No, A bad battery does not affect the performance of the laptop. What it DOES do, however, is shorten the lifespan of the laptop (and its hardware).
If you are ONLY running on battery power, and are using a battery that is:
You can potentially ruin the hardware in your device. This is because the hardware has to draw a specific amount of current (amps) from the battery. The hardware will simply overheat because the fans do not have enough power to cool the hardware. Heat will cause massive damage to the hardware over time.
Another issue that could happen is a hardware power-surge. When the battery is critical (or faulty), a power surge could happen as a result of the hardware attempting to draw more current than the battery can supply. This can sometimes cause irreparable damage to the hardware.
I have seen hard-disk and CPU failures as a result of this. The hard-disk was partially corrupted, as the lack current caused a power surge, which caused the disk heads to jump and scratch the disks.
I would suggest trying one of the following:
It you have a newer model laptop, you can remove the dead battery and use the adapter alone. Try that to see if it works on your laptop. It is best to always mention your model computer when posting a question.
That does not harm the computer but makes it a desktop replacement. Battery use has nothing to do with speed.
The answer to that depends on the system. On older systems - no, the battery won't affect speed. On many newer systems - particularly gaming systems, the answer is yes. The AC adapter in at least some of these cannot power the system at full speed. The battery IS required to run the system at full speed. That seems to be an emerging trend among systems, so the answer may be very different to someone reading this a year or more from now.
Welcome to the Dell Community @CashTad
If your laptop is a newer model, then it should have a "SMART" power system.
If your battery goes bad or is going bad it can increase the number of requests for the system to charge it.
The requests utilize the SMbus to communicate with the system.
So every time the battery requests to be charged it slows down the system.
The more requests to charge and or notifications of a bad battery, the slower the system can become.
As stated the best thing would be to disconnect/remove the battery and use as a desktop until the battery can be replaced.
A bad battery can stop a laptop from powering on.