laptop only runs on a/c power

I have a Toshiba tecra A8 and I can't figure out this problem.  The laptop only stays on when plugged into the a/c charger.  However, Windows XP tells me that the battery is 100% charged, but if I unplug the a/c adapter, the laptop immediately turns off.

I tested the a/c adapter with a multimeter and it's working.
I tested the pins coming off the motherboard that go to the battery and they're getting power.
The battery charge light on the front of the laptop is telling me the battery is charging.
And Windows is telling me that the battery is charging (when plugged into a/c) and that it's at 100% charge.

any ideas?
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Steven HarrisPresidentCommented:
Sounds like you have some dead cells.
Emmanuel AdebayoGlobal Windows Infrastructure Engineer - ConsultantCommented:
The battery is not charging even though the laptop is saying charging.

You will need to replace the battery.

MalamamotoAuthor Commented:
ok, sounds like it's the battery.  New battery here I come.
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MalamamotoAuthor Commented:
for future reference, is there a way to test a battery with a multimeter?
Emmanuel AdebayoGlobal Windows Infrastructure Engineer - ConsultantCommented:
Checking Battery Charge with a Multimeter

Step 1

Fully charge your laptop battery.

Step 2

Turn off your computer and remove the battery. Look for a voltage rating printed on the battery. This will be the number to compare with your multimeter reading. Many laptops have voltages of 9.6V, 10.8V, 11.1V, 14.4V or 14.8V. Some have lower or higher ratings.

Step 3

Look for the connector where the battery interfaces with the computer. It will be near the center of the side of the battery that faces the computer when plugged in. Roughly an inch in length, it should resemble a series of at least five very narrow, identical slots that looks a little bit like your laptop’s exhaust fan grating, except smaller. The outermost of these slots will be the positive and negative terminals of the battery.

Step 4

Turn on your multimeter and set it to measure direct current voltage on the 20-volt scale (or anything close to 20 volts). Voltage settings are indicated by the letter “V” and direct current voltage settings are indicated by straight lines near the V, as opposed to wavy lines for alternating current.

Step 5

Insert one prong of your multimeter into the outermost slot on one end of the battery connector. Insert the other prong of your multimeter into the other outermost slot on the connector. It doesn’t matter if you match your positives and negatives. If you get them backward, it will just change the sign of the voltage, not the actual number, and the number is what’s important. Make sure each prong is touching bare, exposed metal.

Step 6

Observe the reading on your multimeter. A fully charged, healthy laptop battery will measure very close to the printed value on the battery.

Step 7

Try measuring your battery’s voltage after a 60- to 80-percent discharge, to get a comparison against the full charge value. A depleted laptop battery won’t measure anything close to 0V. There will still be several volts in it. What happens is that, once the battery drops below a certain voltage, your computer automatically shuts down. This is because if the voltage drops too low the battery will become damaged. Protective circuitry in the battery will then make it impossible for you to use a dead battery.

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MalamamotoAuthor Commented:
What great information!  I did that and my battery is rated for 10.8 volts and I was only getting 8.0 volts.  and it's telling me it's 100% charged.  What does this mean in terms of what the problem is with the battery?  I know it's a bad battery, but what causes this to happen and what can I recommend people to do to prevent this?  Thanks!
Emmanuel AdebayoGlobal Windows Infrastructure Engineer - ConsultantCommented:
I don't know how many cells are inside this battery, but it obvious one of the cell is dead. (it might be 5 cell of 2Veach)
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