Is it normal that the battery of a laptop is empty after 30 minutes of use?

Question is above. I know that it can't be normal. My laptop is from Toshiba and is about 5 years old. It does not charge slowly or anything, but it's plugged in all the time. Could that be the reason, why if I pull out the cable and use the laptop, without it just connected to the plug, after about 30 min the message comes "the battery is low"?

Mh, if you've connected the laptop anyway all the time you can just take out the battery. He probably broke down, because he just should not be connected continuously.

That was the case with my laptop after 2 years (only half power).
I almost always had the laptop with the battery inside. This has reduced the performance of the battery.
Remember, when he is on the power always take the battery out! However, this is not possible with some laptop manufacturers because it is permanently installed in the case! At HP, it is usually, as far as I know.

Do you have to ask yourself if you need a new battery or if you really use the battery in other places than your desk or not?

After 5 years, this weak performance is expected. Whether after 1825days and many loads, 600-1000 charge cycles are to be expected or overloaded because they last 100%.

Only if you take out the battery with about 80% and only then enter when it is needed can survive this long time.