Re: Li-Ion life cycle management

On May 20, 6:23 pm, rebel <m...@xxxxxxxxxxx> wrote:
On Tue, 20 May 2008 07:20:18 -0700 (PDT), Richard Henry <pomer...@xxxxxxxxxxx>
wrote:

Any advice on extending the life of Li-ion rechargeable batteries?  Do
they work better if deep cyled (discharged, then charged)

NO, absolutely not.  That is literally throwing away useful cycle life.

or kept close to topped off as much as possible?

The factors that cause deterioration in Li-Ion cells are heat, terminal voltage,
use - not necesarily in that order..

Depending on whether your longevity is to be considered in cycles or years, and
whether this is used regularly/intermittently/infrequenctly/rarely the tradeoffs
may well be different.  There is no free lunch in sight, only compromises that
may or may not suit your objective(s).

For maximised "storage" life, I would aim to keep the cell(s) around the 40-60%
state of charge, and cool without being paranoid about the latter.  The higher
the maintained cell voltage, the higher the rate of deterioration.  Ditto higher
temperature, but trying to beat room temp generally isn't worth the effort..

For a cell/battery in semi-regular use the cycle life can be improved by
reducing the charge voltage if this is under your control.  Dropping to 4v1 from
the more typical 4v2 will probably double the cycle life while reducing
available capacity by something like 20% or less.  Unfortunately appliances (eg
laptops) don't give you that option, but packs using discrete chargers may do so
either directly or indirectly.

And in regard to temperature ...
Considerable heat is generated in laptops, and manufacturers go to great pains
to try and keep the battery away from it.  Most do a fair job, but there isn't
enough freedom in the design of ever-more-powerful-and-compact machines to avoid
a temperature rise in the battery pack from adjacent hardware. So if you are a
daily laptop user and operating from a wall supply, the single biggest factor
you can control is the battery temperature.  Once it has charged sufficiently
for your next period of dependency, pull the battery out of the machine.

My application will likely be the following: equipment stored for
months, then broken out and set up for a 5-day exercise. During the
exercise, battery packs will be swapped out as needed, but the user
prefers that the swap times be at least 12 hours apart. The batteries
are combined in tactical packages whose nominal voltage is a around
12-15 volts.

http://www.ultralifebatteries.com/data***.php?ID=UBBL06

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