Recipe for Li-Ion battery longevity
Mikkel L. Ellertson
mikkel at infinity-ltd.com
Tue Mar 20 16:15:38 UTC 2007
Aaron Konstam wrote:
>
> The issue I think is this. Some types of batteries have memory in the
> sense if you change them when they are half charged they will henceforth
> only discharge halfway. Batteries generally put in laptops and cell
> phones (LI-Ion) this fault as far as I know and therefore they can be
> discharged and charged at will. Also it is my belief that the circuitry
> in these devices will not allow over charging.
>
Most laptop batteries have a small circuit built into them that
keeps tract of battery usage. This is what reports the charge state
of the battery. It recalibrates when you do a full charge/discharge
cycle. (Full discharge being when the battery voltage starts to
drop.) This is necessary because the voltage output on LI-Ion
batteries remains constant for most of the discharge cycle. This
circuit usually also controls the charging of the battery.
One interesting aspect of this is that if you repair a battery by
replacing cells, you have to reset the circuit to restore full
charge/discharge performance. (There is Linux software to do
this...) Depending on the circuit, you can also run into problems if
you let the battery go completely dead - you may not be able to
charge the battery without opening it up, and putting in a small
charge to power the circuit. I am not sure why some appear to be
designed to only be powered from the battery, and block incoming
power from the charging source when the battery is dead...
Mikkel
--
Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!
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