Navigant Research Blog

Lithium Ion Batteries Can’t Stand the Heat

— June 22, 2012

Lithium ion batteries are truly fair weather friends – just like people, they fare best in a comfortable climate.  Lately, we at Pike Research have been delving deep into how environmental factors, such as temperature, affect battery performance and the rates at which vehicles are charged or discharged.  Our discussions with automotive companies and battery pack assembly companies have revealed numerous approaches for optimizing performance and extending a battery’s life – comparable to the many ways people dress to beat extreme heat.

According to our research, lithium ion batteries perform optimally, and will last longer, if they are kept at temperatures between -10°C and +30°C.  This range is consistent with findings by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE).

In very cold temperatures, batteries don’t achieve their full rated power until the battery cells warm up.  According to Ford engineers V. Anand Sankaran and Bob Taenaka, this short-term effect has greater implications for battery electric vehicles (BEVs) than for plug-in hybrids (PHEVs).  A PHEV can rely on its gas engine for power during warm up, but BEVs don’t have that other power source.

As the accompanying EERE graphic shows, batteries exposed to hotter average temperatures lose their ability to store energy; the hotter the temperature the faster they lose their storing ability.  So BEV owners in Phoenix will likely be looking to replace their batteries faster than owners living where the thermometer doesn’t often reach 110°F.

To combat the extreme temperature effect and keep batteries within their optimal temperature range, automakers use thermal management systems relying on either air or liquid cooling.  As the EERE data shows, liquid cooling is generally more likely to preserve a battery’s capacity than air cooling, though performance variations will occur depending on how well a battery management system was designed to control temperature.  According to Ford, the liquids used in cooling systems can retain a temperature for a long time, which contributed to Ford’s decision to use liquid cooling on the Ford Focus EV.  Ford has also used air cooling on its hybrid Escape and Fusion, as have Nissan and other BEV manufacturers on their vehicles.

In addition to external heat potentially shortening the usable life of a battery, operating batteries at high charge and discharge rates can have another negative impact.  That is particularly true for fast DC charging a battery pack at a rate of 50 kW for as little as 30 minutes (the expected time to charge a BEV 80%).  If done every day, that would generate enough heat to reduce the battery’s capacity.  BEVs that offer fast charging were designed with this fact in mind, so their battery management systems can force an EV charging system to slow down, thus protecting the batteries well before the pack is fully charged.

The interaction of batteries and fast charging is one of the many EV topics that Pike Research will explore at the Plug-In 2012 conference, the premier North American EV industry event, on July 23, 2012, in San Antonio.  I’ll be representing Pike Research at the conference where Ford and many of the leading companies will be discussing business models, technology challenges, and EV rollout strategies.


Tesla, the Darling First Child

— June 21, 2012

Though many startup companies in the electric vehicle (EV) industry have either struggled to survive produce a profit, or insure investors of their products’ worth (or all three), one company has consistently bucked the trend of disappointing news: Tesla Motors.  In 2008, the company first began selling its first-generation all electric Tesla Roadster and since then has placed more than 2,000 of the high end EVs worldwide.  The Roadster is largely credited for restarting the EV revolution, and since its debut, no other manufacturer has been able to replicate a model with similar electric range and style.

The company struggled to make its first deliveries, but has largely overcome its early production troubles.  By all accounts, it is not just surviving; it’s thriving.  Recent news items include preorders of next year’s Model X all-electric crossover, netting the company more than $40 million overnight.  In other company news, Tesla will begin repaying $465 million to the U.S. Department of Energy (DOE) in December and has decided to begin deliveries of its more than 10,000 reserved Model S sedans one month earlier than previously forecasted.

Amid this good news, don’t forget that Tesla has never made a profit and by some current estimates, its 2Q 2012 will be its most unprofitable quarter since it went public in 2010.  However, starting a car company from scratch requires an enormous investment, and Tesla is not anticipated to earn a profit until 2Q 2013.

