All laptop batteries are created equal by Their Maker. But even so, some last longer than others despite coming out of the same production lines. Why? Because although it is manufactured to last (say) 5 hours, sometimes you only get 2 hours before it dies. Usually that means that your actual capacity is lower than what it was manufactured to be.
Here’s how you can figure out how useful your battery really is:
install acpi if it’s not yet available
sudo aptitude install acpi
Open a terminal / console and type:
See those details? Thats some minimal details available. Now for a more detailed view do this:
Look at the design capacity and last full capacity:
If you’re last full capacity is under the design capacity, then your battery cannot store as much power as it should and will therefore die faster than it should.
If the last full capacity is under 50% of the design capacity, I’d consider getting a new one.