Anyone familiar with NEC Versa SX at component level

  • Thread starter Lewin A.R.W. Edwards
  • Start date
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Lewin A.R.W. Edwards

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I'm currently using a Versa SX as my primary computer, and it _seems_
to have a battery charge problem, though the batteries themselves are
not above suspicion. I have six main batteries for this computer and
one secondary battery (for the CD-ROM bay). I'd like to hear from
anyone who has experience poking about in these machines at a
component level. I have several other machines of the same model,
which I can use for donor parts - but they all have nominally bad
mainboards (I think they were powered off during BIOS update) so I
can't do the obvious, which is switch out the mainboard.

Anyway, here are the symptoms:

#1 If I charge with the computer switched on, the charge process will
stop short of 100% - the charge LED is still on, but the battery
capacity remains stuck. The level at which it sticks seems to be
fairly constant for each battery; for example, one usually sticks at
39%, a different one at 14%, etc. If I unplug AC for a few seconds
then reapply it, the charge process resumes, but the battery only goes
up one or two % then almost immediately jumps to 100%.

#2 If I COMPLETELY discharge the battery by leaving the computer at
the CMOS setup screen, then apply AC with the computer switched off,
the charge process appears to complete normally (charge LED goes off
after about an hour) and battery reports 100%, but it only lasts about
ten minutes.

Note: I haven't yet tested the secondary battery. All I did so far is
charge it once; it went from 0 to 100% at a normal sort of rate but I
didn't test capacity.

The batteries are not above suspicion, but this really feels like a
problem with dT/dt sensing, maybe a problem with the ADC that monitors
the battery thermistor; symptom #1 really looks like the charge
controller is sensing, maybe erroneously, an overtemperature condition
that pauses fast charge mode.
 
Surely all you have got is a bad cell on the battery which isnt picked up by
the hardware which identifies the battery as working properly

The battery sends a signal to the hardware that the battery (ie 2 out of 6
cells or 14%) is charged properly as soon as it stops charging which it does
as soon as the last working cell is charged and the charging process moves
onto the bad cell and cant charge it any more?


"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0405070330.7215a4fb@posting.google.com...
I'm currently using a Versa SX as my primary computer, and it _seems_
to have a battery charge problem, though the batteries themselves are
not above suspicion. I have six main batteries for this computer and
one secondary battery (for the CD-ROM bay). I'd like to hear from
anyone who has experience poking about in these machines at a
component level. I have several other machines of the same model,
which I can use for donor parts - but they all have nominally bad
mainboards (I think they were powered off during BIOS update) so I
can't do the obvious, which is switch out the mainboard.

Anyway, here are the symptoms:

#1 If I charge with the computer switched on, the charge process will
stop short of 100% - the charge LED is still on, but the battery
capacity remains stuck. The level at which it sticks seems to be
fairly constant for each battery; for example, one usually sticks at
39%, a different one at 14%, etc. If I unplug AC for a few seconds
then reapply it, the charge process resumes, but the battery only goes
up one or two % then almost immediately jumps to 100%.

#2 If I COMPLETELY discharge the battery by leaving the computer at
the CMOS setup screen, then apply AC with the computer switched off,
the charge process appears to complete normally (charge LED goes off
after about an hour) and battery reports 100%, but it only lasts about
ten minutes.

Note: I haven't yet tested the secondary battery. All I did so far is
charge it once; it went from 0 to 100% at a normal sort of rate but I
didn't test capacity.

The batteries are not above suspicion, but this really feels like a
problem with dT/dt sensing, maybe a problem with the ADC that monitors
the battery thermistor; symptom #1 really looks like the charge
controller is sensing, maybe erroneously, an overtemperature condition
that pauses fast charge mode.
Click to expand...
 
Surely all you have got is a bad cell on the battery which isnt picked up by
the hardware which identifies the battery as working properly
Click to expand...
Yeah, but that doesn't explain to me why it goes to 100% once I reset
the charge controller (by cycling AC power) though. Also this laptop
was sold to me as "won't charge battery". I am not 100% convinced that
there is a problem with the laptop, but on the other hand I'm not 100%
convinced the batteries are all bad too. Kind of long odds, all six,
don't you think?
 
