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Old March 3rd 17, 07:33 AM posted to alt.comp.os.windows-10,alt.comp.os.windows-8,alt.windows7.general
Paul[_32_]
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Posts: 11,873
Default How to interpret laptop battery results.

Ken Springer wrote:

A couple months ago I did some research on how to maximize the life of
your battery.
I created a single page doc on taking care of your laptop battery. Main
points are as follows:

Simple ways to make your battery last longer...
1. Do not charge your battery to 100%. Heat is the enemy of battery
life, and charging to full charge creates internal heat in the battery,
which shortens the life of the battery.


http://batteryuniversity.com/learn/a..._ion_batteries

"Some Li-ion packs may experience a temperature rise of about 5ºC (9ºF)
when reaching full charge. This could be due to the protection circuit
and/or elevated internal resistance. Discontinue using the battery or
charger if the temperature rises more than 10ºC (18ºF) under moderate
charging speeds."

"Li-ion cannot absorb overcharge. When fully charged, the charge current
must be cut off. A continuous trickle charge would cause plating of
metallic lithium and compromise safety. To minimize stress, keep the
lithium-ion battery at the peak cut-off as short as possible.

Once the charge is terminated, the battery voltage begins to drop.
This eases the voltage stress. Over time, the open circuit voltage
will settle to between 3.70V and 3.90V/cell. Note that a Li-ion battery
that has received a fully saturated charge will keep the voltage
elevated for a longer than one that has not received a saturation charge."

The necessary behaviors are handled by the internal chip in the laptop
in charge of doing the charging. A well-matched battery chemistry, along
with the right settings on the charger chip, ensures carefree operation.

On the other hand, the article here talks of "thermal runaway".

http://www.batteryuniversity.com/lea...of_lithium_ion

The article here, has a graphic. It's when the charger goes "out of bounds"
that the trouble begins. The charger (a chip inside the laptop), has to be
matched to the battery chemistry. Buying a cheap replacement battery, which
happened to have the wrong chemistry, could promote this kind of failure.
You're relying on the guy in China, putting the right cells in
your cheap replacement. And with Cobalt, there can be some slight
differences. For the guy building the packs, he should have
datasheets for both products in front of him, to verify they're
correct.

http://www.mpoweruk.com/lithium_failures.htm

So under normal circumstances, the battery experiences negligible
self-heating at full charge, and the charging stops after the topping
up phase. You may feel a warm spot in the laptop, but that should
be in the power management area, not the battery.

2. Do not fully discharge your battery by letting it die.


The laptop will shutdown at 0% charge, so the battery is not
immediately un-chargeable. However, if you leave a pack that is
at zero percent in that state for too long, the self-discharge
of the pack (not the load from the laptop), will take it below
the safe charging voltage level. And then the charging chip
will simply refuse to charge it, for safety reasons. The pack
must then be replaced. (And if you're an idiot, you drill into
the pack and apply a charge to the cells, you could start a fire.)

In summary, running the battery to 0% is perfectly safe... as
long as you recharge it in a reasonable time after it happened.
And this is not always under your control. The computer can
do this on its own, while you would assume there is "fuel left
in it".

This happened to me just recently - the puzzle was, how did the
laptop discharge the battery ? It was maybe 50-60% full when shut
down, and it read 0% when I tried to use it two weeks later.
(I always check for the flashing sleep LED - it wasn't sleeping.)
The OS was Windows 10... I suspect the computer came on,
with the lid closed. Task scheduler. My new policy from
now on (like right now as I type), is to pull the pack
from that thing. It's self discharge properties are
still pretty good.

3. Try to keep your battery charged to between 40%-70%.


Sounds good. Promotes longer battery life in years.

4. Try to keep your battery at room temperature. So don’t leave your
computer in a hot or cold car, for example.


In particular, a well-designed charger chip, will refuse to
charge Li at low temperature. If your laptop comes in from
a -20C car, let it warm up to room temp before plugging it
in for charging. There is a limited temperature range for
proper charging, and it's up to that charger chip to enforce
the rules.

5. If your AC adapter (charger) fails, ensure the replacement charger
matches or exceeds the specifications of the original charger. Also see
if you can determine if the charger you are buying includes some safety
circuits, such as a temperature sensor that shuts the charger down in
case the charger gets too hot. That will prevent the charger itself from
failing.


At the very least, it should match on DC voltage. Replace an 18.5V
adapter with an 18.5V adapter. Typical rules are +/- 0.5V. Use a multimeter
if you suspect the "universal" replacement you got isn't right for the job.
If a universal adapter only has a "low/high" switch, you'd better check
the output voltage.

Paul
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