If you lost all power then I would start at the battery terminals. These can get a film of corrosion between the posts and the terminals. Test continuity with a multimeter or clean them up and refit with a smear of dielectric grease. If no improvement check the main earth terminal.

Sorry, it's all I can think of right now.

 

as dane said,
if you not getting any power to lights/radio etc, check terminals,
if you have power to lights/radio but nothing happens when you turn the key
not even a click on the starter, try to check starter terminals, its a tight fit to get in, from right side of engine bay have to squeeze under manifold, will get bruises on your hand,
while changing alternator may have left a loose connection

 

Need to check the basic stuff first. Total loss of electrical power is an indicator of poor connections

1. Check all fuses in the PDC. Check for any blown or loose fuses
2. Check for 12v at the battery using a DVM (Digital Volt Meter)
3. Check all chassis grounds
4. Clean all connection and check for any broken or loose wires.

 

I've had a similar problem just this morning. It may be your keyless entry system. There is a fault whereby in cold dry weather static builds up in the key and can cause the system to cut out. There is a tech bulletin at wkjeeps.com/misc/Patriot/TSB/tsb_0800708.pdf that shows the details and repair solution. A temporary fix is to remove the Wmc IOD fuse ( I think its number 17 in the fuse box) wait 30 secs and replace. That'll get you home but you need to have it checked over in a garage which is what I'm off to do now.

 

any news on your issue?
i have something similar.
started a thread in "electrical"
http://www.jeeppatriot.com/forum/showthread.php?t=111943

 

I have a 07 Jeep Patriot that is having some electrical problems, not sure what though. Went to the store and it drove just fine, no issues. Left from that store and went to another and my key fob would not lock the doors. I tried cranking my car and nothing, no click, no lights, nothing. I went inside Walmart waiting on someone to come, I spent roughly 20 mins inside and when I came back out it started no problem. On the way home the ABS, Brake, ESP BAS, and Traction control lights were all flashing. When they would flash my speedo would fluctuate and my Patriot would act like it was dying. Twice on the way home my radio lights turned off and back on. Looked at the fuses, checked the battery, alternator is good and starter so I’m not sure what could be going on. Anyone have a similar situation or know what could be going on?

 

I'm experiencing the exact same issues on my 2013 Patriot. Were you able to diagnose the problem on your vehicle? Any insight would be much appreciated. Thank you.

 

Check the relay box under the left headlight/battery. It's been known to corrode and cause issues.