Even 3 years can be old for a battery. Were the battery cables replaced 3 years ago? You would be surprised how many electrical issues were caused by a bad ground. Have both cables at least checked for corrosion and resistance.

More proof that it could be the battery:
https://www.hyundaiforum.com/forum/s...ead.php?t=9131

That is an interesting though. I haven't seen traditional signs of a battery problem; slow starts, dead when not used frequently. Nor, have I done bad battery things like leaving lights on and killing the battery. But, thinking of the battery shorting internally, that could do some interesting things to the electrical system.

Hopefully tonight it will work for me to jump start it and charge it up and see how things are operating. It will be particularly interesting to see if the headlight switch sticks in the same state where a relay or something was firing repeatedly when the key is out with headlight switch in on position.