--- title: "The Evolution of Electric Vehicle Battery Management Systems: From Passive to Active Cell Balancing" description: Some EV manufacturers are shifting to active cell balancing for BMS. This change impacts component selection at all levels, including capacitor selection. image: https://blog.knowlescapacitors.com/hubfs/EV%20BMS.png --- [![Knowlescapacitors](https://blog.knowlescapacitors.com/hubfs/Knowlescapacitors_September2018/Images/knowlesPDWhite250w.png)](http://www.knowlescapacitors.com/) - Capacitors - [Capacitor Overview](https://www.knowlescapacitors.com/Products/Capacitors) - [Aerospace & Defense](https://www.knowlescapacitors.com/Products/Capacitors/Aerospace-and-Defense) - [High Q](https://www.knowlescapacitors.com/Products/Capacitors/High-Q) - [SMD Capacitors](http://www.knowlescapacitors.com/Products/Capacitors/SMDCap.aspx) - [MLCCs with Leads](http://www.knowlescapacitors.com/Products/Capacitors/Leaded-MLC-s.aspx) - [Single Layer Capacitor](http://www.knowlescapacitors.com/Products/Capacitors/Single-Layer-Capacitor.aspx) - [AEC-Q200](http://www.knowlescapacitors.com/Products/Capacitors/AEC-Q200.aspx) - [Broadband Blocks](http://www.knowlescapacitors.com/Products/Capacitors/Broadband-Blocks.aspx) - [Capacitor Assemblies](http://www.knowlescapacitors.com/Products/Capacitors/CAP-Assemblies.aspx) - [Trimmer](http://www.knowlescapacitors.com/Products/Capacitors/Trimmer.aspx) - [Aluminum Capacitors](https://www.cde.com/capacitors/aluminum-electrolytic/) - [Film Capacitors](https://www.cde.com/capacitors/film-paper-film-capacitors/) - [Supercapacitors](https://www.cde.com/capacitors/ultracapacitors/) - RF and Microwave - [RF & Microwave Overview](https://www.knowlescapacitors.com/Products/Microwave-Products) - [Filter Technology](https://www.knowlescapacitors.com/Products/Microwave-Products/Filter-Technology) - [5G Filters](https://www.knowlescapacitors.com/Products/Microwave-Products/5G-Filters) - [Bandpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Bandpass-Filters.aspx) - [Lowpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Lowpass-Filters.aspx) - [Highpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Highpass-Filters.aspx) - [Cavity Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Cavity-Filters.aspx) - [Couplers](http://www.knowlescapacitors.com/Products/Microwave-Products/Couplers.aspx) - [High Frequency RF Crossover](https://www.knowlescapacitors.com/Products/Microwave-Products/RF-Crossover) - [Custom Design Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Custom-Design-Filters.aspx) - [Gain Equalizers](http://www.knowlescapacitors.com/Products/Microwave-Products/Gain-Equalizers.aspx) - [Power Dividers](http://www.knowlescapacitors.com/Products/Microwave-Products/Power-Dividers.aspx) - [Resonators](http://www.knowlescapacitors.com/Products/Microwave-Products/Resonatros.aspx) - [Ceramic Resonators](https://www.knowlescapacitors.com/Products/Microwave-Products/Ceramic-Resonators) - [Bias Filter Networks](http://www.knowlescapacitors.com/Products/Microwave-Products/Bias-Filter-Networks.aspx) - [SatCom Products](https://www.knowlescapacitors.com/Products/Microwave-Products/SatCom-Products) - [Self Bias Networks](http://www.knowlescapacitors.com/Products/Microwave-Products/Self-Bias-Networks.aspx) - EMI - [EMI Overview](https://www.knowlescapacitors.com/Products/EMI) - [EMI Filters](https://www.knowlescapacitors.com/Products/EMI/EMI-Filters) - [Planars and Discoidals](https://www.knowlescapacitors.com/Products/EMI/Planars-and-Discoidals) - Non Magnetic - [Non-Magnetic Overview](https://www.knowlescapacitors.com/Products/Non-magnetic-Components) - [Non-Magnetic Hardware](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Hardware.aspx) - [Non-Magnetic Inductors](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Inductors.aspx) - [Non-Magnetic MLC's](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Non-Magnetic.aspx) - [Non-Magnetic Trimmers](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Trimmers.aspx) - Thin Film and Substrates - [Heatsinks & Standoffs](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Heatsinks-Standoffs) - [Mounting Shorts](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Mounting-Shorts) - [Submounts](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Submounts) - [Build to Print](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Build-To-Print) - [Substrates](http://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Substrates.aspx) - Solutions - [Inductors & Baluns](https://info.knowlescapacitors.com/inductors-and-baluns) - [Military and Defense](https://info.knowlescapacitors.com/rf-and-microwave-components-for-military-and-defense) - [mmWave for 5G](https://info.knowlescapacitors.com/knowles-precision-devices-5g-filter-solutions) - [SatCom Products](https://www.knowlescapacitors.com/Solutions/SatCom-Products) - [High Reliability for Medical](https://info.knowlescapacitors.com/high-reliability-capacitors-medical-implantable) - [High Voltage for Electric Vehicles](https://info.knowlescapacitors.com/knowles-precision-devices-capacitors-for-electric-vehicles) - [Contact](http://www.knowlescapacitors.com/Contact.aspx) - [Careers](https://www.knowles.com/careers) - [Company](http://www.knowlescapacitors.com/Company.aspx) - Support - [Blog](https://blog.knowlescapacitors.com/blog) - [White Papers & Webinars](https://info.knowlescapacitors.com/resources) - [Catalogs](http://www.knowlescapacitors.com/Support/Catalogs.aspx) - [Video FAQs](https://info.knowlescapacitors.com/videos) - [Capacitor Basics](https://info.knowlescapacitors.com/knowles-precision-devices-capacitor-basics) - [Build To Print Basics](https://info.knowlescapacitors.com/build-to-print-basics) - [Filter Basics](https://info.knowlescapacitors.com/filter-basics) - [RF Components for Radar](https://info.knowlescapacitors.com/knowles-precision-devices-radar-funadamentals) - [Design Tools](http://www.knowlescapacitors.com/Support/Design-Tools.aspx) - [Product Compliance](https://info.knowlescapacitors.com/product-compliance) - [Quality](https://www.knowlescapacitors.com/Support/Quality) - [Resources](http://www.knowlescapacitors.com/Support/Resources.aspx) - [LOGIN](http://www.knowlescapacitors.com/Special-Pages/Login.aspx) - - Capacitors - [Capacitor Overview](https://www.knowlescapacitors.com/Products/Capacitors) - [Aerospace & Defense](https://www.knowlescapacitors.com/Products/Capacitors/Aerospace-and-Defense) - [High Q](https://www.knowlescapacitors.com/Products/Capacitors/High-Q) - [SMD Capacitors](http://www.knowlescapacitors.com/Products/Capacitors/SMDCap.aspx) - [MLCCs with Leads](http://www.knowlescapacitors.com/Products/Capacitors/Leaded-MLC-s.aspx) - [Single Layer Capacitor](http://www.knowlescapacitors.com/Products/Capacitors/Single-Layer-Capacitor.aspx) - [AEC-Q200](http://www.knowlescapacitors.com/Products/Capacitors/AEC-Q200.aspx) - [Broadband Blocks](http://www.knowlescapacitors.com/Products/Capacitors/Broadband-Blocks.aspx) - [Capacitor Assemblies](http://www.knowlescapacitors.com/Products/Capacitors/CAP-Assemblies.aspx) - [Trimmer](http://www.knowlescapacitors.com/Products/Capacitors/Trimmer.aspx) - [Aluminum Capacitors](https://www.cde.com/capacitors/aluminum-electrolytic/) - [Film Capacitors](https://www.cde.com/capacitors/film-paper-film-capacitors/) - [Supercapacitors](https://www.cde.com/capacitors/ultracapacitors/) - RF and Microwave - [RF & Microwave Overview](https://www.knowlescapacitors.com/Products/Microwave-Products) - [Filter Technology](https://www.knowlescapacitors.com/Products/Microwave-Products/Filter-Technology) - [5G Filters](https://www.knowlescapacitors.com/Products/Microwave-Products/5G-Filters) - [Bandpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Bandpass-Filters.aspx) - [Lowpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Lowpass-Filters.aspx) - [Highpass Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Highpass-Filters.aspx) - [Cavity Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Cavity-Filters.aspx) - [Couplers](http://www.knowlescapacitors.com/Products/Microwave-Products/Couplers.aspx) - [Custom Design