When Ford Motor Co. announced in 2012 that its new hybrids would use lithium-ion batteries instead of nickel-metal hydride, many experts raised an eyebrow.
Lithium-ion, after all, had a reputation for high cost and unknown durability, largely because the technology was still comparatively new. In contrast, approximately 95 percent of full and mild hybrids up to that time had used nickel-metal hydride.
But Ford engineers now say their decision to use lithium-ion was based on accelerated lab tests showing lithium-ion would actually be more durable than nickel-metal hydride over a long lifetime. The tests, combined with mountains of field performance data on nickel-metal hydride, convinced them that they could predict the eight- or 10-year future of a chemistry that didn't even have five years worth of reliable field data.
"We are really confident that our Key Life Tests are mimicking the duty cycle of some of our most stringent and abusive customers," Kevin Layden, Ford's director of electrification programs and engineering, told Design News. "Given that, we feel lithium-ion will be better than nickel-metal hydride. We expect it to be absolutely stellar."
Ford's confidence in lithium-ion is based on so-called Key Life Tests. The tests predict that the working capacity (y-axis) of lithium-ion batteries (green line) will be greater over a high-mileage lifetime (x-axis) than that of nickel-metal hydride (yellow line). Past field data for nickel-metal hydride (blue dots) has shown that the testing results are conservative -- that is, batteries generally do better in the field than they do on tests. (Source: Ford Motor Co.)
Ford's confidence in the technology is real. The giant automaker had previously used nickel-metal hydride on the Ford Escape hybrid, Fusion hybrid, and even on the old Ford Ranger EV, which it produced in limited quantities in the late 1990s. In contrast, its second generation Fusion hybrid now uses lithium-ion. So does the C-Max hybrid, the Fusion Energi plug-in hybrid, the C-Max Energi plug-in hybrid, and the Focus Electric.
The key to Ford's testing effort is a lab that was part of a $135 million company investment in engineering and electric vehicle battery testing. Using a so-called Key Life Test at the battery test lab, Ford engineers believe they are able to accurately forecast the 10-year, 150,000-mile life performance of lithium-ion. To do so, they cycle batteries at the cell-level, pack-level, and vehicle-level. They cycle them in hot and cold chambers and run them on powertrain dynamometers. Using 10 months of testing, they believe they can understand how the batteries will behave at a wide range of temperatures, under various acceleration conditions, in multiple locations within the vehicle.
"Somehow, we have to take out the unused time when the customer's car is in a garage or parking lot," Anand Sankaran, Ford's chief engineer for energy storage and high-voltage systems, told us. "And then in the test cycle, we have to accelerate all the failure modes."
From prior experience with nickel-metal hydride, Ford engineers knew that their accelerated test results were conservative -- that is, their batteries actually performed better in the field than they did in Key Life Tests. Thanks to the availability of mountains of field data on nickel-metal hydride batteries with hundreds of thousands of miles, they had developed a good feel for the relationship between test and field performance. So when lithium's predicted behavior improved on that of nickel-metal hydride, the engineering team reasoned that it was time to make the switch. "At some point, you get confident and you realize that what you're doing correlates to what the customer is doing," Layden said.
Ford began rolling out several of its lithium-ion-equipped hybrids late in 2012. The company's engineers say the new breed of batteries will offer an improvement over nickel-metal hydride in a number of ways, including size, weight, fuel efficiency, and life performance.
"We know that customers will have questions about these batteries," Sankaran said. " 'Will I have to replace my battery after eight years?' 'How will lithium-ion be different than nickel-metal hydride?' Now we can provide a much more accurate picture of how it will perform."
Cap'n, this is an interesting test methodology. I understand the desire to take out the dead time in operation of a vehicle. That makes sense. I wonder if there is some effect associated with that time though. If their results with nickel-metal hydride show that real world results are better than their tests that might indicate that the time spent resting is beneficial, at least for that chemistry. It will be interesting to see what the results are for these new batteries.
