I have an HP dv6-6173cl. It's just old enough to be out of the 2-year warranty.
The battery was not holding a charge for long, so I bought a new one ($20 eBay). I did the full charge, discharge cycles. But, when fully charged, if I let drain down to anywhere from 90-50%, the laptop will power-off (not gracefully, it just blacks out).
So I bought a new battery (Ubatteries, also from eBay, $30). Installed the battery, let it charge overnight, turned it on this morning. I played a game online for 10 minutes, got down to about 90%, and poof, computer shuts off. Turned it back on, played for a few more minutes, and it turns off again.
I booted into Safe Mode, and ran some activities (Malwarebyes scan, etc), and the battery seems to be lasting a long while (though there is no battery gauge in Safe Mode).
Does this sound like laptop issue? Maybe the OS (Windows 7 x64 Home Premium)? Two defective batteries, or problems with their being non-HP? Is there some was to "wipe battery stats" or something (like on Android)?
Replace the CMOS battery on your laptop's motherboard and also update the BIOS. If that doesn't resolve your issues, then I would recommend to just buy a new laptop.
I reinstalled the original HP battery. Though it doesn't hold a charge long (half-hour while playing an online game "Robot Attack"), the laptop does not spontaneously turn off. It only does it with the brand new aftermarket batteries.
I'm not sure where to go from here. I'm going to order a CMOS battery, and see if that helps.