Michael Ross wrote:
> Even though marketing likes accelerated life testing, and it
> gives a higher comfort level to everyone, accelerated life
> testing can just take resources away from more serious
> This is where the work at Dalhousie got its motivation.
> Their approach was to jump up the accuracy of testing by orders of
> magnitude. In a nutshell they built top of the line test
> equipment using very high quality current sources, they performed testing
> in thermal chambers maintaining extremely steady, elevated temperatures,
> and so on, all to reduce environmental and measurement noise and
> uncertainty. Through these means they were able to detect very small
> levels of cell deterioration and malfunction, while NOT cycling the
> cells; instead simply maintaining the damaging conditions and
> stopping occasionally to examine cell function (capacity, resistance,
> etc.), the test periods were drastically reduced from accelerated life
> testing protocols.
First of all, what you describe *is* accelerated life testing, whether the
cells are being cycled or not.
Secondly, you are mistaken about the not cycling part; the presentation that
Dr. Dahn gave at AABC a few years ago describing the high precision test
equipment they had designed and how it was being used specifically stated that
the purpose of the high precision equipment was to allow the measurement of the
(hopefully ;^) very small amounts of capacity loss that results each time the
cell is *cycled*. Since the capacity loss is (supposedly) linear with the
number of cycles, the higher precision test equipment allowed them to determine
the rate of capacity loss while performing much fewer cycles than had
traditionally been required, and it was then possible to extrapolate from the
measured capacity loss per cycle to predict the cell cycle life to whatever
residual capacity level one wanted.
He may certainly have moved to the test regime you describe in more recent
times, however this was not the original intent behind the development of the
high precision test equipment.
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