"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0405081102.11c7d36f@posting.google.com...
Surely all you have got is a bad cell on the battery which isnt picked
up by
the hardware which identifies the battery as working properly

Yeah, but that doesn't explain to me why it goes to 100% once I reset
the charge controller (by cycling AC power) though. Also this laptop
was sold to me as "won't charge battery". I am not 100% convinced that
there is a problem with the laptop, but on the other hand I'm not 100%
convinced the batteries are all bad too. Kind of long odds, all six,
don't you think?
Click to expand...
What I'd try to do is find a known good laptop or battery of the same type
and try it with the offending unit.
 
Hi James,

Yeah, but that doesn't explain to me why it goes to 100% once I reset
the charge controller (by cycling AC power) though. Also this laptop

What I'd try to do is find a known good laptop or battery of the same type
and try it with the offending unit.
Click to expand...
Why do you think I bought all those other units, I was hoping to get
something "known good-ish" :) Kinda spent all I want to spend on this
project, especially since I was just laid off.

In the time since my last message, I tested the secondary battery.
This battery appears to work perfectly normally; it lasts about 100
minutes, it charges slowly from 0-99% and then after a while clicks
over to 100% (presumably 0-99 is measured by the gas gauge IC and 100%
means "fast charge completed"). So the secondary battery port is known
good.

I also did a special test under Windows, with one of the main
batteries, all power management disabled: I started the machine with
the battery at 100%, it went down to about 97% then jumped to 8% (with
a "low battery" status LED) in 15 minutes, then VERY SLOWLY went down
to 0% - that took another 45-55 minutes. So my theory about an ADC
problem (or op-amp between battery and ADC) still looks plausible,
though I'm starting to think you're probably right.

My next step is to take the motherboard out of the housing and plug a
main battery into the connector for the secondary battery (pinout is
the same, but the plastics won't allow you to get a main bty into the
CD-ROM bay). If it charges/discharges OK like that, then I KNOW that
something is screwy about the sense lines on the main battery port.
Otherwise you are right and I just have a box full of bad main
batteries. I might break open the worst one and measure the cell
voltages just to confirm that. Not sure that it would be worth trying
to make one or two good packs out of the six bad ones, but I will
probably try.
 
Your discharge test is very indicative of bad battery. That is simply how
those batteries behave when they are bad.


"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0405081813.6a8ae10a@posting.google.com...
Hi James,

Yeah, but that doesn't explain to me why it goes to 100% once I reset
the charge controller (by cycling AC power) though. Also this laptop

What I'd try to do is find a known good laptop or battery of the same
type
and try it with the offending unit.

Why do you think I bought all those other units, I was hoping to get
something "known good-ish" :) Kinda spent all I want to spend on this
project, especially since I was just laid off.

In the time since my last message, I tested the secondary battery.
This battery appears to work perfectly normally; it lasts about 100
minutes, it charges slowly from 0-99% and then after a while clicks
over to 100% (presumably 0-99 is measured by the gas gauge IC and 100%
means "fast charge completed"). So the secondary battery port is known
good.

I also did a special test under Windows, with one of the main
batteries, all power management disabled: I started the machine with
the battery at 100%, it went down to about 97% then jumped to 8% (with
a "low battery" status LED) in 15 minutes, then VERY SLOWLY went down
to 0% - that took another 45-55 minutes. So my theory about an ADC
problem (or op-amp between battery and ADC) still looks plausible,
though I'm starting to think you're probably right.

My next step is to take the motherboard out of the housing and plug a
main battery into the connector for the secondary battery (pinout is
the same, but the plastics won't allow you to get a main bty into the
CD-ROM bay). If it charges/discharges OK like that, then I KNOW that
something is screwy about the sense lines on the main battery port.
Otherwise you are right and I just have a box full of bad main
batteries. I might break open the worst one and measure the cell
voltages just to confirm that. Not sure that it would be worth trying
to make one or two good packs out of the six bad ones, but I will
probably try.
Click to expand...
 
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