Having an estimated date for profitability is more than quite a few upstart EV makers and their upstart suppliers can boast.  No doubt, the promise of profitability is making Tesla attractive to investors.  Bursting Tesla’s balloon a bit, John Petersen, in a guest post on Greentech Media, describes the company’s growing popularity in the last 2 years as part of a “hype cycle,” in which interest in a company grows before an event and recedes afterwards.  For Tesla, the Model S may be that event.

Or, it may not be for two important reasons: 1) Tesla is the darling first child of the EV revolution and 2) the company continues to push the EV envelope.  People like the underdog, and despite being the first child, Tesla has kept the underdog image as the big auto makers, GM, Nissan, and Toyota, have crept into the company’s EV space.  The Model S may also be considered the company’s equivalent of Apple’s iPhone 4s, and the Model X (due out in 2013) would be the iPhone 5; meaning the hype is not going away with the Model S.

Tesla’s Model S deliveries begin on June 22.  As is customary with Tesla, a great deal of publicity has surrounded the event and the company has even put a ticker on its website, counting down the seconds to the moment that CEO Elon Musk will hand deliver the keys to the first owners.  The magnitude of this fanfare and its fan following is not uncommon among new PEVs, but it isn’t the end of the Tesla hype machine.  Let’s hope the Model S delivers on all its grand expectations, but let’s also be mindful that this is only one of potentially many new models to be delivered by the darling first child.


Making Sense of California’s Zero Emissions Vehicle Program

— June 10, 2012

For the past two years, electric vehicles (EVs) have been prominent subjects of automotive news pages, with OEMs introducing new models almost monthly.  The latest announcement is the Toyota Rav4 EV, which is scheduled to hit California dealers late this summer.  The Rav4 really exemplifies most of the EV announcements because it, like many of the EVs, will first be available in California and it will be sold in limited numbers.

This type of vehicle has been called the “compliance” EV; its main purpose is not to capitalize on the demand for EVs but rather to comply with California’s Zero Emissions Vehicle (ZEV) program, in which 10 other states participate.  Other compliance EVs are the Chevrolet Spark EV, the Honda Fit EV, and the Ford Focus Electric.  Vehicles designed specifically for compliance should not be that surprising since the first major OEM-produced ZEV, the GM EV1, was a “compliance” vehicle for the 1996 version of the California ZEV program.  Since the ZEV program has proven a major influence on the EV industry, we should examine it in greater detail to better understand and anticipate the strategy behind the way OEMs are introducing their plug-ins.

The ZEV program, which is run under the greater Advanced Clean Cars (ACC) program adopted by the California Air Resource Board (CARB), is a mandate requiring OEMs to deliver a minimum percentage of Partial ZEVs and full ZEVs to California annually.  Partial ZEVs (PZEVs) are Plug-in Hybrids, Hybrids, and low emissions conventional vehicles.  The program specifically targets large (60,000+ CA sales/annually) and intermediate (4,500-60,000 CA sales/annually) volume OEMs.  Any OEM with less than 4,500 is not regulated, but can still participate in trading credits; Tesla, Phoenix, and Zip Car do this.  (Although Zip Car is not an OEM, it participates through various allowances and exceptions within the program rules.)

Large volume OEMs like GM, Nissan, Ford, and Toyota must follow the most stringent ZEV requirements, supplying at a minimum 7.6% of their 2012 requirement (12% ZEVs) through actual ZEV credits. That works out to just under 1% of actual fleet sales.  Intermediate volume OEMs like BMW, Kia, Volkswagen, and Volvo can fulfill their entire requirement through PZEVs.  For 2012 through 2014, ZEVs must make up 12% of OEMs deliveries; from 2015 through 2017 they must make-up 14%; and after 2018, they must comprise 16%.

The program is administered using credits to determine the total value of OEM efforts that comply with the program.  So, pure ZEV deliveries accrue more credits for their makers than the more basic PZEVs do.  In this system one credit is equal to the base level ZEV.  A delivery of the most basic PZEV to California earns its manufacturer 0.2 credits, no further credits are bestowed on the manufacturer once the vehicle has been placed into production.  Neighborhood electric vehicles (NEV), and Compressed Natural Gas (CNG) vehicles also receive credits.

