CHAPTER 5 Design for Reliability/Design for Service One of the great challenges in designing a large lithium-ion battery is estimating and calculat- ing the reliability and lifetime of the energy storage system. This is in large part due to the fact that there is not yet enough history on this technology that is available to be able to base future predictions on past performance. Therefore engineering fields like design for reliability (DFR) become very important very early in the engineering process in order to attempt to identify potential failure modes and develop mitigation strategies.
With automotive applications like the Nissan Leaf and Chevrolet Volt being on the market for about five years now, the batteries in these products are very likely only about halfway to the end of their useful life in the vehicles. The best estimates that we can draw from today are based on the many nickel metal hydride (NiMH) hybrid electric vehicles that are on the road today. Having been introduced in the late 1990s many of these are now beginning to reach the end of the vehicle’s life, typically about 12 years in the United States.
So while there are some learning that can be made from these vehicles, most of the automakers and battery manufac- turers are being very conservative in their designs so as not to incur large warranty costs if these energy storage systems reach the end of their useful life before they reach the end of their warranty period. They are using methodologies such as DFR in order to help build their confidence in the longevity of the energy storage systems. There are several relatively recent examples that exemplify the need for battery manufac- turers to implement both reliability and quality systems.
The first and perhaps the biggest recall that happened in the lithium-ion battery area was conducted by Sony in 2006 when over 10,000,000 battery packs were recalled at an estimated cost to Sony of about $429 million USD (Arendt, 2006). The reason for this particular recall may be attributed to a combination of both product and process failure modes. In this case, the 18650 type lithium-ion cells (18 mm diameter and 65 mm length) that were recalled used a nickel coated steel can with a lid that was crimped on.
Subsequent analysis indicated that during the crimping process small particles from the nickel may have been flaking off and falling into the jelly roll assembly, which in turn had the potential to cause an internal short circuit in the cell over time. In essence this was a latent failure that showed up only over time. Specific to the automotive industry, lithium-ion battery start-up A123 Systems ended up recalling more than $55 million in batteries that were introduced in the Fisker Karma (Voelcker, 2012). This was the second recall for A123 who suffered an earlier issue with coolant leakage in the Fisker battery pack.
As an early start-up company these recalls were The Handbook of Lithium-Ion Battery Pack Design. http://dx.doi.org/10.1016/B978-0-12-801456-1.00005-1 Copyright © 2015 Elsevier Inc. All rights reserved. 51