Battery Design for Reliability (DFR) & Design for Service (DFS)

Like other engineering disciplines, Design for Reliability (DFR) and Design for Service (DFS) are critical elements of product development. At the early design stage for electronic safety compliance, both methodologies must be integrated into the overall lithium-ion battery development scheme.

DFR is a systematic concurrent engineering practice spanning the full product lifecycle, aiming to secure stable performance and durability throughout service life. As defined in the Reliability Edge Quarterly Newsletter: “Design for Reliability is a systematic, streamlined concurrent engineering process in which reliability engineering is embedded into the overall product development cycle.” Rather than an isolated standalone procedure, DFR consists of a complete engineering toolkit including Failure Modes and Effects Analysis (FMEA), Test to Failure (TTF), accelerated life testing, Voice of the Customer (VOC) research, and Design of Experiments (DOE).

The biggest obstacle in reliability assessment is its heavy reliance on historical performance data for failure forecasting. Lithium-ion battery technology has a relatively short development history, resulting in insufficient accumulated statistical data to accurately predict long-term failure trends. While lithium-ion cells are widely deployed in portable electronics such as laptops and smartphones, such products differ drastically from large-scale energy storage systems in system complexity and operating environments. Accordingly, design, production and field service experience from consumer batteries provides minimal reference value for grid-scale energy storage projects.

DFS is rooted in upfront engineering to resolve maintainability challenges in early-stage development. One common design adopts mechanical fasteners to assemble cells, enabling single-cell replacement and setting the individual cell as the Smallest Replaceable Unit (SRU). Nevertheless, this configuration carries latent risks: fasteners may loosen over ageing and vibration, triggering premature battery failure. Alternatively, many manufacturers employ welding instead of mechanical clamping, which defines modules rather than single cells as the SRU. Though this drives up after-sales maintenance costs, welded interconnection drastically reduces long-term failure probability. In addition, DFS engineers also incorporate recyclability, second-life repurposing and remanufacturing into design specifications. Such construction facilitates easy disassembly and clear identification of core components, which will grow increasingly vital as the large-format battery energy storage industry matures.

In summary, DFS optimizes pack construction to simplify field inspection and component replacement; DFR analyzes all potential failure modes of the battery pack to formulate targeted failure mitigation solutions.