So for the longest time i've only been able to use this laptop while plugged in because it stays at 0% available (plugged in, charging) but never charges and say below there may be a problem with the battery. The thing is it does this with the original battery and the new one I just bought.
I then checked the AC adapter and it is rated at 19.5V but only reads around 19.12-19.17. So my biggest question is is that drop enough to power the system without charging the batteries?
I've also read people who have had similar problems and the fault lies on the motherboard. If that's the case how do I know? It's going in the trash pile if I can't figure out an easy fix.
That small of a difference should not make any difference. You either have a faulty battery (especially if you got a cheaper Chinese knock-off brand), or as you said the issue is on the laptop connections. You can try to reset the BIOS or try to fully reset the power by removing battery and wall power and holding in the power button for about 30 seconds.