure that all cells within a battery pack reach a similar SOC and voltage.  

Cells with a lower capacity or higher resistance might discharge quicker or not perform as efficiently as others, impacting the overall energy output of the system. When some cells reach their capacity limits earlier than others due to imbalances, the entire system might stop charging or discharging too early. This reduces the effective capacity utilization of the BESS, impacting its overall efficiency and ROI. Imbalances can also lead to accelerated cell degradation and consequently to a shortened lifetime of the battery system. This reduces the overall revenue potential as the BESS would need more frequent replacements or maintenance, driving the operating cost.

Imbalances can also pose safety risks. Overcharging or over-discharging of individual cells can result in thermal runaway or damage to the entire battery pack.

State of Charge Estimation Errors

Accurate battery charge estimation matters. In a BESS, knowing the precise SOC for each cell is vital to ensure they all reach maximum capacity. However, with the shift to lithium iron phosphate (LFP) batteries, estimating SOC becomes trickier, leading to imbalance issues and financial setbacks.

SOC errors often stem from measurement inaccuracies of the BMS or misinterpretation of BMS data, which can result in misleading representations of the actual stored energy levels within the battery system. Inaccurate SOC readings may lead to inefficient energy utilization, reduced lifetime of the battery, and a compromised system reliability.

Addressing SOC errors during setup and beyond requires precise monitoring and sophisticated algorithms to ensure accurate assessments of the stored energy. Often, a simple system recalibration is the solution to minimize unnecessary balancing activities initiated by the BMS that might harm performance rather than enhance it.

State of Charge Analytics for Battery Management Systems
A real-world example of inaccurate SoC reporting from the BMS inlate-stage commissioning, and the correct information from ACCURE cloud-based analytics. Pinpointing the problem allowed for quick recalibration and the system went online with much better performance maximizing revenue.

HVAC Issues

Water damage and excessive heat can significantly harm BESS assets or lead to severe incidents. Early detection and swift identification of developing problems are crucial.

Monitoring the temperature and performance of batteries during the commissioning phases often reveals issues with the cooling or fire suppression system. A deficient cooling system causes the batteries to age prematurely, whereas water leakage can lead to a short circuit. Both damage the entire system and, in addition to safety problems, also lead to a drop in performance and possible loss of warranty.

But caring for your batteries even starts before commissioning. Do you know what happened to your batteries before they became part of your BESS? Have they been stored properly or in an overheated warehouse for extended periods? Prolonged exposure to high temperatures can lead to significant degradation. The accelerated chemical reactions within the batteries cause irreversible damage to their capacity and overall performance. Such unnoticed storage conditions might result in reduced efficiency, diminished lifespan, and compromised reliability of your BESS.

Data Informs Strategy

The commissioning phase of a BESS site is a complex and critical phase that builds the foundation for the operational life and profitability of the storage asset. This phase is critical as it sets the foundation for the performance and reliability of the storage system throughout its lifecycle. Challenges during commissioning can vary from battery quality to battery performance issues to integration complexities within the existing infrastructure.

Why can one battery system that is similar to another generate more revenue? Well, operators have to make many decisions, weighing the longevity of their battery assets. Are they are aiming for an asset lifetime of five years or extending it up to fifteen years with an optimized operational strategy? Both strategies can be correct, but they directly influence the financial return of the system.

This underlines the importance of optimized operation and maintenance strategies which can be significantly enhanced through battery analytic tools.These tools help bridge the personnel gap of battery experts and allow operators to scale, ensuring that the systems are not only maintained efficiently but also operated in a way that maximizes revenue generation.

As we advance, the integration of cutting-edge analytic tools and expertise in battery technology will be pivotal in overcoming these challenges, paving the way for more efficient and profitable BESS operations. This will not only benefit BESS owners and operators but also contribute to a more robust and sustainable energy infrastructure.

Get more insights on how to accelerate BESS commissioning in our ebook.

Senior Marketing Manager
About the author



Tania joined ACCURE in 2021 as a Senior Marketing Manager to build media relationships, coordinate marketing initiatives from content creation to trade shows, and shape the company’s brand. She closely monitors developments in the renewable energy sector and supports customers by gathering industry insights and lessons learned. When not immersed in marketing, Tania cheers for her favorite soccer team and upcycles furniture.

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About ACCURE Battery Intelligence

ACCURE helps companies reduce risk, improve performance, and maximize the business value of battery energy storage. Our predictive analytics solution simplifies the complexity of battery data to make batteries safer, more reliable, and more sustainable. By combining cutting-edge artificial intelligence with deep expert knowledge of batteries, we bring a new level of clarity to energy storage.  Today, we support customers worldwide, helping optimize the performance and safety of their battery systems. Visit us at accure.net.