No code, but Fatal exception (0): epc1=0x402066ac, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000 in Serial Monitor I have a Wemos d1 mini, and when I upload nothing or anything to it, the built-in LED always lights up and the serial monitor gets a lot of garbage at every baudrate.  I have supplied it with 4 AA batteries and the board has a built in voltage regulator of 3.3V at the 5V pin.  

The Wemos d1 mini contains the esp8266 chip.

Please help me!  I have searched everywhere.  This just happened all of a sudden, the board was working perfectly fine before too.
Three words.  "You Bricked it"
Before you go surfing on the web for days and days, I'm just going to say the module is bricked.  I've been there and found out that you should never use these devices on breadboards and with funky power sources.  There is this chip within the module called eFuse,  which is basically an electronic fuse that's really easy to destroy.  Just use the Arduino YUN or other certified or Chinese clonable modules. Those Italians are smarter than you think. That's probably more reliable because you won't have any power issues or frying issues.

I'm also assuming that you are getting a fatal exception (0) in the Serial Monitor.  In that case, your module's death sentence is officially sealed.  

Congrats. :(