Filters](http://www.knowlescapacitors.com/Products/Microwave-Products/Custom-Design-Filters.aspx) - [Gain Equalizers](http://www.knowlescapacitors.com/Products/Microwave-Products/Gain-Equalizers.aspx) - [Power Dividers](http://www.knowlescapacitors.com/Products/Microwave-Products/Power-Dividers.aspx) - [Resonators](http://www.knowlescapacitors.com/Products/Microwave-Products/Resonatros.aspx) - [Ceramic Resonators](https://www.knowlescapacitors.com/Products/Microwave-Products/Ceramic-Resonators) - [Bias Filter Networks](http://www.knowlescapacitors.com/Products/Microwave-Products/Bias-Filter-Networks.aspx) - [SatCom Products](https://www.knowlescapacitors.com/Products/Microwave-Products/SatCom-Products) - [Self Bias Networks](http://www.knowlescapacitors.com/Products/Microwave-Products/Self-Bias-Networks.aspx) - EMI - [EMI Overview](https://www.knowlescapacitors.com/Products/EMI) - [EMI Filters](https://www.knowlescapacitors.com/Products/EMI/EMI-Filters) - [Planars and Discoidals](https://www.knowlescapacitors.com/Products/EMI/Planars-and-Discoidals) - Non Magnetic - [Non-Magnetic Overview](https://www.knowlescapacitors.com/Products/Non-magnetic-Components) - [Non-Magnetic Hardware](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Hardware.aspx) - [Non-Magnetic Inductors](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Inductors.aspx) - [Non-Magnetic MLC's](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Non-Magnetic.aspx) - [Non-Magnetic Trimmers](http://www.knowlescapacitors.com/Products/Non-magnetic-Components/Trimmers.aspx) - Thin Film and Substrates - [Heatsinks, Standoffs & Submounts](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Heatsinks-Standoffs) - [Mounting Shorts](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Mounting-Shorts) - [Submounts](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Submounts) - [Build to Print](https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Build-To-Print) - [Substrates](http://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Substrates.aspx) - Solutions - [Inductors & Baluns](https://info.knowlescapacitors.com/inductors-and-baluns) - [Military and Defense](https://info.knowlescapacitors.com/rf-and-microwave-components-for-military-and-defense) - [mmWave for 5G](https://info.knowlescapacitors.com/knowles-precision-devices-5g-filter-solutions) - [SatCom Products](https://www.knowlescapacitors.com/Solutions/SatCom-Products) - [High Reliability for Medical](https://info.knowlescapacitors.com/high-reliability-capacitors-medical-implantable) - [High Voltage for Electric Vehicles](https://info.knowlescapacitors.com/knowles-precision-devices-capacitors-for-electric-vehicles) - [Contact](http://www.knowlescapacitors.com/Contact.aspx) - [Careers](https://www.knowles.com/careers) - [Company](http://www.knowlescapacitors.com/Company.aspx) - Support - [Blog](https://blog.knowlescapacitors.com/blog) - [White Papers & Webinars](https://info.knowlescapacitors.com/resources) - [Catalogs](http://dev.knowlescapacitors.com/Support/Catalogs.aspx) - [Video FAQs](https://info.knowlescapacitors.com/videos) - [Capacitor Basics](https://info.knowlescapacitors.com/knowles-precision-devices-capacitor-basics) - [Build To Print Basics](https://info.knowlescapacitors.com/build-to-print-basics) - [Filter Basics](https://info.knowlescapacitors.com/filter-basics) - [RF Components for Radar](https://info.knowlescapacitors.com/knowles-precision-devices-radar-funadamentals) - [Design Tools](http://www.knowlescapacitors.com/Support/Design-Tools.aspx) - [Quality](https://www.knowlescapacitors.com/Support/Quality) - [Product Compliance](https://info.knowlescapacitors.com/product-compliance) - [Resources](http://www.knowlescapacitors.com/Support/Resources.aspx) - [LOGIN](http://www.knowlescapacitors.com/Special-Pages/Login.aspx) - ## Knowles Precision Devices Blog # The Evolution of Electric Vehicle Battery Management Systems: From Passive to Active Cell Balancing Posted by [Jordan Yates](https://blog.knowlescapacitors.com/blog/author/jordan-yates) on Aug 16, 2023 8:30:00 AM ![Jordan