Samsung Np350V5C-A0BUK battery issue

The problem started a while ago when my laptop started not turning on unless the charger was plugged in, so when it came to using my laptop I would just use it while it was charging, I should have bought a new battery when this started but I never got around to it.

So today I went to turn on my laptop as usual and it wouldn't turn on and no lights would show, so I tried a different charger in case it was a damaged lead but it still didn't turn on. I tried removing the battery and holding the power button for 30 seconds but nothing, then it would turn on and I would hear the fans running and it was come up with the Samsung logo but then shut off straight away. Now its gone back to not turning on at all. Is this an issue with my battery and all I need to do is buy a new one or is it something else?

Thanks