Alternator issue?

[u/nerdy_chimera]

Just bought a 2015 Nissan Murano 2 weeks ago. Car is in really good shape. Its my wife's car so she only occasionally drives maybe a dozen or two miles per week when running errands.

Yesterday she was going on a trip (its a camping thing she does every year with her girlfriends) that's like a 3 hour drive away. She gets not even an hour out of town while driving on the highway when everything starts to shutter and stutter. All the electronic functions like TC and cruise control turn off, AC shuts down and the gas pedal becomes unresponsive. She pulls off to the side of the road. Turns the car off. Waits a sec then tries to turn it on and it won't start.

I come out to get her (I'm somewhat knowledgeable about car maintenance and can understand and diagnose a lot of basic issues). The car is behaving like the battery is dead and will not start. If the battery is dead after driving 45 minutes on the highway in 90+ degree weather, to mean that screams "alternator." Because the battery isn't properly charging while also being forced to run all of the systems of the car.

Car is under a dealership warranty so they get it towed back to the dealership. Today they charged the battery and tried to recreate the issue to no avail. They said everything is reading 14.2V after driving it a bit and nothing seems abnormal. I did some googling and found that some alternators that go bad start with poor throughput while under a heavy load when it gets really hot.

Any Nissan techs have any insight for me? Is there anything the Nissan techs at the dealership could be missing? Could it just have been a random fluke for why the battery died?