Haw can I tell if my laptop's instability is caused by the power supply?

Hamdeath

Estimable
Jan 31, 2015
17
0
4,560
Hi everyone,
I'm having lately graphic card crashes and low internet and I think this is caused by my power supply (it may be damaged).
So haw can I tell if my laptop's instability is caused by the power supply?
Thank you.
 
If windows shows me this error "there is a problem with your battery so your computer might shut down suddenly", can that mean the battery isn't giving good voltage or it has nothing to do with it?