No power

sounds like a alternator starting to fail,also replace battery if 4 years old or older,but it sounds like the bad alternator damaged the battery.

The bad part about running a modern car without a battery is that any variation in draw can cause either a spike or a drop, with a spike being a potential electronics killer. The alternator alone cannot keep up. I'm pretty sure this car has a battery maintainer module too. So at this point, you have to look through the entire battery harness, ignition and starter circuits for any problems. Get the battery load tested somewhere, you'll need a good fully charged battery to do any real testing. Once a battery is hooked back up look for voltage drops to the major components like the starter.

The alternator covers all of your electrical components and charges your battery. The issue is that your car has a voltage regulator. so, when it's charging the battery the voltage regulator has the alternator current output higher. when you disconnect the battery it takes a millisecond for the computer to adjust the current down to where it needs to be. (power surge) unfortunately, a millisecond is enough to fry components like the ECM or PCM. proper diagnosis of these items is difficult and if you make a mistake, you my fry the component if it wasn't already. if your able to get ahold of the diagnostic tree for that item that would be best. make sure you read instructions and notes