Starting Charging Issues

Monday I was driving my 2013 CM and the radio was turning off and on and all the lights were lit up on the dash, I stopped at the local auto parts store and turned off the truck, I tried to restart and everything was dead, I had the battery tested and was told It had a bad cell (Original Battery).
I replaced the battery with an Red top Optima.
Today I went to a job site got out of my truck for 5 min. Came back everything is dead no power to any accessories and it won’t start. I hooked a jump box to it and it fired right up. Drove it 35 miles home, if I had any accessories on, the dashboard would light up, if I turned off all unnecessary accessories all the lights would go off.
Took it to advance auto they hooked up to their diagnostic equipment everything checks out fine.

I’m leaning on replacing the alternator, any other ideas maybe it has a diode or regulator that is sporadically failing.

 

I would first start by making sure your connections are good and clean.... If these are good then I would look into checking your grounding point, or even replacing your ground cable. I get dead starts every once in a while and it turns out to be loose connections, or battery shifting which is the same difference, as I've misplaced my battery retainer, due to replacing so many batteries, lol.... The biggest thing is the connections in my opinion you will have to sort of charge it for 30 minutes which may include maintaining the idle higher than 1k with the throttle for a little bit and monitor... I go through this ever so often and have to take the battery to get charged as well....