No power to vehicle

I have not driven the car in a while, the battery it had was old and it would not start without a jump so I swapped it out for another one I had laying around and it started fine. Drove it around for a few days then left it there for about two weeks. I tried to start it it clicked then all the power to the vehicle turned off. I have tried checking some the main fuses with a tester and they all seem to be fine. Should I just go get another battery and try that? I think the battery I have on it now does not have the correct specs for the car. I have tried hooking the car up to a battery charger and the lights turn on but everything is dim and slow to light up. But the car has no power at all without it being hooked up.