From: Tim Ikeda (tikeda_at_sprintmail.com)
Date: Thu Mar 22 2001 - 21:08:25 EST
Donald MacQueen <dmacq_at_erols.com> asked:
[...]
>why do they put counters on batteries? planned obsolescence?
Probably not, but I've never worked with marketing types so
I can't claim to know how they really operate ;^)
Batteries could use counters for making better estimates for "fuel
gauges" (the amount of charge remaining). Counters might also be
used to determine when to recondition a battery or to change
charging methods as the battery ages. So they may actually be used
to increase a battery's performance and life span.
Dallas Semiconductor markets these as "Battery Identification
Chips". The information they carry can be read by the computer
to determine what type of battery pack was inserted. The computer
can then adjust fuel gauges & charging methods and even manage
power use as appropriate for the battery.
I'm going to take a SWAG (sophisticated, wild-assed guess)
that the problem Sven sees -- with his battery pack that isn't
recognized by the 701C -- is due to a damaged DS2324 chip or
corrupted data in its memory (Assuming the problem is confined
to that single battery pack).
Some of the chips offered by Dallas measure temperature, voltage,
current and time. That should make it possible to determine the
amount of life and charge time remaining for a pack with a pretty
good degree of accuracy. The chip I found in my NiCad pack isn't
so sophisticated: some RAM, non-volatile memory and a thermometer.
The thermometer helps with setting the optimum charging rates.
The chips has three pins: for BAT-, VDD and data I/O. If I'm reading
the spec sheets correctly, you should only need to connect to the
BAT- and DataI/O to converse with the chip.
Also according to the spec sheet, there are portions of the chip's
memory address space which can be locked, like the cycle counter,
but it's reversible. In principle at least, it may be possible
to reset a battery pack or take a pack that once had NiCads
and rebuild it with NiMH cells. Given the current price of
new batteries for 701s vs. replacement cells and time spent
futzing with a spent pack, it doesn't make a lot of economic sense
to rebuild them. This will change in a couple more years when the
supply of working packs vanishes. But it always makes sense if it's
fun (YMMV). And in Sven's case, if the chip wasn't blasted by static
and only needs to be reset, then it's a bargain.
*** Note to Sven: If you've got a power supply and can monitor the
DataI/O line with an oscilloscope, it should be relatively easy
to tell if the chip is still alive. It responds to a "reset
pulse" with a delayed "presence pulse" of its own. See pp.12-14
of the DS2434 description at:
http://www.dalsemi.com/datasheets/pdfs/2434.pdf
For reference, the contacts on the outside of the battery
are (w/ the label-side up):
*flatter-edge* [ + ] [VDD] [DIO] [ - ] *rounded-edge*
Regards,
Tim Ikeda
tikeda_at_sprintmail.com
PS: Found an interesting description of the Dallas 1-wire
protocol (power and data are carried on the same line).
It's a two-part article by Jeff Bachiochi at the Circuit
Cellar website (w/ links to .pdf versions of the articles):
www.edtn.com/embapps/emba050.htm
www.edtn.com/embapps/emba056.htm
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