Yates](https://blog.knowlescapacitors.com/hubfs/1682549265688%20copy.jpeg) - [Tweet](https://twitter.com/share) As electric vehicle (EV) manufacturers work to make batteries more affordable and easier to produce in mass quantities, we’re seeing changes in battery chemistry. For [example](https://news.ti.com/blog/2022/01/25/whats-next-in-bms-safer-more-affordable-electric-vehicles), the industry is shifting from traditional lithium ion batteries with cobalt to lithium iron phosphate (LFP) batteries. Rare-earth metals like cobalt are in short supply, and materials like LFP are a more plentiful, sustainable, and efficient alternative. ![EV BMS](https://blog.knowlescapacitors.com/hs-fs/hubfs/EV%20BMS.webp?width=1200&height=627&name=EV%20BMS.webp) At Knowles Precision Devices, we’re interested in trends in battery chemistry because they’re inspiring battery management system (BMS) advancements. A BMS is responsible for monitoring and controlling battery stack performance by managing temperature, performing state-of-charge (SoC) estimations, and carrying out cell balancing. While passive cell balancing was once the more common technique, some EV manufacturers are shifting to active cell balancing in response to BMS advancements. This change impacts component selection at all levels, including capacitor selection. BMS with active cell balancing technology calls for specially designed, high-quality capacitors. #### Active vs. Passive Cell Balancing Maintaining a healthy battery SoC extends battery life and prevents damage caused at the extremes of charging and discharging. Both active and passive cell balancing techniques aim to maintain a healthy SoC. Since weak battery cells tend to charge and discharge faster than stronger or higher capacity cells, they have more of an impact on system runtime. [Passive cell balancing](https://www.analog.com/en/technical-articles/passive-battery-cell-balancing.html#:~:text=Passive%20balancing%20allows%20the%20stack,charge%20to%20their%20maximum%20) aims to equalize the SoC among cells in the battery stack by focusing on cells with the lowest capacity, also known as “weak” cells. The goal of this technique is to make each battery in the stack look like the weakest cell in terms of capacity. Balance is accomplished using a relatively low current to drain energy from cells with a high SoC. This ensures that all cells charge to their maximum SoC, regardless of their true capacity, and that charging can continue until each cell is fully charged. While this technique achieves balance at a comparably low expense, it doesn’t improve the runtime of the system. Further, the discharge process wastes energy. Unlike passive cell balancing, which dissipates charge, [active cell balancing](https://www.analog.com/en/technical-articles/active-battery-cell-balancing.html#:~:text=Active%20cell%20balancing%20is%20a,decreasing%20heat%20generated%20while%20balancing.) redistributes charge. Active cell balancing is a more complex technique with a larger footprint, but it results in better runtime by increasing the amount of usable charge in the battery stack, as shown in Figure 1. Redistributing charge from stronger cells to weaker cells during charge and discharge cycles also decreases overall charge time and heat generation. ![BMS1](https://blog.knowlescapacitors.com/hs-fs/hubfs/BMS1.webp?width=500&height=222&name=BMS1.webp) ![BMS2](https://blog.knowlescapacitors.com/hs-fs/hubfs/BMS2.webp?width=500&height=208&name=BMS2.webp) *Figure 1: With active balancing (bottom), charge is redistributed from the stronger to weaker cells; the result is a fully depleted battery stack. With passive balancing (top), unused capacity remains. [Source.](https://www.analog.com/en/technical-articles/active-battery-cell-balancing.html#:~:text=Active%20cell%20balancing%20is%20a,decreasing%20heat%20generated%20while%20ba)* #### How Active Cell Balancing Affects Capacitor Selection Fundamental design changes, like the shift from passive to active cell balancing, require board-level adjustments—including new capacitors. Capacitors act as intermediary energy storage devices in active