--- title: Why Proper Cell Balancing is Necessary In Battery Packs description: When lithium battery packs are designed using multiple cells, it is important to design the electronic features for continuous cell balancing. image: https://blog.epectec.com/hubfs/Blog/battery-pack-using-cell-balancing.jpg --- [![Epec Engineered Technologies](https://www.epectec.com/images/logo.png "Epec Engineered Technologies")](https://www.epectec.com/) [![Epec Engineered Technologies](https://www.epectec.com/images/logo.png "Epec Engineered Technologies")](https://www.epectec.com/) - [Articles](https://www.epectec.com/articles/) - [Blog](https://blog.epectec.com/) - [Webinars](https://www.epectec.com/webinar/) - [Videos](https://www.epectec.com/videos/) - [Case Studies](https://www.epectec.com/case-studies/) - [News & Events](https://www.epectec.com/news/) - [Customer Portal](https://system.netsuite.com/c.406760/site/NSlogin.html) - [About](https://www.epectec.com/about/overview/) - Back - [Company Overview](https://www.epectec.com/about/overview/) - [Our History](https://www.epectec.com/about/our-history/) - [Culture](https://www.epectec.com/about/culture/) - [Industries Served](https://www.epectec.com/about/industry/) - [Acquisitions](https://www.epectec.com/about/acquisitions.html) - [Operations](https://www.epectec.com/operations/) - Back - [Operational Excellence](https://www.epectec.com/operations/) - [Quality Philosophy](https://www.epectec.com/operations/quality-philosophy.html) - [Quality Assurance Process](https://www.epectec.com/operations/quality-assurance-process.html) - [Global Operations](https://www.epectec.com/operations/global-operations.html) - [Logistics & Supply Chain](https://www.epectec.com/operations/logistics-and-supply-chain.html) - [Inventory Stocking](https://www.epectec.com/operations/inventory-stocking.html) - [Approvals](https://www.epectec.com/operations/approvals.html) - [ITAR Registered](https://www.epectec.com/operations/itar-registered.html) - [Engineering](https://www.epectec.com/engineering/overview/) - Back - [Engineering Overview](https://www.epectec.com/engineering/overview/) - [Engineering Support](https://www.epectec.com/engineering/support/) - [Design Services](https://www.epectec.com/engineering/design-services/) - [EpecDFx™](https://www.epectec.com/engineering/epecdfx/) - [Free DFM File Check](https://www.epectec.com/engineering/free-dfm.html) - [PCB Impedance Calculator](https://www.epectec.com/engineering/impedance-calculator.html) - [Products](https://www.epectec.com/products/) - Back - [Overview](https://www.epectec.com/products/) - [Battery Packs](https://www.epectec.com/batteries/) - [Flex & Rigid-Flex PCBS](https://www.epectec.com/flex/) - [Cable Assemblies](https://www.epectec.com/cable-assemblies/) - [Printed Circuit Boards](https://www.epectec.com/pcb/) - [CNC Machining](https://www.epectec.com/cnc-machining/) - [User Interfaces](https://www.epectec.com/user-interfaces/) - [Flexible Heaters](https://www.epectec.com/flexible-heaters/) - [EC Fans & Motors](https://www.epectec.com/fans-motors/) - [Design Guides](https://www.epectec.com/guides/) - [Design Guides](https://www.epectec.com/guides/) - Back - Resources - Back - [Articles](https://www.epectec.com/articles/) - [Blog](https://blog.epectec.com/) - [Webinars](https://www.epectec.com/webinar/) - [Videos](https://www.epectec.com/videos/) - [Case Studies](https://www.epectec.com/case-studies/) - [News & Events](https://www.epectec.com/news/) - [Customer Portal](https://system.netsuite.com/c.406760/site/NSlogin.html) - [Contact Us](https://www.epectec.com/contact/) - Back - [Contact Information](https://www.epectec.com/contact/) - [Our Sales Team](https://www.epectec.com/contact/our-sales-team.html) - [Office Locations](https://www.epectec.com/contact/office-locations.html) - [Career Opportunities](https://www.epectec.com/contact/career-opportunities.html) - [InstantPCB*Quote*™](https://www.epectec.com/instantpcbquote/) - Back - [Overview](https://www.epectec.com/instantpcbquote/) - [Login](https://secure.epecpcb.com/epec/) - [Register](https://secure.epecpcb.com/epec/index2.jsp) - [Home](https://www.epectec.com/) - [Blog](https://blog.epectec.com/) - Why Proper Cell Balancing is Necessary In Battery Packs Share This Page: [LinkedIn](https://blog.epectec.com/#linkedin) [X](https://blog.epectec.com/#x) [Facebook](https://blog.epectec.com/#facebook) [Email](https://blog.epectec.com/#email) # Why Proper Cell Balancing is Necessary In Battery Packs [![Anton Beck](https://blog.epectec.com/hubfs/Blog-Authors/anton-beck.jpg "Anton Beck")](https://blog.epectec.com/author/anton-beck) Written by [Anton Beck](https://blog.epectec.com/author/anton-beck) Posted on November 3, 2017 at 8:52 AM ![Anton Beck](https://blog.epectec.com/hubfs/Blog-Authors/anton-beck.jpg "Anton Beck") - [Tweet](https://twitter.com/share) When a [lithium battery pack](https://www.epectec.com/batteries/custom-lithium-battery-packs.html) is designed using multiple cells in series, it is very important to design the electronic features to continually balance the cell voltages. This is not only for the performance of the battery pack, but also for optimal life cycles. The use of balancing enables us to design a battery with larger capacity for an application because balancing allows the battery to achieve a higher state of charge (SOC). A lot of companies choose not to use balancing at the start of their [custom battery](https://www.epectec.com/batteries/custom/) design to reduce cost but without the investment in the cell balancing hardware and software, the design does not allow the SOC to approach 100%. [![Check Out Our Battery Pack Enclosure Design Ebook](https://no-cache.hubspot.com/cta/default/707152/89cfffe1-d865-45e0-a6a2-c47c583bfa78.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/89cfffe1-d865-45e0-a6a2-c47c583bfa78) ## How Does Cell Imbalance Occur? If lithium cells are overheated or overcharged, they are prone to accelerated cell degradation. They can catch fire or even explode as a thermal runaway condition can occur if a lithium-ion cell voltage exceeds 4.2V by even a few hundred millivolts. Every pack that we design and manufacture at Epec has an overvoltage protection circuit (sometime even a backup) to go along with standard balancing that will prevent such an event from ever occurring. In a multi-cell battery pack, which is commonly used in laptop computers and medical equipment, placing cells in series opens up the possibility of cell imbalance, a slower but persistent degradation of the battery. ## How are Cells Balanced? Cell are balanced by the process of equalizing the voltages and state of charge among the cells when they are at a full charge. No two cells are identical. There are always slight differences in the state of charge, self-discharge rate, capacity, impedance, and temperature characteristics. This is true even if the cells are the same model, same manufacturer, and same production lot. Manufacturers will sort cells by similar voltage to match as close as possible, but there are still slight variations in the individual cells impedance, capacity, and self-discharge rate that can eventually lead to a divergence in voltage over time. ![Battery Pack Using Cell Balancing](https://blog.epectec.com/hs-fs/hubfs/Blog/battery-pack-using-cell-balancing.jpg?width=600&name=battery-pack-using-cell-balancing.jpg "Battery Pack Using Cell Balancing") *Battery Pack Using Cell Balancing* Most typical battery chargers detect full charge by checking whether the voltage of the entire string of cells has reached the voltage regulation point. Individual cell voltages can vary as long as they don’t exceed the limits for overvoltage protection. However, weak cells (ones with lower capacity / higher internal impedance) tend to exhibit higher voltage than the rest of the series cells at full charge termination. These cells are then weakened further by continuous overcharge cycles. The higher voltage of the weaker cells at charge completion causes accelerated capacity degradation. If the maximal recommended charging voltage is exceeded even by as little as 10%, it will cause the degradation rate to increase by 30%. On the discharge side, the weak cells tend to have lower voltage than the other cells, due to either higher internal resistance, or a faster rate of discharge that results from the lower capacity. This means that if any of the weak cells hits the cell under voltage protection limit while the pack voltage is still sufficient to power the system, the full capacity of the battery will never be used as the pack protector will prevent over discharge (which would damage the cell) by stopping the discharge of the whole pack when one cell voltage goes below the cell under voltage threshold (usually around 2.7V).   