Windows 7 - Battery only charges to 87 %

Asked By Anders F on 03-May-07 03:37 AM
I got a new battery for my laptop but it never fully charges.

I have done as the instruction says, charged and fully discharged
several times but the power indicator never says more then
87 % (well, the first time it said 87, then 90, then 87, 87) .

Discharging takes aroun 4 hours with the screen on and the
disk activity lamp flashing about every 5:th second so I
hope the battery is sound. After charging for 24 hours
the battery is not warm so I suppose the charger is not
putting a lot of current through the battery to charge those
last 13 %.

But I am not sure. Can anybody tell me if I can trust the
battery? If the battery is OK, is there any way to make
the system show 100 % instead of 87 when the
battery is fully charged?

The battery is Panasonic 4460 but I could not find
anything about the problem on their home site

Thanks for any answer

Og replied on 03-May-07 04:49 AM
Did you calibrate the new battery for use in _your_ laptop, as per the
instructions of the laptop manufacturer?
Anders F replied on 03-May-07 06:50 AM
Yes, I only have one laptop

JohnO replied on 03-May-07 08:25 AM
The only danger, and I chose that word carefully, is that the laptop keeps
charging a fully charged Li-Ion battery. That's A Very Bad Thing and could
quickly get exciting, something that you don't want.

From your good description IMO the problem is the charging circuit and the
function that measures the remaining charge. Apparently the circuit doesn't
know about your new battery, and the calibration function isn't making the
circuit any smarter. I have to assume that you didn't buy the battery from
the laptop manufacturer, and that's probably the root cause of the problem.
It should be solvable so check with the battery retailer, they have
certainly dealt with this before.

-John O
LVTravel replied on 03-May-07 10:59 PM
You say "yes" to the calibration of the battery.  Really?  You went into the
bios and ran the battery calibration routine that most laptops now have to
recharging is NOT a battery calibration.
Anders F replied on 04-May-07 12:05 PM
In the instruction that followed the battery, they said that running
down and recharging the battery is calibration. I had not thought
of checking the bios but when looking it did not have any
calibration routine (it is some years old). The bios does have a
battery page but it only shows the battery charge.
Of some reason the bios shows 95 % while I get 91 % when I
use the Power Options (well, it is better then the 87 % I got
last time).

JohnO replied on 04-May-07 02:57 PM
Sometimes it is...but many machines have special tools for this that are far
more accurate. Some older HP machines had a control panel tool for new
machines/batteries, so if it isn't in BIOS check with the manufacturer of
your machine.

-John O
NoConsequence replied on 04-May-07 02:13 PM
On Thu, 3 May 2007 09:37:21 +0200, "Anders F" <>

Is this indicated in Windows or the actual capacity meter on the
battery?  If the latter,the problem lies with the battery and the
subject is out of place here.  If the former, you need to calibrate
the battery with the OS.
JohnO replied on 05-May-07 10:08 AM
Get a life, you moron.
Anders F replied on 05-May-07 11:13 AM
The readings do vary, last full reading was 95 % in the bios and
91 % in the Power Options.
What capacity meter on the battery? I have not seen any such thing.
How do I calibrate a battery with the Windows?
FeMaster replied on 05-May-07 05:41 PM
Don't pay any mind to No Conscience, I mean, No Comprehension, or

You need to go to the website of whom ever made your laptop.  There will be
software there to accomplish the task of calibrating the battery to the

Example, older Compaq machines that were popular (m700, etc.) use "Compaq
Power Management" software to assist in power management and battery
calibration.  This can be found here:
JohnO replied on 05-May-07 08:23 PM
Most laptop batteries today have a meter built in, but it is usually four
lights representing 25%, 50%, 75%, and 100%. I doubt too many (any) of them
have real digital readouts.

-John O
Paul replied on 06-May-07 03:15 AM
If they put a chip in there, it can be pretty sophisticated.

industry's first high-performance fuel gauge IC"

Anders F replied on 06-May-07 03:55 AM
It's an old Dell Inspiron 4000. I checked Dell's site and all I could find

at 100% charge. If it is not, charge the battery until it reaches 100% in
the BIOS."

Not much help.

I tried the Compaq utility (they are both Windows so I hoped it would work).
Although I was logged on as administrator, it said it could not be run
I was not logged on as administrator.

JohnO replied on 06-May-07 05:00 PM
Your right Paul, but we're talking two different things here. The chip
that's in virtually every Li-Ion battery pack ever built indeed has fine
resolution. It must, because overcharging Li-Ion is a big deal, where with
NiCd and Ni-MH they can handle small overcharges without trouble. In PCs,
this chip talks to the BIOS and OS. It can keep track of things like the
number of recharges, and the expected life left in the pack.

Today's laptop battery packs have a button you can press. The resultant
display is as I noted.

-John O
FeMaster replied on 07-May-07 01:02 AM
It is possible that the software you seek is contained in one of these

I see there is also a BIOS update listed.  You could try that as well to see
if the function of calibration was added...