Rule for EV Battery Health: Location, Location, Location

By · April 18, 2013

UK Nissan Leaf

Never mind frequent rapid charging and high mileage, the U.K. climate is kind to the Nissan LEAF's battery pack.

In late March, 2011, I was one of the first people in the U.K. to spend hard-earned cash on a 2011 Nissan LEAF. Since then, my EV has covered nearly 35,000 miles, had two services, a new set of tires, and been all over the country.

Thanks to obsessive-compulsive note-keeping, I know when my LEAF was serviced, what was done when, and how much it cost. I even know when it returned to the dealer for official Nissan recall work.

The thing I haven’t known—until recently that is—is the health of my car’s battery pack.  How much capacity has my LEAF’s battery pack lost after two years of weekend shopping trips, family vacations, daily commutes and more rapid charging sessions than I care to remember?

Thanks to my friend Mark—whose partner made a DIY variant on the GID-meter so popular with LEAF owners worldwide—I can now say that my car has lost a scant 1 percent of its original battery capacity.

Looking at the GID

In 2011, a clever California-based LEAF owner by the name of Gary Giddings discovered that his LEAF was transmitting a numerical value over its diagnostic port which turned out to be the real available battery pack capacity in watt-hours divided by 80. The LEAF community duly named the unit a GID in his honor.

In a brand new LEAF, the number of GIDs displayed by a GID meter is 282, the equivalent of 22.56 kilowatt-hours. When fully charged, my LEAF reported a total of 278 GIDs, the equivalent of 22.24 kilowatt-hours of stored energy.

Take one from the other, and you’re given a true figure of the capacity loss due to aging. The answer? Just 0.32 kilowatt-hours, or a little less than 1 percent.

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Home-made GID Meter reports a healthy battery pack.

It's About Location

My LEAF has been driven hard. It’s been rapid-charged more often than most U.S. Leafs because we have many more rapid chargers in the U.K. than there are in any one state in America. So why is its battery pack so healthy? Location, location, location.

The past few summers in the U.K. have been cold by British standards. With an average temperature no more than 60 degrees, we’ve seen temperatures peak occasionally in the high 70s.  In other words, very much like the Pacific Northwest.

This contrasts dramatically with cities like Phoenix, Arizona, where summer temperatures stay in triple-digits for extended periods of time. Like a plant without water, LEAF battery packs really do wilt in extreme temperatures. Prolonged exposure to high heat, and battery life is dramatically reduced.

Battery Tips

But while those of us in colder states and colder countries can rest assured that our LEAF battery packs will likely outlast our cars, what can those in warmer places do to keep their battery pack healthy?

  • Park out of direct sunlight, where it’s cooler. That way, your battery pack won’t be roasted alive. Wherever possible, park in an air-conditioned garage or consider buying a portable air conditioner for your home garage.
  • Avoid making your LEAF’s battery work hard in extreme heat. The harder you drive, the harder the battery pack has to work. The same goes for charging: Level 1 charging at 110V is much kinder to the pack than faster charging rates.
  • Keep your LEAF’s battery in the safe middle-ground between 20 percent full and 80 percent full. Below 20 percent and above 80 percent, your LEAF’s battery will quickly heat up if asked to do any work. This also means charging to 80 percent instead of 100 percent.
  • Invest in a GID meter, so you can monitor the capacity of your pack over time.

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