Hi all,
First post here so I hope I'm in the right area.
I searched a bit but could not find a similar question, but sorry if this is a dupe.

I have an old laptop with a shoddy battery so I bought a new battery. It is a generic replacement, all the voltage and ampage numbers are the same, the replacements claims to be a right match for the old one, and the models all match. By rights, as far as I can see, it shold just work.

Windows reported it was 75% when I first put it in with charger and it is now at 100% (5 hours plugged in). BUT pull out the power cord and suddenly I have no power.
Battery seems to not exist without mains power.

Should I keep charging or do I have the wrong battery or a bad battery?

Thanks for any advice