Hey for whoever ends up on this thread - I ended up having to replace the battery again after it degraded again due to the fans not really cooling the laptop. It boots just fine from battery now so issue was the battery - the new one has the 1" square metal pad at each end that neither of the replacement batteries I had tried before had just like @trainguy mentioned. I had used something that claimed to be an OEM HP part last time and this time just got the cheapest thing off of amazon, YMMV.
