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... What makes an ideal battery management system? The first thing that should come to mind is safety ... There are many videos and articles out there that show lithium-based batteries venting and/or bursting into flames when pushed past their operating limits ... A BMS solution must prevent the battery pack from entering into an unsafe condition ... But safety is only the beginning of the story ... Users also want to maximize the life of their battery pack, and try to maintain the capacity of the battery pack as it ages ... This is where the idea of an “ideal” BMS solution can start to be defined. ... The ideal BMS solution provides accurate fuel gauging, and cell balancing to ensure that a battery back is completely empty or completely full ... There are two main design challenges to create the ideal BMS solution: ... Designing the internal battery pack topology to allow for monitoring of each cell. ... Including a mechanism for the BMS to balance the cells. ... There are three main topologies for cells in a battery pack: ... Battery Pack Topologies ... The simplest topology that allows for individual cell monitoring is a single string of series-connected battery cells ... A more complicated topology is necessary when the capacity of a battery pack needs to increase but the overall voltage needs to remain the same ... This requires a parallel connection of battery cells ... If the parallel connection occurs at the per-cell level, an approximation is made that each cell in the parallel string contributes equally to the overall health of the parallel string ... This approximation has the undesirable consequence of reducing the accuracy of the BMS ...  A parallel connection at the total pack voltage is better, as it allows the BMS to read the state of each individual cell ... It also opens the door for limp-home modes of operation ... (More on that later!) ... Just as there are multiple cell topologies, there are also multiple mechanisms for cell balancing ... Cell balancing brings each cell into alignment and ensures that each cell within the battery pack has equal state of charge (SoC) ... The Society of Automotive Engineers released a whitepaper in 2001 that describes different cell balancing solutions shown below: ... Cell balancing methods ... The simplest method to modify the level of charge of a battery cell is to apply a load to that specific cell ... This will lower the level of charge of highly charged cells to match the average level of charge ... This balancing method will provide the ideal BMS with a mechanism to ensure that the battery pack can be fully charged ... However, it doesn’t necessarily allow for the battery to be completely discharged in a useful way ... An active cell balancing method such as charge shuttling using a switched capacitor or energy conversion using a transformer allow cells nearing their end of charge level to be charged with excess energy contained in other cells still in their range of operation ... Refer to Nuvation’s recent article about cell balancing for further detail. ... Thus, to overcome the two previously mentioned BMS design challenges, it’s necessary to: ... Use a series-connected cell topology or use parallel-connected strings of series-connected cells to ensure accurate cell monitoring. ... Implement an active balancing method to allow increasing and decreasing SoC of each cell to ensure balance is achieved and maintained from completely full to completely empty. ... Resource: A Review of Cell Equalization Methods for Lithium Ion and Lithium Polymer Battery Systems.

Battery Management System Security in Utility Grids ... Concerns have been expressed by both U.S ... industry and lawmakers about the potential risks in using utility grid equipment manufactured in nations that are not strategic allies. ... ... Given the realities of global supply chains in energy storage system production, how does an energy storage company provide solutions that address the concerns of industry and legislators? Would “domestic” sourcing of an ESS fully resolve security risk concerns? What meaning can we assign to the term “domestic” considering the globally integrated supply chain used to develop the ESS? How does one determine what is and what is not a “security risk?” ... A key distinction to be made regarding security is one of passive components versus control systems ... Battery cells are passive components ... While they inherently have safety issues due the innate volatility of chemical energy storage (e.g: fire, off-gassing), it is far more difficult to tamper with a battery cell than with a control device. ... A battery management system on the other hand is a computing device that includes multiple ICs (integrated circuits / semiconductors) and sophisticated software algorithms that ensure batteries are being charged and discharged by the PCS (Power Conversion System) in a safe and performant manner ... Security risks can include: ... Hidden compromising features ... Counterfeit or tampered BMS components ... Cybersecurity/Hacking ... Download the whitepaper below to learn more about battery management system security in large-scale energy storage..

UL 1973 Battery Stack Design ... In this 3 part series, Nuvation Energy CEO Michael Worry and two of our Senior Hardware Designers explore energy storage system design from the vantage point of the battery management system ... Part 2, "Battery Stack Design for UL 1973 Certification" focuses on design for UL Certification ... Principal Hardware Designer Nate Wennyk shares his experience working with UL to create UL 1973 Recognized stack level solutions and working with energy storage system developers to create UL 1973 certifiable battery stacks. ... .

Energy Storage Designs that Maximize Supply Chain Flexibility ... Supply chain challenges will continue to affect the energy storage industry for the foreseeable future ... Lead times and costs have become increasingly unpredictable, which adds project risk ... Emerging technologies can also impact product design decisions ... In response to these risks and opportunities, energy storage system developers have begun creating supply chain agnostic ESS designs to maintain competitiveness in this rapidly changing industry. ... ... Joe O’Connor, Director of ESS Solutions at Nuvation Energy, examines ways ESS developers are reducing their project and business-risk through modular approaches to ESS design that anticipate supply chain challenges and innovation opportunities..

Introduction to the Nuvation Energy G5 BMS ... Michael Worry, CEO of Nuvation Energy walks us through the Nuvation Energy G5 High-Voltage BMS and what makes it special. ... .