Re: Laptop won't turn on, charging LED doesn't glow

In alt.comp.hardware, on Fri, 27 Aug 2021 02:01:05 -0400, Paul
<[email protected]> wrote:

>micky wrote:
>> My laptop is plugged in but it won't turn on and the LED that shows it's
>> charging isn't lit, even though it's plugged into a charger and the
>> charger output is measured just now at about 17vDC
>> 
>> I'm not surprised the battery is dead, I haven't used it for 6 months or
>> more, but I do remember the charging-led working the last time it
>> worked. 
>> 
>> This seems like an unusual sort of failure.   Does it seem very
>> improbable to you too? 
>> 
>> After "charging" for 30 minutes, it still won't turn on and the CD drive
>> won't open by presssing the button.   Is there a reset I don't know
>> about?  Could a failed battery keep the light from going on?  Shouldn't
>> it run off the charger even if the battery is bad?  I know the answers
>> are No, No, and Yes, but I'm grasping at straws. 
>> 
>> 
>> A friend gave me this Acer aspire E15, also called an E5-573-35AQ
>> 
>> It worked fine when I got it and I added software. I think I bought a
>> new psu to replace the missing one.  
>> 
>> Does this sound like something a very handy person could himself? 
>> 
>> (My friend called me to ask if he had left certain software on it.  I
>> don't think so but I was checking.  If it's broken it's a good thing I
>> know now instead of just before I leave on a trip.)
>
>The pack has probably run down, below the charging threshold.
>
>The internal charge management, won't shove any charge into it at
>all, if it does not meet the minimum voltage. When it goes below
>the minimum voltage, one or more of the cells will reverse bias
>and metallic lithium plates out, which is a fire hazard.
>
>Discharge       Full +--
>Curve                |  \  <--- Store pack, slightly less than full
>                      |   \
>                Empty +    +-- Hibernate -
>                      |                   \__
>              TooLate }                      \______ CanNotCharge
>
I think I caught it just before cannot charge. 

>If you run a laptop so low, that the battery display reads "0%",
>the pack voltage is still above the minimum by a bit. If you
>drain a laptop, hibernate it, then put it in a closet for three
>months, this would be bad, as it could drop to CanNotCharge.
>That's why, if putting a laptop away for months on end, you
>pull the pack (pack will still "self-discharge"), and ensure the
>battery display read about 80% before disassembly. That's how mine
>is stored right now - pack out (which runs down the CMOS CR2032 of
>course, so that's the tradeoff - CMOS cells are cheaper than packs.)
>
>The battery management chip inside the pack, could have written
>in it by the computer, that the pack has been to the CanNotCharge
>voltage and even if you "lifted" the cells individually, it would
>not help. If you lifted the pack, artificially above "Empty",
>there is no particular reason for the charger to try to refill it.
>It reads the battery management chip over the serial bus on the
>multi-contact pack connector, and discovers that status bit.
>
>By reading the serial bus connection to the battery pack, the
>log information about pack health can be read by the computer.
>Any similar model of machine could read it, and come to the
>same conclusion it should not be charged (for safety reasons).
>
>Now, in a past time, lifting the cells might have worked, because
>Battery Management did not babysit the user quite as much.
>
>Pulling the pack, the laptop should run off the wall adapter.

I should have tried that.  Panicked I guess.  Next time I will think of
it.  

I don't really need to run on the battery unless I want to take the
thing to another room  without turning it off first, and its good in
case of a power failure, although those are rare, 


>Mine does. Any time you plan on doing a lengthy calc with
>a laptop, unplugging the pack avoids attempts to keep
>charging the thing, over and over again. Storing the pack
>at 80% full makes more sense than keeping a laptop running
>constantly with pack in place, and the pack averages 95% to 100%
>charge (which is not good for the pack lifetime).

I wish there was a way to leave it plugged in but only going to 80%.
Phones are the same way. 

>Back in NiCd days, the batteries functioned as a "regulator",
>in really cheaply designed product. Pulling the cells from
>such units, could "blow" the laptop. But on modern Lithium Cobalt
>systems, the regulation and MOSFET features are such, the laptop
>is protected from most user-orchestrated catastrophes.
>
>Pull pack, plug adapter to laptop, and test it still works.
>
>No blue charging light is coming on again, until a new pack
>is presented to the machine, one above CanNotCharge voltage
>and no record in the battery chip, of abuse.
>
>Make sure that the voltage listed on the adapter, is what
>appears on the adapter contacts. On a 19V adapter, the output
>voltage should be +/- 0.5V, which means 18.5V is valid and
>19.5V is valid. Any value between those two, is close enough
>to make it work. "Universal adapters" on occasion, are way
>off from the desired value, which is why the magic smoke
>comes out a month later. While the third-party manufacturer
>claims it is "Universal", the laptop manufacturer made some
>assumptions too, about how close the custom adapter
>provided, has to be to a "correct voltage" value. If
>the laptop expects 19.0V in, the adapter is not allowed to be
>too sloppy.

IIRC I did buy a replacement, and not factory which was expensive, and
it might only be 17v, but it was hard to hold the probes to the plug. 


Thanks, and thanks Vanguard

>    Paul