Balancing Techniques The fundamental solution of balancing equalizes the voltage and state of charge among the cells when they are at a fully charged state. Cell balancing is typically categorized in two types: 1. Passive 2. Active ### Passive Cell Balancing The passive balancing method is somewhat simple and straight forward. Discharge the cells through a dissipative bypass route. This bypass can be either integrated or external to the integrated circuit (IC). Such an approach is favorable in low-cost system application. The fact that 100% of the excess energy from a higher energy cell is dissipated as heat makes the passive method less preferable to use during discharge because of the obvious impact on battery run time. ### Active Cell Balancing Active balancing, which utilizes capacitive or inductive charge shuttling to transfer charge between battery cells, is significantly more efficient because energy is transferred to where it is needed instead of being bled off. Of course, the trade-off for this improved efficiency is the need for additional components at higher cost. ## Summary Balancing cells is not only important for improving the performance and life cycles of the battery, it adds an element of safety to the battery. One of the emerging technologies for enhancing battery safety and extending battery life is advanced balancing. Since new cell technologies track the amount of balancing needed by individual cells, the usable life of battery packs is increased, and overall battery safety is enhanced. --- ## Key Takeaways - **Cell Balancing Maximizes Performance and Lifespan:** Proper cell balancing ensures all cells in a series battery pack maintain equal voltage, which improves performance, extends cycle life, and increases usable capacity. - **Imbalance Leads to Degradation and Safety Risks:** Even small voltage differences can cause weak cells to overcharge or over-discharge, accelerating degradation and increasing the risk of thermal runaway in lithium batteries. - **No Two Cells Are Identical:** Variations in capacity, impedance, and self-discharge rates exist even among identical cells, making balancing circuits essential to prevent long-term voltage divergence. - **Passive vs. Active Balancing:** Passive methods dissipate excess energy as heat and are more cost-effective but less efficient, while active balancing transfers charge between cells for greater efficiency at higher cost. - **Advanced Balancing Enhances Safety:** Modern active balancing technologies monitor individual cell behavior in real time, reducing stress on weaker cells, extending pack longevity, and improving overall safety. - [Tweet](https://twitter.com/share) Topics: [Battery Packs](https://blog.epectec.com/topic/battery-packs) --- [Next](https://blog.epectec.com/minimizing-risk-in-your-electronics-supply-chain) | [All posts](https://blog.epectec.com/all) | [Previous](https://blog.epectec.com/limits-and-features-of-custom-battery-packs) [![New Call-to-action](https://no-cache.hubspot.com/cta/default/707152/1ea77bbf-1c3f-462e-9e09-74f2e9727bf3.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/1ea77bbf-1c3f-462e-9e09-74f2e9727bf3) ## Leave a Comment --- ## Related Posts --- ### Recent Posts --- ### Posts by Topic - [Printed Circuit Boards (157)](https://blog.epectec.com/topic/printed-circuit-boards) - [Product Design (132)](https://blog.epectec.com/topic/product-design) - [Battery Packs (118)](https://blog.epectec.com/topic/battery-packs) - [Cable Assemblies (99)](https://blog.epectec.com/topic/cable-assemblies) - [Flex & Rigid-Flex PCB's (92)](https://blog.epectec.com/topic/flex-rigid-flex-pcbs) - [Electronics Industry (61)](https://blog.epectec.com/topic/electronics-industry) - [User Interfaces (54)](https://blog.epectec.com/topic/user-interfaces) - [Quality Solutions (32)](https://blog.epectec.com/topic/quality-solutions) - [Flexible Heaters (30)](https://blog.epectec.com/topic/flexible-heaters) - [Events, Training, and Support (9)](https://blog.epectec.com/topic/events-training-and-support) - [RF Products (7)](https://blog.epectec.com/topic/rf-products) - [CNC Machining (3)](https://blog.epectec.com/topic/cnc-machining) - [Fans & Motors (1)](https://blog.epectec.com/topic/fans-motors) See All --- --- ### Need Help with A Project? [![Request Design Support](https://blog.epectec.com/hs-fs/hubfs/blog/design-support-ad.jpg?width=350&name=design-support-ad.jpg)](https://info.epectec.com/request-design-support) Our team of engineers are here to help you with all your product needs. [Request Design Support](https://cta-redirect.hubspot.com/cta/redirect/707152/0d3cd574-22cb-48a2-867e-1a7ffba28403) Manufacturing That Eliminates