Saturday, July 06, 2013

Nissan Leaf Battery Capacity Loss

A method of estimating the likelihood of your Leaf experiencing temperature related accelerated battery capacity loss:
  • If you almost always see five bars or less on the battery temperature gauge, and it only gets up to six bars a handful of times each summer... Don't worry about it.
  • If you see five bars or less during the winter half of the year, and fairly often see six bars during the summer half... You probably are going to see the loss claimed by Nissan (20% loss at 5 years and 30% loss at 10 years).
  • If seeing six bars is common for a large part of the year, and a seventh bar pops up occasionally during the summer months... Consider leasing instead of buying the Leaf
  • If you spend a large part of the summer with seven temperature bars or more showing... It's probably best to avoid the Leaf completely. Consider an EV with an active thermal management system or the Chevy Volt.
For those that already own a Leaf, there are a few things you can do to minimize battery capacity loss:
  • Keep the state of charge in the 30-40% range (on the Gid meter) as much of the time as reasonably possible. This roughly corresponds to 3-4 fuel bars for a new Leaf. Charge to 80% or 100% right before you need to make a longer drive.
  • Shallower cycling (DOD) of the battery pack when possible. For example, two cycles of 60% to 30% SOC rather than one cycle of 90% to 30% should be better for the battery pack.
  • Avoid parking in the sun when possible. Solar loading may increase the yearly average battery temperature by 1.3-3.1 degrees Celsius for a vehicle always parked in the sun.
  • Drive and accelerate more slowly and more efficiently. This will have two effects:
  • Minimizing waste heat (estimated to be 1% at 10 KW power draw, 3% at 30 KW power draw) 

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