Macbook won't charge

SOURCE: Black macbook 13 will not boot.

you have logic board problem, check out if the fan, processor , harddisk working if not then it is logic board.
go to apple care and get the assistent.
plz rate this article. if you satisfy..

SOURCE: macbook wont turn on

Dont buy a new one as we may be able to repair. These boards are Not Complex by Industry standards and weve had excellent luck tracking and repairing them. (So Glad Apple went Intel).. Talk soon...

SOURCE: macbook Battery Problems

Hi Molle
To answer your last question first. It is best if possible to use the mains power when you are using your macBook and only use the battery when you cannot connect to mains.

MacBook batteries have a life span based on the number of charge cycles the battery has been through. The battery has a max of 300 cycles before it starts to loss its charge capability. SO you need to determine the health of the battery is it chargeing etc. You can do this via the apple menu and 'about this mac'

http://support.apple.com/kb/HT1519

Check the health of the battery as the battery could be faulty if it has only cycled a few times or it may have gone over the 300 and is now lossing its charge in which case you'll need to get a new one.

Hope that helps

Paul

SOURCE: macbook says it is not charging but plug indicates

This usually means that your battery is not holding a charge anymore. You will have to replace your battery. A cheaper route is to keep it always plugged in.

SOURCE: the fan on my macbook

The green light on your power adapter is normal, this indicates that it is charging the battery. The fan within the MacBook is controlled by an internal heat sensor. The fan inside will speed up and slow down based on the internal temperatures.
The X icon for where the battery is, indicates that the battery is not connected or the system doesn't recognize the battery anymore. Meaning, you will need to buy a new battery for your computer.