Mechanic replaced my battery, he placed a 790cca instead of the 700cca.

Need to know > where did this pop sound come from? .. Under hood?

Hello, the popping noise could be related to something possibly not being hooked up properly? The alternator typically doesn't just fail like that; an instantaneous failure that you describe along with a popping noise could be a maxi-fuse (high amperage fuse) popping because the battery cables may have been installed in reverse. This is just an educated guess. Have a trained technician test the fuses in your under hood fuse box, and I bet you'll find one is compromised. Besides that: there could be a secondary problem in your charging system as you've described. However, start with the known faults first before having the charging system checked professionally. You can find local technicians that can help your concerns here: http://repairpal.com/jaguar-within-10-miles-of-fayetteville-georgia-30214