Lithium-ion battery packs are at the heart of modern portable devices and are now powering a wide range of applications from electric vehicles to drones and intrinsically safe equipment. These battery packs are some of the most commonly used today and require careful planning and consideration to ensure safety, performance, and longevity. It’s important to work with a manufacturer that understands the essential aspects of designing a lithium-ion battery pack to ensure they meet the highest standards of safety and efficiency.
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Cell Selection & Matching
The first step in designing a lithium-ion battery pack is selecting the appropriate battery cells. Different lithium-ion chemistries offer varying energy densities, discharge rates, and cycle life. It's crucial to choose cells that align with the specific requirements of the application.
Cell matching is equally important. To maintain consistent performance and extend battery life, cells should be carefully matched for capacity, internal resistance, and voltage. This practice helps prevent issues like cell imbalances and overcharging.
- Battery Management System (BMS)
A robust BMS is essential for ensuring the safety and optimal performance of a lithium-ion battery pack. The BMS monitors and manages the battery's temperature, voltage, and current during charge and discharge cycles. It also prevents overcharging, over-discharging, and thermal runaway.
A well-designed BMS not only protects the battery pack from potential hazards but also optimizes its charging and discharging efficiency, thereby maximizing the battery's usable capacity and overall lifespan.
- Thermal Management
Proper thermal management is critical for lithium-ion battery packs. These batteries can generate heat during charging and discharging, and excessive heat can lead to safety issues and reduced performance.
Cell spacing, insulation, and positioning are all important aspects to designing a safe and effective long-lasting portable Lithium-Ion battery pack.
For ESS and EV, effective cooling systems, such as active cooling (fans and liquid cooling) or passive cooling (heat sinks and thermal pads), must be integrated into the battery pack design. This ensures that the cells operate within their optimal temperature range, preventing thermal runaway and maintaining overall efficiency.
- Mechanical Design & Enclosure
The mechanical design of the battery pack should prioritize structural integrity and protection for the battery cells. A robust enclosure made of fire-resistant materials helps safeguard the battery from external damage and potential hazards.
The design should also allow for expansion and contraction of cells during temperature variations, preventing undue stress on the battery components.
- Safety Features & Redundancies
Incorporating safety features and redundancies is a proactive approach to enhancing the safety of a lithium-ion battery pack. This may include individual cell fusing to prevent thermal runaway from propagating through the entire pack as well as redundant BMS components to ensure continuous monitoring and protection.
- Electrical Protection
To safeguard against electrical faults and external short circuits, the battery pack should include appropriate electrical protection measures. This may involve using high-quality fuses, circuit breakers, or contactors to isolate the battery in the event of a fault.
- Testing & Certification
Before bringing a lithium-ion battery pack to the market, rigorous testing and certification are vital. Compliance with industry standards, like UN 38.3 for transportation safety and IEC 62133 for battery performance, ensures that the battery pack meets safety and reliability requirements.
Designing a lithium-ion battery pack is a multifaceted process that demands careful attention to detail and safety. By selecting suitable cells, implementing a robust BMS, managing thermal considerations, and incorporating safety features, designers can create battery packs that deliver optimal performance, efficiency, and longevity. A well-designed and tested battery pack not only enhances the user experience but also contributes to the widespread adoption of lithium-ion technology in a myriad of portable and large format applications, propelling us towards a cleaner and more sustainable future.
Contributed by: Greg Weber
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Greg has a rich background spanning 34 years in the Rechargeable Battery Industry. Earning his BSEE from Manhattan College, he started as a battery pack design & applications engineer with Varta pivoting into OEM sales with Saft, Energizer, and GP Batteries selling both rechargeable NiCd, NiMh, and Lithium-Ion systems along with Primary battery systems in Alkaline and Lithium.
While serving as the Vice President of Global OEM Sales at Alexander Battery Technologies, Greg specialized in crafting custom-designed Lithium-Ion battery packs for OEMs. Now, as the Director of OEM Sales at Power Products Unlimited, he is at the forefront of driving new business initiatives, navigating the dynamic landscape of the Rechargeable Battery Industry, and ensuring innovative solutions for our clients.
greg.weber@powerproducts.com | T: (470) 450-2129 | M: (845) 608-5428
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Published: October 10th, 2023
