Li-Ion batteries decline in capacity at a steady slow rate, until they
eventually have zero capacity. Pretty much a flat curve. (Actually
slightly concave. They decline slightly less per cycle as they age.)
Lead-acid batteries "fall off of a cliff" at their end of life. They
rise slightly in capacity on the first few cycles, then steadily decline
to about 3/4 of their rated capacity. After that, they are in a death
spiral and fall to near zero capacity after a short while.
Big difference. This is why Li_ion EV packs have a promising secondary
market. They are still fine, but simply have reduced capacity. Reduced
range in a car, but useful for stationary applications or other
applications where half the energy per kg is not a problem.
Makes for an interesting used car market. Only need to go half as far?
Buy a used EV far a bargain. Retired folks that simply need to drive
back and forth on short errands are a great market for EVs with "run
out" batteries.
Also, replacement li-ion batteries are getting cheap. Approaching $100
per kw-hr these days.
Bill D.
With a lead battery, 68% of factory specified capacity would be considered a
fully depreciated battery, ready for replacement. Actually anything below
80% would be.
Is this not the case with lithium? Is a lithium battery with 68% of spec
capacity still considered usable?
David Roden - Akron, Ohio, USA
EVDL Administrator
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