Car won't crank!!, What could it be? Options

[cyb593]

So here is the scenario. I recently just got my O2 sensor changed on my 1995 Toyota Celica GT . I bring it home from the mechanic due to an oxygen sensor being unremovable on my part. I drive it home just fine and park the car in my driveway. I only live about 2 miles from the mechanic. Two days later I try to crank the car in the morning and it won't crank it starts making a small clicking noise and the light flashing on the dash.I have already replaced the battery back in January when It went bad. Meanwhile 1 week later I try to jumpstart the car and it won't start. I hook the battery up to a battery charger get all the way charged up reconnect the battery. After I do this the car tries to start up for a second then stops then all the lights on my dash go dim no matter if I'm trying to start the car or not, they are maybe half the brightness they should be. Meanwhile my alarm system starts to go off even though all my doors are closed and my hood is closed and the alarm was only going off about a fourth of the sound level that it should. I was thinking alternator at first but now I am just dumbfounded what could cause this problem. I do have video of it trying to crank the morning this started.

I also got a new viper alarm system installed by Best Buy before Christmas, the battery changed in January. Could there be a problem with the alarm system? Alternator? Starter? Battery connectors?

Any help would be great and anything you think I need to provide such as a video or pictures I can do.

[Box]

Yeah that's right 6x2.1=12.6 total voltage, guess I should've said weak instead of dead. With no load it's fine, but once under load it rears itself. Either way I'd test with a battery that's known to be good, you have two other cars in your sig surely between the two you have a battery to try. Easier than going to have the battery tested when this will tell you definitively in about five minutes.

This post has been edited by Box: Jun 11, 2016 - 9:35 PM