A few months back my FJ would be dead after a couple of days and had to be jumped off. I replaced the battery, which did not help. I finally decided it must be the alternator so I bought a remanufactured one. It performed almost as badly as the original. I read that the alternator could be bad and actually drain your battery when the vehicle is off. This appears to be the case with mine. While the replacement alternator does not drain as quickly as the original one, it is still going from 12.4v fully charged down to 11.9v in 5 days. I just put in a new 250amp alternator so I will see how that goes. The question is: has anyone else had this issue? What else could I check? Also, for anyone in need of changing the 2014 alternator, there is a bolt on the back side of the alternator that is nearly impossible to get to. If you take off the driver's side from wheel, remove the bolt from the brake line bracket on the frame and bend the brake lines out the way, it is possible to remove the bolt. I did not put it back.
I think you may be completely off-base in your troubleshooting, blindly replacing parts in the hope that you will eventually find the root cause of the dead battery. You need to make some actual measurements of the electrical system to determine exactly what is going on, which will then allow you to fix the problem.
You most likely don't have a battery or alternator problem, you have a parasitic current draw problem that is draining your battery when the engine is not running. Changing alternators or batteries won't have any effect on solving the problem.
You need to measure the parasitic current drain when the engine is NOT running, and then find the source of the current draw. Remove either the B+ or ground clamp from the battery, and use a good-quality digital multimeter to measure the current flowing between the disconnected battery clamp and it's battery terminal.
MAKE SURE YOUR METER IS CAPABLE OF HANDLING AT LEAST 2A ON THE CURRENT SCALE, AND THAT YOU KNOW HOW TO SET UP THE METER TO MEASURE CURRENT.
A parasitic current draw of anything more than 30-40 milliamps is excessive and indicates a problem. The most frequent sources of parasitic current draw are interior lights that don't turn off, and incorrectly-installed aftermarket electrical accessories (radios, stereo amps, alarm systems, remote start systems, etc.).
Has anyone been modifying the electrical system lately??
If you find an excessive parasitic current draw and can't quickly isolate the cause, sequentially pull fuses until the current drops; the parasitic load will be associated with whatever circuit that fuse supplies.