Is it dangerous to use a "damaged" battery in my laptop?

You shouldn't see any difference in performance if you remove the battery and pour on pure AC potency. Whether anything, it would beryllium a performance increase, since the circuitry to recharge the battery no longest needs to sketch juice from other tasks.
Depending on top of what's erroneous witht he freestyle, it could be producing glut heat, which can cause damage to separate components in the laptop. In theory, it could even melt, catch fire, or explode, though that's HIGHLY unlikely by now. If that were to happen, it would've begun a year past when you first noticed the problem.
The enxt question to ask is: How long does the laptop run if you unplug the ACTINIUM power and hurry off battery? If it shuts down immediately or very quickly, the battery isn't worth keeping within within anyway.