My battery is stuck at 18% and wont charge any farther than that but the battery will decrease. why?

During the initial state of the charge, the charger operates in a fixed-current mode. This means that the current will be held at a constant rate until the battery is charged to a bit over 18 Volts. During this phase, the output of the charger will not be 18 Volts. This is done for safety and battery preservation; forcing 18 Volts on a battery discharged down to 15 Volts or less could cause the battery to overheat. If no battery is connected, the charge controller may hold the output low until a battery insertion is detected.

The exact behavior of the charger depends on the chemistry for which it is designed, whether Nickel-Cadmium, Nickel-Metal Hydride, or Lithium ion. If the output of a known-good battery is 18 Volts after charging, and it has normal capacity, the charger is working properly.

However, a bad cell in the battery changes things. If you run a Ni-Cd battery down too far, the weakest cell in the battery may begin to reverse charge from the current coming from the other cells. This usually causes an internal short circuit, and the cell will be stuck at 0 Volts. A battery pack with one shorted cell will read 16.7 -16.9 Volts when fully charged, and the drill will not have the peak power it should. The charger will give you a battery fault indication if it is equipped to do so.

Batteries do not last forever, you may simply need to replace it

You can't "restore" it.

Replace it!

memory card slot/battery cover was opened with power on.
2) test the battery for full charge, and the same type alkaline
and the same direction.
3) Full charge batteries.
4) clean contacts batteries with c. cleaner
God bless you

Typical behavior of a faulty battery, cells are not accepting full charge... If its still under warranty, you can get the battery replaced no charge, otherwise you're in to fork out over 100 USD for a new battery pack.

:)

The battery could be faulty or the charging circuit is faulty. I suggest you return it to the supplier for repair or replacement as this netbook would still be under warranty.
If you try to repair it yourself you may void your warranty.

If your battery is a lithium ion battery then according to the folks at Battery University:
"The worst condition is keeping a fully charged battery at elevated temperatures, which is the case with running laptop batteries. If used on main power, the battery inside a laptop will only last for 12-18 months. I must hasten to explain that the pack does not die suddenly but begins with reduced run-times"
see their website at : http://www.batteryuniversity.com/parttwo-34.htm
Hope that helps.
Lori

Each time you charge your battery, the charge capacity is decreased. After a large amount of charges, the capacity is decreased to an amount only enough to turn on a/the screen(s) for a second. Try getting a new battery.

no its best just to replace them

check fuses on AMP , fuse from battery under hood , .It should not be farther than 18 inches from battery meaning the fuse..