I HAVE A LAPTOP N76VZ I just bought a new battery i have using without a battery for while but when i use the baterry it randomly turn off (like loosing power) and it work fine without a battery without any problem. the battrey is new and it fully charged and also charging normally when i plug the AC adapter.
You need to check your power options in control panel. You will find that there are two options one for battery and one for plugged in.
You need to change your power plan setting to match those to plugged in. Also check advanced power settings i.e if your hard disk is idle or other device is idle your laptop will be shutting down to conserve power to save you from suffering a total lose of power in an instance which could cause you a bigger problem damaging windows and other software files.
Myself I leave everything turned off in my power options as use it very little on battery you should however allow it to turn your laptop off when the battery reaches 10% charge this will make your battery last longer in the long run don't allow it to run down completely as this will cause it to struggle on changing and make it die before its time. Some batteries will not recharge if allowed to run down to completely.
If you can leave it plugged in and every 6 weeks or so run down to 10% charge.