Re: Li-Ion life cycle management

On Thu, 22 May 2008 10:21:44 -0700 (PDT), Richard Henry <pomerado@xxxxxxxxxxx>
wrote:

On May 22, 9:56 am, Joerg <notthisjoerg...@xxxxxxxxxxxxxxxxxxxxx>
wrote:
rebel wrote:
On Wed, 21 May 2008 13:08:58 -0700, Joerg
<notthisjoerg...@xxxxxxxxxxxxxxxxxxxxx> wrote:

That might not be a cost effective application for Li-Ion. Isn't their
self discharge alone a few percent per month?

No, our measurements place it around 0.1%/month.

Well, the data from Henry's link states "Self Discharge: < 4 % per
Month". Quite a lot, actually. But he wrote that they'll be charged
right before the event, so should not be a problem. Lack of storage
capacity after a few year will be, though.

My experience with rechargeables is that there will be a reduction in
capacity after many cycles (~hundreds). Is there a similar decline in
capacity over time if they are not used much?

I have here a Li-Ion pack in an Acer (AcerNote Lite 370) laptop which is
date-stamped week 37, 1996. It still delivers about 2/3rds of its initial
run-time. What it DOESN'T do is live in the machine when AC power is used.

Considering the low number of cycles that your application is likely to rack up
in say ten years (6 cycles per exercise x N exercises per year x 10 years) the
deterioration will largely come from (a) initial build quality issues and (b)
temperature issues. Temperature as the one you can control to some extent.

The effect is most probably best considered as the cumulative effect of elevated
temp x time at elevated temp, If your storage temperature is sane (as is the
case with my OLD Acer pack) I wouldn't foresee a dramatic capacity loss.
.

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