Posted by ASAAR on 10/31/06 21:38

On Tue, 31 Oct 2006 13:02:17 -0500, Joel wrote:

>> I'm really puzzled as to what is the purpose of this battery. Is it
>> used for anything important in the player or is it just built to make
>> sure that once the battery is dead, you have to buy a new player?
>
> I suppose it might keep the clock setting if the main battery is
> removed, or something, but that's still not anything vital, since you
> were able to get it working again. I'd say you're probably right
> about the real reason it's there.

It could also be used to maintain user settings if they're stored
in CMOS RAM instead of the flash memory used by many mp3 players.
Some clock/calendar chips also include a small amount of scratchpad
CMOS memory. The battery was probably defective, and was expected
to last much longer than most people would use the mp3 player before
upgrading. Lithium button cell batteries for this purpose often are
good for 10 years or longer. It could also be a small rechargeable
battery. Some camera manufacturers (Sony for one) use this method,
where the main battery constantly trickle charges the soldered
internal battery. If the main battery dies, the internal battery
keeps settings from being lost for about a month or so. As it would
be very simple to use a small long lived capacitor instead, the use
of the battery may well be a manufacturer's knee-jerk adoption of
the planned obsolescence that they figure to be in their $ interest.

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