Lithium-ion batteries -- there are different chemistries, and they are very
different -- may not be a universal answer for EVs. Right now there appears
to be is a major problem with the LEAF's battery rapidly loosing capacity in
high ambient temp environments as reported at myNissanLEAF-com.
The situation is narrowly focused -- for now at least -- because it involves a
single brand of car, the LEAF,;a single lithium-ion chemistry, IIRC lithium-
manganese , LiMn2o4?; with a simple Temperature Management System, air,
only when the car is charging or operating; and a limited geographic area,
AZ, or more properly Phoenix.
LEAFs there, essentially all of the MyNissanLeaf owners in Phoenix, have seen
a significant and they believe accelerated loss of HV battery capacity. The
loss appears to be independent of all operation variables: battery charging,
miles accumulated, car color, etc. Apparently the only common condition is
just being in the extended, routinely in excess of 100 degF, summer temps in
Phoenix. Owners have seen capacity losses of up to 20%, with a few saying
that another 6% hit is only a matter of time, and that very short as the REAL
summer temps are only just beginning.
The heat is baking the capacity out of the HV batteries. And there's nothing
that can be done. Charging times, charger type, voltage are all irrelevant.
Right now, LEAF owners in Phoenix are in what I'd call a "capacity
preservation" mode. This consists of daily charging only enough to meet that
days needs - charging to 100% is not recommended high heat or no, charging
at the coolest part of the day -- but even overnight the ambient temp often
doesn't go below 85 degF, centering charge around 50% -- which results in
more frequent L2 charging at public chargers. They're not looking for
extended range per se, they're looking to minimize the amount of charge
delta at any single charging.
There is a very small chance that the capacity reduction is the result of a
pre-programmed Battery Management System strategy to protect the HV
battery. And maybe, just maybe there's a l-o-n-g, outside chance that some
capacity will be regained in cooler weather… in the fall, 3 long, hot months in
the future.
The interesting thing is the LEAF folks can measure their HV battery capacity
every time they charge up. Some knew, or suspected, that something was
happening long before the community as a whole accepted it.
The simplest lesson learned is, thermally speaking, treat your HV battery
with kid gloves… no matter what battery chemistry you have. Keep it cool.
If the heat bothers you, it bothers your HV battery too. You my be able to
retreat to a pre-cooled house at the end of your trip, but your car/HV battery
will continue to cook, long into the night in some cases.
Park in the shade, use windshield/rear hatch sun shades. If possible, leave
windows open an inch or two.For those of us driving Prii, the HV battery is
cooled with cabin air. On hot days forget max MPGs, use the air cond, you'll
fell better, and you battery won't be stressed. If the HV battery fan comes on
before the air cond, you screwed up.
A relevant read:
Warranty Implications For BEV AndStart-Stop Vehicles