Risk & Improves Reliability [sales@epectec.com](mailto:sales@epectec.com?subject=Website%20Information%20Request) [(888) 995-5171](tel:888-995-5171) ##### Support & Contact Our knowledgeable staff has many years of experience in the industry. We welcome the opportunity to put our skills to work for you! Please contact us with any questions or requests. - [176 Samuel Barnet Blvd, New Bedford, MA](https://maps.app.goo.gl/Q6JVMv3eQgw29fNY8) - [sales@epectec.com](mailto:sales@epectec.com?subject=Website%20Information%20Request) - [(888) 995-5171](tel:888-995-5171) --- ###### Certifications [![UL Certified Manufacturer](https://www.epectec.com/images/certified-ul.png "UL Certified Manufacturer")](http://www.ul.com/) [![ITAR Registered Manufacturer](https://www.epectec.com/images/certified-itar.png "ITAR Registered Manufacturer")](https://www.epectec.com/operations/itar-registered.html) [![RoHS Compliant Manufacturer](https://www.epectec.com/images/certified-rohs-compliant.png "RoHS Compliant Manufacturer")](https://www.epectec.com/pcb/rohs-compliant.html) [![ISO9001 Certified Manufacturer](https://www.epectec.com/images/certified-iso9001.png "ISO9001 Certified Manufacturer")](https://www.epectec.com/operations/approvals.html) [![ISO27001 Certified Manufacturer](https://www.epectec.com/images/certified-iso27001.png "ISO27001 Certified Manufacturer")](https://www.epectec.com/operations/approvals.html) --- - ##### About - [Company Overview](https://www.epectec.com/about/overview/) - [Our History](https://www.epectec.com/about/our-history/) - [Culture](https://www.epectec.com/about/culture/) - [Industries Served](https://www.epectec.com/about/industry/) - [Acquisitions](https://www.epectec.com/about/acquisitions.html) - ##### Operations - [Operational Excellence](https://www.epectec.com/operations/) - [Quality Philosophy](https://www.epectec.com/operations/quality-philosophy.html) - [Quality Assurance Process](https://www.epectec.com/operations/quality-assurance-process.html) - [Global Operations](https://www.epectec.com/operations/global-operations.html) - [Logistics & Supply Chain](https://www.epectec.com/operations/logistics-and-supply-chain.html) - [Inventory Stocking](https://www.epectec.com/operations/inventory-stocking.html) - [Approvals](https://www.epectec.com/operations/approvals.html) - [ITAR Registered](https://www.epectec.com/operations/itar-registered.html) - ##### Engineering - [Engineering Overview](https://www.epectec.com/engineering/overview/) - [Engineering Support](https://www.epectec.com/engineering/support/) - [Design Services](https://www.epectec.com/engineering/design-services/) - [EpecDFx™](https://www.epectec.com/engineering/epecdfx/) - [Free DFM File Check](https://www.epectec.com/engineering/free-dfm.html) - [PCB Impedance Calculator](https://www.epectec.com/engineering/impedance-calculator.html) - ##### Products - [Overview](https://www.epectec.com/products/) - [Battery Packs](https://www.epectec.com/batteries/) - [Flex & Rigid-Flex PCBS](https://www.epectec.com/flex/) - [Cable Assemblies](https://www.epectec.com/cable-assemblies/) - [Printed Circuit Boards](https://www.epectec.com/pcb/) - [CNC Machining](https://www.epectec.com/cnc-machining/) - [User Interfaces](https://www.epectec.com/user-interfaces/) - [Flexible Heaters](https://www.epectec.com/flexible-heaters/) - [EC Fans & Motors](https://www.epectec.com/fans-motors/) ##### Social Community Join our Social Community and keep in touch with all our latest technology investments, current news, upcoming events, and promotions. --- © 2026 Copyright Epec, LLC. All Rights Reserved. [Tariff Resources](https://www.epectec.com/tariff-resources/)|[Privacy Policy](https://www.epectec.com/privacy-policy/)|[Term & Conditions](https://www.epectec.com/terms/site.html)|[Sitemap](https://www.epectec.com/sitemap.html) ```json { "@context" : "https://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Anton Beck", "url" : "https://blog.epectec.com/author/anton-beck" }, "dateModified" : "2025-10-07T19:38:40.384Z", "datePublished" : "2017-11-03T12:52:18.000Z", "headline" : "Why Proper Cell Balancing is Necessary In Battery Packs", "image" : [ "https://blog.epectec.com/hubfs/Blog/battery-pack-using-cell-balancing.jpg" ], "mainEntityOfPage" : { "@id" : "https://blog.epectec.com/why-proper-cell-balancing-is-necessary-in-battery-packs", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://blog.epectec.com/hubfs/image/logo.png" }, "name" : "Epec Engineered Technologies" } } ```