[ltp] battery dead?

[Jim Harvey]

It most likely won't work, especially if it's a Lithium battery.  Maybe if it's 
a nicad.  I've experimented with two 770 packs, it appears that the controller 
circuit board (which is surprisingly complicated) won't let current into the 
battery in the reverse direction. There must be some control taking place 
through the other pack terminals. I've taken the packs apart and tried to charge 
directly to the battery terminals with little success.  Lithium cells appear to 
go open in their dying stage. Lead cells go open at the end also.  Nicad cells 
short when they go to be with Jesus.

<warning> Trying the following may damage your battery or yourself.  A short 
circuited (good) battery can put out enough current to cause a fire or even 
explode </warning>

When experimenting, I use a CB type DC power supply with a tail light bulb in 
series to limit current.  I do have a couple of meters so I can check things. 
The smaller the light bulb, the less current gets through.  Crude but effective.

Here is a schematic of a kludge current regulator here.  I needs only 2 parts. 
You will need a fixed width font (courier) to see the drawing:

+12 volts --------\           _/-----/\/\/\/\------- + current regulated
                    \          /|     resistor   |      output
                     \        /                  |
                   --------------                |
                         |                       |
     Fat NPN Transistor  |_______________________|


-12 volts ------------------------------------------ - current regulated

Size the resistor to drop 0.7 volts at the regulation point.  By Alexander 
Graham Ohm's Law   R = 0.7/I  (where I is in amps).  For example, 350 milliamps 
use 2 ohms.  If you want better current control you can use an LM317 regulator 
in place of the transistor. LM317 application notes usually show this circuit. 
The problem is for higher currents, the value of R gets very small and it's hard 
to find small precision resistors.

Test the regulator with a current meter connected to the output terminals before 
you hook it to your battery.

The current does not have to be precise to charge a battery.  A rate of 1/10 of 
the battery capacity in amp-hours is considered harmless to the cells if you 
leave it on too long, and that's where that figure came from.  Less current is 
OK, it just takes longer to bring the pack to a full charge.  Hopefully, you 
just need to get the pack up to a voltage level where the charge controller in 
the computer doesn't think it's shorted out and will take over.


Kelvin KAN wrote:

> I have the same battery problem with my 600E.  I believe it was not due
> to Linux.  The battery capacity was getting shorter and shorter, then
> finally flashing amber w/o being charged for a day.
> 
> I remember someone also in this mail list suggested it was due to the
> voltage dropped below the minimum required by the microcontroller within
> the battery.  The fix was to apply 6V and 1/10 current of the mAh spec
> of the battery to the +/- terminus, to wake it up.
> 
> I've never done that due to the fact that a constant-current power
> supply would be comparable with the price for a new battery.
> 
> Has anyone got a cheaper source of constant-current power supply?  Like
> the circuit of building a fixed-volt&amp one (because we know we need
> exactly 6V/0.18A) using very cheap passive components (assuming the
> unregulated power is from the existing TP600 16V power supply). 
> 
> Thanks,
> -
> Kelvin.
> 
> Xun Cheng wrote:
> 
>>After a resume from a successful hibernation under
>>linux, my battery keeps reporting 0% charge. I'v put
>>on AC power for half a day and the battery light
>>keeps flashing every several minutes. It seems
>>no charging has been done.
>>
>>Any suggestion other than buying a new battery?
>>
>>Some facts:
>>. It's a Thinkpad 600X.
>>. It's redhat limbo beta.
>>. I seldom use it without AC power.
>>. I removed AC power before hibernation (otherwise
>>  it won't hibernate).
>>. The linux is installed on the ultrybay second HD.
>>. The hibernation partition is on the internal
>>  first disk which was mostly spined down until
>>  hibernation time.
>>
>>thanks a lot
>>xun
>>
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>>
> 
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> 


-- 
  After Armageddon, there will be only three things left,  Kudzu vines creeping
  over the ruins, Cockroaches feasting on the blackend ashes, and somewhere
  an IBM PC saying "Abort, Retry, Ignore -- Abort, Retry, Ignore"
  Jim Harvey - WB8NBS/9 - Naperville, Illinois - Linux on a Thinkpad 770Z


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