2018 Suburban Battery Drain/Bad

[Andrew Pennington]

2018 suburban 

 

battery tests good 

 

alternator tested a bit high at 15.2 volts under no load 

 

The cars cranks great, charges a bit over 14 on gauge. 
 

Randomly after starting fine for days or weeks, and most recently after shutting the car off for about 5 min, and then restarting, the battery will be dead. Showing only 9 volts on gauge. 
 

When you jump it, it fires up instantly. No need to wait or rev the other vehicle. Like a brand new battery. 
 

Then repeat the process. Days or week and it does this again. No signs or symptoms just dead battery seemingly instantly.

Could this be an alternator issue?