I have a dell laptop. I'm not sure if my battery is dead. It says that my battery has 90% power. The only way for me to keep my laptop on is to keep the power cord plugged into the batter at the back of the laptop. Am I missing a setting that needs turning on or is the batter dead?

Most likely it is dead.

If you have a volt-meter you could check your battery.

I think BADBOY is right... but it should be noted that the voltage could be fine and the battery still shot.

The voltage charge on a shot battery is usually still there... it's the current output that usually falls off on an older battery.

A simple way to test this is to test the amp-hour (AH) of the battery. On the sticker it will say (for example) 2AH. This means that the battey should power a 2 amp device (a car stop light bulb) for a period of one hour...

I had one that said 100 percent and 3 minutes later it was dead

I had one that said 100 percent and 3 minutes later it was dead

That would be the current drop off... A laptop battery is a pile of smaller banks of batteries hooked in parallel. The more you parallel, the more your current output will be. On the same hand, the LESS you parallel the less the current output... voltage will be the same. So if one bank goes bad (which is what happens) the voltage will still be the same... but the current output drops.

Here's the hooker: Laptop power meters measure VOLTAGE, not CURRENT.

My Dell battery has a button to push and a series of 5 green dots (like an LED) that light to show battery health. Less than 2 and you need to replace. See if your battery has that feature.

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