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."
Not to go overboard in the use of industry jargon, but the technical description of that scenario is that "the customer is screwed."
On the plus side, aftermarket companies will in all likelihood jump in and offer conversion packages to enable owners to replace their old battery packs with the better technology. It's like converting an old pre-'80s car with a breaker-points ignition system to capacitive discharge (electronic) ignition.
I fear resources needed to create the Li-on batteries will start to become scarce, as more and more devices use them. Start manufacturing 700 pound versions of them will only hasten the demise. I would like to see Ford and Toyota look into alternative battery types, or even supercapacitors. I think supercaps will end up powering our devices in the near future, not sure about cars though. Caps can charge fully in a few minutes as opposed to hours.
My bet is that the Ford engineers know more than they are telling. In the past few years I have observed that company to be doing a whole lot of really intense research in a variety of areas. So without giving away any of their secrets, I can offer that they do know what they are doing, but you will not get them to explain it. The rest of their secrets will need to come from their internal publicity group, I said all that I can disclose.
It's amazing no one bother to mention the small fact that Chevron who owns the NiMH patents won't let anyone build them over 10amphr and they do not play well together in parallel so no one can build EV's with them.
So in reality Ford, others if they want any kind of range have to go to Lithium batts. Now add Lithium actaully costs less than NiMh batts do mow plus NiMH uses Rare earth's that China is restricting exports on puts the nail in the coffin for them.
But the Chevron NiMH patent runs out soon but won't matter as Lithium has so surpassed them in every way from capacity, weight, impulse power and range.
And to the poster who thought Li materials are rare and short supply is completely wrong as cars already use the same materials except possibly Lithium which is not expensive or rare, in fact quite abundant.
The latest Mazda 6 uses a supercapacitor system, called i-ELOOP.
"When a car equipped with i-ELOOP is decelerating, a variable-voltage alternator (12 to 25 volts) pumps electricity into an electric double-layer capacitor (also known as a supercapacitor). When the car comes to a stop, Mazda's engine stop-start system—branded i-stop—takes over and shuts the engine off. At this point, all auxiliary vehicle functions (radio, HVAC, headlights, etc.,) are powered by the supercapacitor; its 25-volt output is stepped down to 12 volts by a DC/DC converter. There are times that the supercapacitor will recharge the 12-volt battery, too."
Good point, Jerry. Definitely worth mentioning. It should also be noted, however, that Ford is using lithium-ion across the board, including in the second-gen Fusion hybrid and the C-Max Energi hybrid -- both of which use smaller batteries that would be unaffected by the Chevron 10Ah patent encumbrance. Ford told us they chose lithium-ion because it's "smaller, lighter weight and (has) better re-charging capability." And (this is what the article was all about) their testing capabilities gave Ford engineers confidence that lithium-ion would be more durable than NiMH.
I agree with Ford NiMH never was that good a battery and Lithiums have left it in the dustbin of history mostly because of it's more costly material and the fact that they need 3x's the cells because they are only 1.2vdc/cell.
On the post above supercaps won't ever be viable as they cost way, way too much for the pitiful capacity they have. Just do the numbers on them and it quickly become painfully clear.
Charles, do you happen to know if these batteries are standard in any way or are they built specifically for Ford? I know that they are suppose to last for pretty much the life of the car - at least the first owner, but it would interesting to see what happens after that.
Charles--very informative. I don't know that much about batteries but, is "working performance" (y-axis) the same as cold-cranking amps? I am assuming that's the case. If so, I can see how HALT (highly accelerated Life Testing) under hot and cold conditions, could bring about the conclusions you mention. I do have some experience with running components using powertrain dynamometers and the results for the equipment we tested were basically the same as actual "road tests". Again, very good update.
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