12 volts directly to 600E battery terminals?

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The IBM 600E battery is at 12.6 volts fully charged and discharges to
11 volts (according to the repair manual).  This looks a lot like the
charged vs discharged potentials of a deep cycle marine battery  My
plan is to remove the computers internal battery and feed 12 volts to
the + and - internal terminals (where the battery plugs in).  I believe
the need for the other two terminals is to individually charge the
LiIon cells.

Am I overlooking something obvious that will cook the computer???


Re: 12 volts directly to 600E battery terminals?

vburnham@gmail.com wrote:
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YOur computer may or may not let you put volts in the terminals
without connecting the others to the proper place.  Try it.

Remember that your battery can approach 15V fully charged.  That may
or may not be a problem.

The problem comes when you try to hook up a battery charger when
the laptop is connected.  That depends on your charger.

And if you REALLY want to blow things up, hook it directly to your
car battery and start the engine.

The negative battery terminal is probably not connected directly to
ground, even though your multimeter will try to convice you that it is.
IF you connect a modem, you can get a ground path thru there that can
mess up the battery sense system.

How are you gonna connect it all up.  Remember that anything that
CAN be hooked up backwards, eventually WILL get hooked up backwards.
Goodbye laptop.

So, the problem is not so much what you have thought about doing.
The problem is with the "little" incremental things that you are likely
to do later.

Why can't you stuff the volts in the external DC power connector?
Might not work, but worth a try.  Still doesn't solve your overvoltage
transient problems.

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Re: 12 volts directly to 600E battery terminals?

On 15 Sep 2005 15:46:22 -0700, vburnham@gmail.com wrote:

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The 600X (uses the same pack) will run down to 10.5V off the PS
jack so I would be inclined to try that since the PS is also 16V,
well within the marine's range  if there is no external charger on
the marine or  spikes well filtered out..

As you surmise, the other two terminals are for pack detection:
one is a thermistor, the other a data line.  Both must give
correct readings or charging will not occur although power can be
drawn from the pack (no fuel gauge in that case too and LEDs blink
annoyingly),  I'd be leery of connecting anything other than a
pack because there are probably no overvoltage or overcurrent
protection circuits on those terminals since only a small fused
and protected pack is expected there.

One thing I'd worry about is someone  plugging into the jack while
the marine is directly connected, again, due to design was for a
standard IBM pack and its current range.


Re: 12 volts directly to 600E battery terminals?


First, lithium batteries have a microprocessor in the battery that
communicates with the laptop.  Without this communication, the laptop
may not work.

Second, the lead-acid hi-capacity battery may damage the charging
circuits of the laptop by looking too much like a short-circuit.

Finally, even ignoring both of the above issues, connection to a battery
may be ok, but do not attempt to connect the laptop directly to the
power bus of a vehicle (car, boat or airplane) even if it's nominally
the same voltage.  Vehicle power systems have incredible spikes on them
that can destroy a laptop.

vburnham@gmail.com wrote:
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Re: 12 volts directly to 600E battery terminals?

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12.6 volts corresponds to a fully charged Li-Ion battery that has 3 series
cells (or (more usually in Laptops) several paralleled 3 cell blocks).
However the fully discharged voltage of such a battery is 9 volts.  There is
quite a bit more to the interface with the battery.  Most contain battery
monitoring and charging circuitry which communicates with the Laptop via
those extra terminals that failed to escape your notice.  With nothing
connected, the Laptop may assume that the (missing) battery is either
faulty, discharged or both.  It may even attempt to charge your external

Personally, I wouldn't recommend your intended course of action.

If you really want to run the laptop from a 12 volt external submarine
battery (it's marine isn't it?), you would be better off obtaining a
universal type laptop power supply which includes the ability to operate
from car and aeroplane electrical systems.  The added bonus is that it would
also charge the official battery if required.

Re: 12 volts directly to 600E battery terminals?

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The downside is efficiency. If you come in through the DC input, you're
almost certainly going through one more regulation stage than if you
come in the battery terminals.

Re: 12 volts directly to 600E battery terminals?

zwsdotcom@gmail.com wrote:
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Does it really matter? Laptops have been designed, like it or not, in
such a way that trying to bypass the corresponding constraints will
almost certainly harm them. So, yes, theoratically you may be right, but

John Doue

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