Re: Issue with notebook (maybe the battery?)
On Mon, 27 Mar 2017 14:54:25 -0300
Daniel Bareiro <daniel-listas@gmx.net> wrote:
> Hi, Joe.
>
> >>>> Checking the purchase invoices, I bought the notebook on
> >>>> September 19, 2013, and then changed the battery on November 2,
> >>>> 2015. So less than two years ago I have this battery.
> >>>>
> >>>> The notebook I use it practically every day and I leave it
> >>>> sleeping from one day to the next so I do not have to open every
> >>>> application every time. I'm not sure if that impacts so much on
> >>>> the battery life.
>
> >>> If it was a long term degradation, possibly. With some battery
> >>> technology/technologies(?) there is a "memory" effect. If there
> >>> is a repeated "shallow discharge"/recharge cycle ( sleep overnight
> >>> followed by running during day with charger plugged in) the
> >>> effective battery capacity will decrease. IIRC that applies to
> >>> only one technology but can't remember which.
>
> >> I remember that when I bought this battery, I was advised to leave
> >> the charger plugged in for a little more than an hour after the
> >> charging level reaches 100%. And for the subsequent times, try to
> >> avoid having the charger plugged in when the battery charge level
> >> reaches 100%. So I was following that criteria. What do you think
> >> about that?
>
> > I would hesitate to contradict a supplier, but a lithium battery
> > charger should not permit overcharging. It *must* not, as there is a
> > serious risk of fire or explosion, not just a reduction of life as
> > will occur with other types. The maximum charge voltage must be a
> > fairly precise 4.20V per cell, and really the only practical way to
> > charge these batteries is to use one of many specialised integrated
> > circuits designed to do just that.
>
> I think he made that recommendation about disconnecting the charger
> when the charge reaches 100% because he thought otherwise would
> affect the battery life.
As I say, it shouldn't. Lithium chargers don't provide a continuous
trickle charge. Various sources on the Net claim that life will be
longer if you never fully-charge the battery, but with a laptop, you're
always going to be looking for maximum running time. Supposedly it's
best to store the battery for long periods half-charged, but then
whenever you need to use the laptop, you have about an hour to wait for
full charge. You can't win.
>
>
> Very interesting what you mention in these paragraphs. So in this
> case a measurement on the battery would have to give a voltage
> between 3.0V and 4.1V per cell if the battery works correctly?
Pretty much. The discharge protection should come in about 3V, but
might allow discharge a bit further. There is little energy left in the
cell at 3V. Here's a set of discharge curves at various currents:
http://www.richtek.com/battery-management/img/battery-discharge.png
>
> >>>> But in any case, in all this time, whenever the battery was
> >>>> charged, the charge level was up to 100%. So just since yesterday
> >>>> I suddenly saw that the load stayed at 38% and I started to
> >>>> experience this issue.
>
> >>> That makes me think of a component failure. Likely the battery,
> >>> but conceivably something in the laptop.
>
> > Yes. The problem is that it's not possible to rig up a quick
> > charging test for lithium, or a dummy battery load to check the
> > charger. With other technologies, a current source powered from a
> > higher voltage, with a voltmeter, would give some idea of the
> > battery state.
>
> Do you think the problem might be in the charger?
Yes, certainly. That's why I said it's difficult to know what's going
on without either a known good battery or a known good charger. You'd
better hope it's the battery, as that is easy to fix...
> At the beginning I
> had thought that maybe not since the notebook works when it is
> connected. Although perhaps it could be that if the electronics that
> manages the phases that you mentioned before is physically in the
> charger, the problem is in the charger.
The external power for the laptop is separate from the charger
electronics. The charger must supply a defined current, and if some of
this were diverted to run the laptop, it would be difficult for the
charger to monitor the state of the battery. So the external power is
supplied to two paths, to the laptop electronics and to the charger,
with laptop power being taken from the battery when the external power
is not present.
>
> >> Perhaps the ultimate test is going to a business where they have
> >> original Lenovo components, ask them for a new battery to test it
> >> at the moment with the notebook and, if all goes well, then buy
> >> it.
>
> > Sadly, that's the only real test.
>
> Earlier I telephoned the supplier where I bought this battery and he
> offered to test (without cost) my notebook with a new battery for a
> full charge cycle to make sure the problem was in the battery.
You are lucky. Many suppliers have neither the equipment nor the
willingness to help after the warranty period.
>
> > Something worth trying if you have access to a voltmeter: the
> > battery pack will have at least three terminals, maybe more, and a
> > voltage should be measurable across two of them. The voltage value
> > may show a missing (shorted) cell. Discharged as far as possible, a
> > lithium cell should be around 3.0V, and fully charged, 4.2V. The
> > battery should be marked as to how many cells it contains. If you
> > get a reading of less than 3.0V per cell, there is almost certainly
> > a dead cell. Probably you won't get a conclusive reading, if the
> > charger thinks there's 38% charge, then the volts per cell is
> > probably higher than 3.0, which it can be if one cell is missing
> > but the others are well-charged.
>
> I have a multimeter, so I could try that. This is a 6 cell battery.
> Here [1] are the specifications of Lenovo in case this is useful.
>
So you're looking for 18V or more. But five well-charged cells will
give you 20V...
--
Joe
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