[Thinkpad] TP600 Battery Pack problem

[David Gemmell - VK4GL]

Hi Steve,

That's the most lucid reply I've ever seen on a newsgroup / mail-list.
That's saved a heap of my time.
Thank you - you've made my day !

Continuing then ...
If IBM counts charge cycles, is it then the case that
replacing single batteries in a used battery pack
is a total waste of time?

If the the micro-controller has reached it's
max-recharge-count and shut down further
charge cycles, putting a new battery (or batteries)
in the pack will achieve nothing ??

Is this what happens ?

Now that's REALLY planned obsolescence !

And I'll bet there's no way of resetting the counter ?

How Cool !  Next we'll have cars that have a
max-start-counter and can never be started again ... :-)

Cheers

David

----- Original Message -----
From: "Steve Carter" <scarter at vcnet.com>
To: <thinkpad at stderr.org>
Sent: 05 December, 2003 5:32 AM
Subject: Re: [Thinkpad] TP600 Battery Pack problem


>
> The built-in smart charger for the TP600 battery pack
> appears to be a fairly sophisticated microprocessor-based
> controller.  You can see the crystal in several of the photos.
> One of the surface-mount ICs appears to be a micro-controller,
> and there are a lot of other supporting integrated circuits.
>
> The problem they (IBM) are trying to solve is that in any series
> battery, some cells age faster than others. The hottest ones
> presumably age more rapidly, as James pointed out.  But they
> all age, even when not being used -- especially Li-Ion cells.
>
> At the end of useful battery life, the cells that have lost the
> most capacity (i.e. aged the fastest) become overcharged when
> trying to charge the remaining cells -- they're all in series
> and the same charge current flows through each cell.
>
> But here's the catch:
>
> Li-Ion cells can and have explode(d) when overcharged.  It seems that
> they when overcharged they evolve metallic Lithium, which is hugely
> reactive, and this results in a spontaneous reaction, or explosion,
> euphemistically called "venting with flame" by the cell manufacturers.
>
> On the NASA's Mars Rovers, which have 8 Lithium-Ion cells in series (!),
> the design team created eight individual battery-bypass circuits to
prevent
> weak cells from being overcharged.  Hopefully this technique will extend
> the life of the battery packs, since there is no opportunity to replace
> the cells once launched.  The Maytag repairman doesn't make house-calls
> to deep space.   :-)
>
> It seems unlikely that IBM went to this extreme in the design of their
> battery pack for the TP600 series.  What the word-of-mouth evidence
> seems to indicate is that after, perhaps 300, full (~80%) discharges the
> charging circuit is deliberately disabled to prevent a liability
situation.
> IBM is often said to be a company run by lawyers, as you may have heard.
>
> None of this helps you with your quest for the schematic, but it would be
> a significant task to reverse-engineer the schematic from the hardware,
> and you would still have to reverse-engineer the firmware (programming) of
> the micro-controller.  Having done this, you would then have to figure out
> how to re-program the controller for new cells.  In the end, the solution
> might be fairly simple, but getting there could be a long journey.
>
> There are replacement TP600 batteries available from non-IBM (Taiwanese ?)
> sources, so someone may have already gone to the trouble to do this.
> It seems doubtful (not to their economic advantage) that they would
> consider releasing the results of their work.
>
> I don't want to "rain on your parade", but rather just share what info
> I've gathered.  I hope you find some of this (way too-long) message
helpful.
>
> ++++++++++++++++++++++
> On  Wed, 03Dec03, James McKenzie wrote, in part:
> >From: James McKenzie <jjmckenzie51 at sprintpcs.com>
> >To: David Gemmell - VK4GL <david.gemmell at optusnet.com.au>
> >
> >David:
> >I don't think the problem is with the PCB, but rather with the placement
> >of the battery in the Thinkpad.  When I disassembled a 'dead' battery
> >for the 600 series, I found that the two cells closest to the CPU
> >(and a great source of heat) were "fouled"  and would not take a charge.
> >The other cells in the battery were just fine and continue to take a
> >charge.  I could rebuild the battery with new cells and I would expect
> >the 'new' battery would last as long as the 'old' battery.
> >
> >However, I don't know of a source for the schematic for the PCB.
> >Maybe, someone on the list can locate one.   >James McKenzie
> >
> >
> >David Gemmell - VK4GL wrote:
> >>I had seen that site, some excellent info,
> >>but I was really after the schematic of the PCB
> >>in the batt case to see where the design was astray.
> >>
> >>----- Original Message -----
> >>From: "James McKenzie" <jjmckenzie51 at sprintpcs.com>
> >>
> >>>There was a lengthy discussion on rebuilding 600 series batteries.
> >>>Look at the following site as it has instructions on how to rebuild
> >>>Thinkpad 600 series batteries:
> >>>
> >>>http://www3.sympatico.ca/milnoc/TP600Battery/
> >>>
> >>>It provides a great wealth of information on the 600-series
> >>>battery  problems and links on how to rebuild them. >James McKenzie
> >>>
> >>>
> >>>David Gemmell - VK4GL wrote:
> >>>>After reading many of the postings on TP600 battery pack
> >>>>problems, I would like to have a go at repairing mine.
> >>>>
> >>>>And - please - I do understand all the warnings about this -
> >>>> (the sky will fall in  - etc etc,)
> >>>>but I do have the required knowledge and equipment.
> >>>>
> >>>>Does anyone have a SCHEMATIC of the charge control
> >>>>circuitry which is built into the battery pack?
> >>>>Thanks David
> >>>>________________________
>
>
>
>