Re: Issue with notebook (maybe the battery?)
On Sun, 26 Mar 2017 16:38:29 -0300
Daniel Bareiro <daniel-listas@gmx.net> wrote:
> Hi, Richard.
>
> On 26/03/17 06:46, Richard Owlett wrote:
>
> >> [snip]
> >>
> >> 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.
There's a time sequence: first, with a completely discharged battery,
which will have been disconnected by its own internal electronics, a
significant current charge is given and the cell voltage monitored
(calculated for a multi-cell battery). If it does not exceed 3.0V
within a few minutes, the charger gives up and produce an error signal,
the battery is faulty. If all is well, the recommended charge current
for the cells, normally about half the capacity i.e. about a two-hour
charge, is applied until the voltage reaches about 4.1V/cell, when the
charger switches to a third mode to bring the output voltage to
precisely 4.2V. During this mode, as the cell reaches full charge, the
current drops away and when a particular value is reached, the charger
cuts off. No further charge will be applied until usage or
self-discharge of the cell reduces the voltage to below about 4.1V. If
a charger is connected to a battery that is already charged to between
3.0V and 4.1V per cell, phase two is immediately started, and if the
cell voltage is already between 4.1V and 4.2V, nothing will happen.
There is no continuous trickle-charge mode. Assuming, of course, the
charger is designed properly, and with a specialised IC, this is pretty
much guaranteed.
So a lot of warnings about overcharging, memory effect, about removing
the battery when external power is used, and suchlike, are hangovers
from the days of nickel battery technologies, and don't apply to
lithium. Conversely, the charger has to be matched to the battery
capacity, and there's no way to charge lithium batteries with any kind
of general-purpose charger, you need the supplier's own charger, which
may be built-in to the appliance.
>
> >> 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.
>
> 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.
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.
--
Joe
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