I got a replacement battery, reset the SMC, and my computer will still turn off unexpectedly.

Early 2011 15" Macbook Pro, 2ghz iz, C0*****F8V.
My original battery wore down to the point where it would not be recognized as available and the computer couldn't power on without shutting down in a few minutes. I ordered a replacement battery, certified Apple genuine, but after 3 days it reached about half charge and the computer died, not turning back on without the adapter. When it did reboot the battery was at 0% and not charging, and the computer was incredibly slow and laggy.
I refunded and returned this battery and got a new one. I've had it installed about 2 days and the computer will still turn off if not plugged in at about 80-85%. I have reset my SMC multiple times and my PRAM as well. coconutBattery says nothing is wrong with the battery.
What can I do? I'm a freelance video editor and this is basically calling me out sick from work for a week now.
<Personal Information Edited by Host>

FinchDrive wrote:
I just finished running the AHT and an extended test. Hardware error pointing to the battery on both:
4xxx/40000005: "Battery"
and 4xxx/4/40000005: ◊òä "Battery"
upon the extended test.
Do these codes refer strictly to the battery, or to possibly other components that interact with it?
I can not give you a definitive answer to that.  The 'x's' which I have marked should be letters.  If so, could you provide them and that may give us a clue:
If that is actually what was generated by the AHT, then I am a bit surprised.
At any rate, the bottom line is that the MBP does not like your battery even though the output information that you provided does not indicate anything adverse.  An Apple battery should correct your problem, I would think, but there is an alternative that I came across yesterday that you might consider.  OWC. a Mac oriented vendor, is now selling replacement batteries for MBPs.
Based on the reputation of the company, I personally would be willing to try their non-Apple branded replacement.  I have dealt with them a fair amount, so my statement is from experience.  Note that is has a 1 year guarantee as do the Apple batteries.  ( I will need a replacement for my 2010 MBP and I will probably purchase it from them)