[EMAIL PROTECTED] wrote:
> >Bear in mind that this is the same rationale for the cycle
> > life rating of PbA batteries also; end of useful life is
> > considered to be when capacity drops to 80% of rated.
>
> Actually, the manufacturers of lead-acid batteries
> often use 50% capacity as the end of the cycle life.
Optima doesn't (for EV use they spec the YT as "EV C/2 discharge to
10.5V, retaining 80% capacity"), nor does Hawker ("Hawker defines
end-of-life as the point in time at which the battery fails to deliver
a minimum of 80% of its rated capacity", "As accepted by the industry, a
battery designed for standby applications is considered to have reached
its end-of-life when it fails to deliver at least 80% of its rated
capacity", Genesis Application Manual, 5th Ed.).
Which seems to pretty much cover the PbA batteries directly relevant to
the context of this thread.
Hawker does caution that some manufacturers do use 50-60% of rated
capacity as their end-of-life criteria, however, I believe I have yet to
come across a manufacturer who states a cycle life value and doesn't
also state that the value is cycles to retention of 80% of rated
capacity.
A quick browse of Trojan's site reveals that they now only quote a
dimensionless 'lifetime energy unit' value for their product (presumably
to preclude direct comparison to competitor's product), and no
indication of what the end-of-life criteria might be. However, if I
recall correctly, the Trojan plots in Bob Brandt's book did indicate
that Trojan uses (or used to use) 80% as their end-of-life criteria. US
Battery's site simply states that it is impossible to quote a meaningful
cycle life value since it will vary from application to application
depending on how the battery is treated, etc. and leaves it at that.
What PbA manufacturers have you encountered who use an end-of-life
criteria other than retaining 80% of rated capacity for EV-relevant
products?
Cheers,
Roger.
