I was turning the key to start the car. Heard a fairly loud "pop" on the passenger side either under the dash or the engine bay and now there's no electrical (dome light doesn't come on when the door's open, no headlights, and of course the starter won't turn over, etc...). Battery is fully charged.

Any thoughts as to what to look for? Thanks!

A short. Fusible link blew? what car???

You say the battery is fully charged? Did you open the hood and check it after you heard the pop? I had a battery explode while trying to start my van years ago. Did the very same thing that you are describing.

Could be the ammeter wiring at the bulkhead connector.

Time for a voltmeter / test light.

70 T/A Challenger 340 with electronic ignition conversion pkg.

Thanks, but no. Battery is fine. I actually charged the battery after the lights didn't come on. It's charged and still no power.

I'll be giving it look! Thanks!

Yeah... I'm kind of afraid of that. I'm no kind of electrical guy and don't really know where to start. I do have buddies that can help. Thanks!

Sounds like that to me. You may have heard the fusible link burn out which they are made to do so the wiring wont burn up if there is a short. And it can kill all power depending on which one burns out. Ron

If you happen to have any 12V bulb/socket with a pair of wires coming out of it (pigtails) laying around, just bare the insulation off of each of the two ends & ground one end to bare metal on the firewall and wrap the other bare wire around a thin metal probe & stick it in the bulkhead terminal where the main power lead goes in (trace the power from the batt positive lead to the starter relay & it continues on to the bulkhead to that particular terminal). if no light then the FL has popped, if it lights then the open is under the dash (the 2 bulkhead halves coulda lost continuity in that particular male/female brass terminal connection between the two bulkhead halves there on the eng side of the firewall but not likely). if it is the FL then NAPA has a replacement for cheap & I would have someone crimp/solder it in being carefull to wick away the heat from the soldering iron in the process. If the open is under the dash then start with the ammeter terminals as mentioned. keep us updated. EDIT batt neg cable connection to block coulda lost its connection/continuity which would render the system dead like it is but I would not expect a "pop" from that potential.

Thanks Ron!

You will definately need a multi-meter, with or without your buddies.
For simplicities sake, there's basically one wire to follow from the battery to the ignition switch. Its not physically all one wire, there are connections along the way, but that's all you have to trace to see where it burned.
There is a simplified diagram from my '67 at the bottom of this page http://www.heritech.org/cuda/Charge.html
Open your hood and see if you can follow it to the firewall connector. If the fusible link failed, it will literally be melted away. That's its job.

If it didn't then almost certainly something else was the weakest link and failed. Look between the firewall connector and the ignition switch. Thats a little harder for the switches in the steering column. But if you need the wire color, it will be in the '70 shop manual. Most likely black or red at least to the main junction.

Next you need your buddies with the multimeter. Because something drew too much power from the battery. Most likely a bare wire touched ground, and most likely one that is not protected by the fusebox.

This will help me a lot and get started! Thanks Robert!!

Thanks Mattax! I'll be getting on it!