I recently picked up a "new" Portege 3000 series battery (PA2467UR -
2600mAh) which appears to be in mint and unused condition. Unfortunately it
will only deliver just over an hour of online time (from 100% to about 15% -
I won't go lower for obvious reasons) with medium CPU speed (quiet cooling,
lowest brightness setting, Speedstep set to "Battery Optimised"). This
compares poorly with an old hefty high-capacity battery (PA3039U-1BRL -
5600mAh) which delivers well over 4 hours (5 with low power management
settings). At just under half the capacity I would have expected this
PA2467UR battery to deliver around 2 hours on-line time?

The battery doesn't show a sudden drop in charge percentage which is typical
of a pack coming to its natural end.

So, I'm wondering if anyone has experience of using this battery in a
Portege 3440/80/90 and can report back the average power-on time for a good
condition battery with similar PM settings? Its being used in a 3480CT
(PIII-600MHz Speedstep).

Fortunately the seller has a very fair no-quibble refund policy - just need
to know others experiences so I can either avoid these or look elsewhere as
they may have a batch that is old or has been stored incorrectly.

Thanks,

AlexQ

~ Reply To valid ~

I would cycle the battery 2 or 3 times to see if it improves. Charge it
to 100%, discharge to 25% or so (not lower), you've already done one cycle.

However .....

When you cut the capacity (mah) of a battery in half, you cut the life
of the battery MORE than in half, sometimes a LOT more. Batteries
provide the most total power when the discharge rate is relatively low,
while you have gone in just the opposite direction, keeping the
discharge rate constant bud dropping the battery capacity in half.


Alex Quant wrote:

"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:41323D24.6080404@neo.rr.com...
Thanks for your response Barry. The pack has been through 3 cycles so far
without a noticable improvement. Not sure about your assertion that half
capacity often means WELL over half on-line time with similar usage
patterns - that sounds counter-intuitive, but this may well be how things
are with laptop battery packs! ;-)

I'm open to the idea this is typical of a good condition battery - just
disappointed it appears to give poor performance. I daren't imagine how the
1300mAh version performs! :-o

AlexQ

~ Reply To valid ~

The point that I was trying to make is that you can withdraw a lot more
total amp-hours from a battery over 20 hours than you can over 1 hour.
That is, if you determine the number of amp-hours that deplete the
battery completely in one hour, and the number that depletes it in 20
hours, the 2nd number is a lot larger.

By the way, 20 hours is the "standard", I believe, for determining the
rated capacity of a battery.

But the draw from a laptop is far greater than that, so if a given
laptop draws 1 amp and the battery is reated at 5000 mah (5 amp-hours),
you cannot expect the laptop to run off of that battery for 5 hours, it
will be less than that, quite a bit less. BUT, that same battery would,
in theory, power a light bulb drawing 250 ma (.25 amps) for 20 hours.



Alex Quant wrote:

Barry Watzman wrote:
Most of the failures I've seen in LiION batteries have been high
internal resistance. The resistance causes voltage drop at the high
peak currents of the laptop. The low voltage cutout senses this low voltage
and shuts off the computer. You still have a LOT of capacity in the
battery, but the computer won't let you have it.

Note that the average current drain is very much affected by power
saving modes. The peak current, not so much...
The peak current times the internal resistance is what causes the
computer to shut down.

What laptops should do is measure the battery's internal resistance
and compensate for it in the low-voltage cutout algorithm.
mike

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Bunch of stuff For Sale and Wanted at the link below.
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"Alex Quant" <alexqspam@yahoo.co.uk> wrote in message
news:2pes4eFk8oh7U1@uni-berlin.de...
Well, I now have a second user PA2467UR 2600mAh Portege battery and .. it
delivers around 2 hours from full to 20% charge (low screen brightness,
quiet cooling and medium CPU speed) as I would have reasonably expected!

AlexQ

~ Reply To valid ~