Apple - Taking battery out of my MacBook Pro

There is no way to remove the bettery without losing the warranty for your Macbook. Simply unplug the battery charger should do the trick.

If you want further information on how to maintain battery life, Apple is providing a useful page.

Every time we unplug the power, the Mac will start to discharge the battery. In this manner, the battery lifespan will shorten.

The answer would be to leave the charger on whenever possible, as the charger actually stops charging the battery once it is full.

Check this on your Mac: Click on Apple Icon > About This Mac > System Report > Power

See the "Health Information:" for cycle count and the following:

AC Charger Information:  
  Connected:    Yes 
  ...  
  Charging: No 

Here's an article discussing it: Practical Tips For Taking Care of Your Mac's Battery

I remember having read an article by Apply saying not to let the battery totally drain, as it will affect the battery lifespan. It's best to keep it around 50% and start charging whenever possible. This applies when not using the laptop for a long time - occasionally bring it out and charge it.

The battery in the new MacBook Pro 13″ is not user-accessible. Only the models of MacBook Pro before 2009 had user-accessible batteries.

The simple answer is just to unplug the charger and let it discharge. There's not really any need to keep it plugged in, unless you are performing resource-intensive tasks where the battery would be discharged very quickly and the power would be disconnected and reconnected often.