No offence to FORD, but they seem silly for tested NiMH against Lithium-ion. That was already established nearly a decade ago with laptops and cell phones. Perhaps they should have tested Lithium battery types instead. Like Li-poly or Li-air.
Also, the Toyota Prius did the research for them already. Lithium-ion has been standard for some time.
Yes, we'll find out after a few years in Ford's accelerated testing results were accurate, Naperlou. I realize that accelerated test is a fact of engineering life, but I have to admit that I as a consumer am always a little bit leery of it.
The use profile of a car battery is different than that of a laptop battery. It's less predictable and the environment is more harsh. Lithium-ion EV batteries are also massive and in many cases must be liquid cooled. Finally, there's the warranty issue: Automakers need to get a good handle on useful life, especially with today's EV batteries costing $600, $700 or even $800 per kWh. Remember the dead Tesla battery of 2012? The owner ultimately received a replacement quote of $40,000.
I agree with naperlou, the testing metholdology used by Ford is an interesting one. I guess there is no foolproof way to know for sure the effect the dead time has on the battery, but it seems like they did their homework. As in most cases with technology, it's usually time that is the best test to see how long it lasts and how durable it is.
I hope that Ford does a better job of designing the battery electronics so they don't run into the dead battery pack issue like Tesla did. With Li-Ion packs the electronics will prevent the batteries from discharging to a voltage low enough to cause cell damage. They could put in a charge alarm or something simple when the battery pack gets close to this protect mode. Normally the pack will be charged from the engine (If a hybrid) but if the vehicle sits in storage for a long period of time this protect mode could cause more dead battery packs and a very disappointed customer. This is even more important in a full electric vehicle.
Choosing Li-ion instead of NiMH may make sense for durability, but recycling may be a problem. Li-ion batteries typically don't yield much return when recycled, which requires someone to foot the bill. Recycling NiMH, on the other hand, can actually pay for itself. A typical Li-ion battery has less value when recycled than a lead-acid battery. As low as one third the value in some cases. For now, I believe only one company recycles large Li-ion batteries (Toxco), which is another concern. If the value of the recovered materials decreases over time, as predicted, it may become too unprofitable to recycle Li-ion batteries, which will create a disposal problem. NiMH seems like a more responsible choice. I understand that Ford must compete with other manufacturers who have already chosen Li-ion, so time will tell if consumers care enough about recycling to have an effect.
Ford choosing Lions is going to be a tough learning for them.. if I read the news right.
It's not the chemistry alone that makes it hard to make good and reliable systems. They should actually know what they are doing. :D
If they go and compare undersized Ni-MH hybrid pack to undersized Lion hybrid pack.... what's the catch here ?
Lions suffer from heat. Cycles will not be an issue at all. Ni-MH too dies when heated (forced bad designs like in EV-1). Undersizing the pack is good way to kill cells.
Accelerated detoriation is different. There are already a lot of research done this way to determine the wearing effects on cells. But it's only part of the equation.
Having Lion EV's on roads +10 years will tell them what is actually going on. If they do not have the experience and knowledge we can already say we will not see and considerable fleet on the roads in next 5-6 years. But they have to start from somewhere. Good to know they are trying to catch up.
Instead of making all the mistakes them selves they could buy the knowledge and experiences form companies who have had Lion EVs on roads +10 years.
What it comes to recycling only copper and cobalt are recycled from Lions. With Iron phosphates the recovery percentage can be extremely good. As the only dying component is the electrolyte.
What is somewhat troubling to me is that we've been hearing for years that replacement costs for NiMH batteries would come down, drastically, but is that statement accurate if that type of battery is obsolete?
We can buy 12V lead acid batteries, anywhere because they are still being used. However, if cost is based upon high production numbers, what happens when those numbers drop, years after a "better" type of battery is invented/tested/approved?
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