mac Book air shows abttery loaded 99 % but still needs to plug the chager hello Iread so many things. it seems no one faced my situation. 
my mac book air battery is loaded at 99 % but if I disconnect the charger mac book closes

before that, it often happened that randomely mac book air closes and to restart again i need to plug with charger. when I check battery it was loaded generally around 50 % 

who can help me ?
thank you
This is typical when a lithium battery fails. You could buy a new battery or take it in for service in the unlikely instance that the charging circuitry is what has broken. Batteries are designed to fail and are consumable. The circuitry is far less likely to fail, but you can't tell the difference without servicing the hardware.

You can learn more at http://www.apple.com/batteries/ and perhaps see what your full charge cycle and other batter information show - that would perhaps reinforce the notion that it's time to get a battery replacement.



The System Information app can show your your power measurements.