balancing systems throughout the charging cycle. The [“flying” capacitor](https://blog.knowlescapacitors.com/blog/what-are-flying-capacitors) multilevel inverter is emerging as a strong choice for active cell balancing since they can temporarily store and release energy; they’re particularly useful for balancing voltage levels and optimizing available voltage. Flying capacitors accomplish this by connecting to higher voltage cells during the charging phase and lower voltage cells during discharge. This concept is sometimes referred to as “[charge shuttling](https://www.batterypowertips.com/active-cell-balancing-basics/#:~:text=So%2Dcalled%20flying%20capacitors%20can,referred%20to%20as%20charge%20shuttling.).” Knowles Precision Devices’ expert team of engineers has decades of experience in high-reliability ceramic capacitors, and we’re ready to support you in selecting components to improve your BMS.  For more information, see our [AEC-Q200](https://www.knowlescapacitors.com/Products/Capacitors/AEC-Q200)-rated capacitors page or [contact us directly](https://www.knowlescapacitors.com/Contact). Topics: [Electric Vehicles](https://blog.knowlescapacitors.com/blog/tag/electric-vehicles) ## Insights Into Precision Passive Devices Knowles Precision Devices is a premier global source for Capacitors, RF Filters, EMI Filters, Resonators, non-magnetic components and advanced dielectric materials. An umbrella for the brands of **Compex**, **DLI**, **Johanson MFG**, **Novacap**, **Syfer** and **Voltronics**, Knowles Precision Devices serves a variety of markets including military, aerospace/avionics, medical equipment, implantable devices, EMI and connector filtering, oil exploration, instrumentation, industrial electronics, automotive, telecoms and data networks. This Blog will provide insights into: - Filters for 5G and mmWave - Capacitors for High Voltage - Capacitors for High Reliability and much more. Subscribe below to stay informed. ### Subscribe Here! ### Recent Posts ### Post By Topics - [Capacitor (154)](https://blog.knowlescapacitors.com/blog/tag/capacitor) - [RF and Microwave (84)](https://blog.knowlescapacitors.com/blog/tag/rf-and-microwave) - [Military and Aerospace (47)](https://blog.knowlescapacitors.com/blog/tag/military-and-aerospace) - [Filtering (36)](https://blog.knowlescapacitors.com/blog/tag/filtering) - [Medical (34)](https://blog.knowlescapacitors.com/blog/tag/medical) - Industries - [Automotive](http://www.knowlescapacitors.com/Industries/Automotive.aspx) - [Industrial](http://www.knowlescapacitors.com/Industries/Industrial.aspx) - [Medical](http://www.knowlescapacitors.com/Industries/Medical.aspx) - [Military](http://www.knowlescapacitors.com/Industries/Military.aspx) - [Space](http://www.knowlescapacitors.com/Industries/Space.aspx) - [Telecom](http://www.knowlescapacitors.com/Industries/Telecom.aspx) - Company - [About](http://www.knowlescapacitors.com/Company.aspx) - [News](http://www.knowlescapacitors.com/News.aspx) - [Quality](http://www.knowlescapacitors.com/Quality.aspx) - [Privacy Policy](https://www.knowles.com/privacy-policy) - [Terms & Conditions](http://www.knowlescapacitors.com/getattachment/Knowles-T-C.pdf.aspx?lang=en-US) - [Knowles Electronics, LLC](https://www.knowles.com/) © Knowles Capacitors All Rights Reserved ```json { "@context" : "https://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Jordan Yates", "url" : "https://blog.knowlescapacitors.com/blog/author/jordan-yates" }, "dateModified" : "2023-08-16T12:30:00.463Z", "datePublished" : "2023-08-16T12:30:00.000Z", "headline" : "The Evolution of Electric Vehicle Battery Management Systems: From Passive to Active Cell Balancing", "image" : [ "https://blog.knowlescapacitors.com/hubfs/EV%20BMS.png" ], "mainEntityOfPage" : { "@id" : "https://blog.knowlescapacitors.com/blog/the-evolution-of-electric-vehicle-battery-management-systems-from-passive-to-active-cell-balancing", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://blog.knowlescapacitors.com/hubfs/Knowles%20Corporate%20logo_blue.png" }, "name" : "Knowles Precision Devices" } } ```