Credit values for each model vary as there are many additions, multipliers, and classifications awarded vehicles for a wide range of characteristics, including the use of advanced components, use in a public transportation system, and an all-electric range.  For example, a ZEV with an all-electric range of 300+ miles and fast refueling capabilities (hydrogen) can earn over 7 credits.  If an OEM accrues extra credits it can save or trade the credits with other OEMs.  The financial penalty for not meeting the requirement is $5,000 per ZEV (or credit); there is no defined price for the credit, so we can assume the traded value for a credit does not exceed $5,000.  In 2011 there were four total trades, the biggest being a trade of just under 23 credits from Tesla to Honda.

Basic ZEV Credit Ratings

  2012-2014 All electric Range
Type 0 1 Default Case
Type 1 2 50-75 mi range
Type 1.5 2.5 75-100 mi range
Type 2 3 100+ mi range
Type 3 4 100+ FR/200+ mi range
Type 4 5 200+ mi range FR*
Type 5 7 300+ mi range FR*









*FR = Fast Refueling

Determining the credit amount for each specific technical advancement in emissions reductions technologies is one of the most important pieces of this program.  It is especially important for smaller OEMs like Tesla, Phoenix, and Zip Car, which are not regulated under the scheme, but can still profit from it by trading credits they accrue with OEMs that cannot comply on their own.  So, specific credit ratings bestowed on specific fuels or technologies can influence the direction of technological development within the industry.

An example of this influence is the new set of standards adopted in January 2012 for the years 2015 through 2025.  The new standards introduce the BEVx credit, which is used for full electric vehicles with small back up engines to extend the EV ranges in low charge situations.  Also within the new standards are requirements placed on fuel suppliers (BP, Chevron, Tesoro, etc.) to deliver cleaner fuels as part of ARB’s Clean Fuels Outlet (CFO) program.  These regulations focus particularly on hydrogen; CARB forecasts having 50 commercial stations in operation by 2025.

Many of the OEM-announced EV introductions are “compliance” vehicles and may never enter markets outside of California, but that fact should not discount the tremendous impact the ZEV program has had on the greater auto industry.  As of January 2012, 2.16 million PZEVs and ZEVs have been produced for California.  Based on the increased standards CARB introduced in January, CARB forecasts that by 2025, just under 250,000 ZEVs and PHEVs will be produced for the California market annually, or 15.4% of California’s new vehicles.  While credit for the EV revolution cannot rest entirely on the ZEV program, it deserves recognition for advancing fuel efficient technologies and helping reduce the prohibitive cost of EVs so that someday, people in other states can own a similar vehicle.


Green and Clean Port Policies

— June 10, 2012

The idea of clean waterways is nothing new; however, in the past few years, several major ports have been getting special attention for their “green port” initiatives.  Since ports are densely-constructed economic zones bustling with fleets and major infrastructure, characterizing them as cities unto themselves is appropriate.  And, these cities are now going green.

Frequently ports are far removed from urban centers, so it’s difficult to appreciate the scale of their activity.  The busiest port in the world, in terms of numbers of containers, is Shanghai.  In 2011, 31,739,000 twenty-foot containers traveled through there.  While most of the world’s busiest ports are in Asia (mainly in China, Singapore, and South Korea), also ranking in the top 20 are Dubai, Rotterdam, Hamburg, Antwerp, Los Angeles, Long Beach, and Bremen.

Following this trend, the port of Long Beach is implementing a Green Port Policy that targets improvements in wildlife, air quality, water quality, and soil in the port area.  The Pacific Coast Collaborative is spearheading an even broader initiative to improve green practices at ports from Alaska to California.

Why are green ports an important cleantech trend?  Ports are closed systems.  Although vehicles (trains, trucks, ships) carry goods away from ports, the fleets and activities at a port itself remain within a fixed area.  This makes them ideal for alternative fuel fleets because infrastructure can be installed at a few key sites in a port and then entire fleets can be fuelled.

Ports also run 24 hours a day, so they are well-suited for distributed generation, especially technologies that run best at a constant rate of output, such as fuel cells.  But why stop there?  Distributed solar, green building technologies, energy storage, and microgrids would also be well-suited to ports.


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