6 Comments

Summary:

Many of the best practices for keeping lithium-ion batteries healthy and happy for longer in electronic devices, like laptops, can also apply to their super-sized and fast-approaching cousins: electric cars. But with cars there’s a whole lot more at stake.

You might think it’s painful to fork over $50-60 bucks for a new laptop battery or deal with a computer that refuses to hold a meaningful charge. But the pain of the dwindling capacity of batteries could be considerably greater with electric cars. Batteries for EVs can cost upwards of $10,000 apiece and a dying battery raises the prospect that you’ll get stranded somewhere miles away from a plug.

However, there are a few practices that can help lithium-ion batteries stay a little more healthy and happy. I asked battery maker A123 Systems, which started out supplying batteries for handheld power tools and is moving into the automotive and grid storage space (its batteries will be used in the upcoming Fisker Karma and electric Fiat 500), for some tips on extending battery life. Here’s three ways they offered to slow the drain.

Embrace the Middle Ground

Andy Chu, A123′s VP of marketing and communications, emphasized that in most cases drivers won’t need to “concern themselves regarding the best state of charge in which to leave their battery.” But Chu did comment that keeping a battery fully charged for an extended period of time will have “a somewhat shorter life than batteries that are held at a lower state of charge.”

That’s why some laptop manufacturers, Chu said, “actually allow users to set a lower maximum state of charge in order to extend battery life.” It’s a trade off, however, with the user choosing “slightly less runtime in exchange for longer battery life.” With certain battery chemistries for vehicles, said Chu, automakers are “using the same strategy” to extend car battery life.

According to Saul Zambrano, Director of utility PG&E’s Integrated Demand-side Management Core Products team, the gen-1 electric vehicles rolling out in the next couple years will generally have batteries limited from discharging below about 50 percent. Zambrano told us in May, that these limits on “deep discharging” are meant to “maintain battery life.”

The bottom line is that a moderate state-of-charge — in the range of 40-70 percent of capacity — is generally “the best state of charge to leave a battery before leaving [it] unused for an extended period of time,” Chu said.

Mind the Charge

Day to day, Chu recommends charging frequently, “even if it is only a partial charge.” That’s because lithium-ion batteries generally last longer when they are “cycled” (charged and discharged) “more shallowly,” rather than fully from 100 percent charge to zero.

In addition to how often you charge and how fully you let a battery discharge, how quickly you juice up a battery can also affect the rate at which it loses capacity. As HybridCars explains, 480-volt quick charging (80 percent charge in about 30 minutes) for the LEAF is expected to accelerate capacity loss compared to 220-volt charging (full charge in about 8 hours). So if quick charging is the primary method of recharging for a given vehicle, “it will bring the capacity loss closer to 70 percent after 10 years.”

Keep It Cool

A key step for maxing out battery life — whether in an electric car or a laptop — is to keep it cool. “One simple thing that a driver can do,” said Chu, “is to park the vehicle in the shade,” explaining that sunlight can create “significant increases in the cabin temperature in a vehicle,” and over time the repeated exposure to high temperatures will shrink the battery’s lifespan.

While moderately cool temperatures can help to extend battery life, true cold can spell bad news for electric range. As former GM Vice Chairman and Chevy Volt frontman Bob Lutz noted earlier this year, he only got 28 miles worth of juice from the Volt battery when he drove a pre-production version of the car for a weekend in Detroit this winter, rather than the 40 miles that GM says will be typical.

“The range can vary on any given day depending on temperature, terrain, driving conditions and so forth — especially temperature,” Lutz explained. “The distance you can go in an electric vehicle varies hugely with the outside temperature, including with the Volt.”

Image courtesy of EDF

Related content on GigaOM Pro (subscription required):

California Rules Show Opportunities in EV Charging

How to Break Into The Energy Storage Market

How EV Battery Startups Can Cross the Valley of Death

  1. Good article! Nothing like going to the source on technical subjects.

    Share
  2. If you carry around 1/3 more batteries specifying for the maximum range in order not to stress them too much in the unlikely case – this is not very efficient energy wise. It is better to change the batteries after sale if you discover that you need more endurance. This way you might also start with a much smaller pack – most people may arrange their trips minimizing length and go for rental cars otherwise.

    Share
  3. Isn’t it a bit misleading to say “Batteries for EVs can cost upwards of $10,000 apiece” when you’re citing a stat from Better Place, which does not sell its batteries? Better Place owns all the batteries it installs in EVs, which makes sense for users of its Battery Swap Stations.

    Share
  4. I’ve heard Lithium Ion batteries have a shelf life of about 5 years from date of manufacture, whether they are used or not. I hope that the people working to use them in automobiles have figured out a way around this problem, otherwise they will be too expensive to use.

    Share
  5. Tesla already does this with their batteries, they don’t charge over 90% (range mode goes to 95%) so the consumer doesn’t even have to deal with the max charge. The Chevy VOlt is even more conservative, they are only going to use about 50% of the total capacity of their battery. I haven’t heard about the Leaf charging profile, but I am sure they also will take into account these steps to extend the battery life.

    Share
  6. Bob Wallace Monday, July 12, 2010

    Range Rover is claiming a 300,000/13 year expected battery life for their 4WD SUV 200-mile-range EV Liberty.

    And a 1-3 hour recharge time.

    Way beyond anything I’ve heard any other manufacturer claim. (Except for the range.)

    http://www.telegraph.co.uk/motoring/news/7879096/Electric-4×4-to-go-into-production.html

    Share

Comments have been disabled for this post