Ford’s Key Life Battery test for Li-ion batteries simulates 10 years, 150K miles in 10 months, under different conditions
12 December 2012
Leveraging some 20 years of experience and data reaching back to its early work with hybrids and the Ranger EV, Ford has developed a battery model and life validation protocol it now uses to predict how lithium-ion batteries are likely to perform under 10 years and 150,000 miles of use (40-season equivalent key life tests). The Key Life Test (KLT) takes about 10 months to complete.
Ford had earlier developed a NiMH battery model for use in KLTs, as detailed in a 2010 paper by a Ford team (Yang et al.) published in the International Journal of Energy Research. A detailed core model incorporating critical degradation mechanisms of battery components under various usage profiles is key to the testing. The Li-ion KLT test allows engineers to simulate many factors affecting the Li-ion batteries, including location of a battery within a vehicle; the temperatures they might have to endure; and various kinds of acceleration and stopping that different drivers would apply.
Other battery tests include simulating hot and sunny Phoenix weather by subjecting batteries to greater than 140 °F (60 °C) temperatures, extreme cold conditions in Manitoba, Canada with -40 °F (-40 °C) tests, and by driving vehicles equipped with the batteries through ditches filled with water to ensure there are no issues.
Battery reliability ranks as the single-most important purchase consideration by potential hybrid customers, topping 17 other factors such as fuel economy and number of safety features, according to a recent Ford-commissioned survey. The Key Life Test aims at delivering higher-quality and even more reliable batteries, said Kevin Layden, director of Ford Electrification Programs.
Ford began working with hybrid vehicle technology in the late 1980s. The company offered a limited release of the Ranger EV in 1998, the Escape Hybrid in 2004 and the Fusion Hybrid in 2009. Ford draws on the data it collected from these previous-generation efforts, especially the higher volume production hybrids.
For example, 50 million battery cells have been produced since 2004 in previous-generation production Ford hybrid vehicles such as the Escape Hybrid and Fusion Hybrid. Some of these have been put to use in taxi fleets in such cities as San Francisco and New York, with some taxi vehicles attaining more than 250,000 miles individually and taxi fleets in California alone attaining a total of nearly 100 million miles.
Of all Ford production hybrid vehicles produced to date, only six battery cells have failed of the 50 million that were put into use, the company said.
We can’t do an apples-to-apples comparison between the nickel-metal-hydride and lithium-ion batteries, but we can evaluate much of the data collected to see how hybrid vehicles are driven, the kinds of conditions they face and the demands that are placed on them. Knowing all of that helps us benchmark our tests and ensure the lithium-ion batteries are meeting or exceeding expectations.—Mazen Hammoud, chief engineer, Electrified Powertrain Systems
Ford is investing $135 million in the design, engineering and production of key components—including doubling its battery testing capabilities—for the five electrified vehicles the company will have in its portfolio by the end of the year: Fusion Hybrid, Fusion Energi plug-in hybrid, C-MAX Hybrid, C-MAX Energi plug-in hybrid and Focus Electric.
Ford also now has more than 1,000 engineers working on vehicle electrification, which is headquartered at its 285,000-square-foot Advanced Electrification Center in Dearborn.
Ford says it has reduced the cost of its current hybrid system by 30% compared with previous-generation technology and vehicles are coming to market 25% faster.
Yang, X. G., Taenaka, B., Miller, T. and Snyder, K. (2010), Modeling validation of key life test for hybrid electric vehicle batteries. Int. J. Energy Res., 34: 171–181. doi: 10.1002/er.1657
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