With the vehicle running, I can think of anything that will totally kill the battery that quickly. I have a feeling it is either connection issue or either the battery or alternator is at fault. When this happens, do you have to have the vehicle jump started or does it require the battery be recharged?
I'm not sure what was done to check the alt and battery. However, if something is killing the battery as fast as you say and the battery is new, I'm concerned there is a major electrical issue that could lead to a fire. Do me a favor. I need you to check the basics. First, make sure the battery terminals are clean and tight. Second, follow this link for testing an alternator and let me know what you find.
Here are a few links you may find helpful:
https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked
https://www.2carpros.com/articles/how-to-use-a-voltmeter
https://www.2carpros.com/articles/how-to-check-wiring
https://www.2carpros.com/articles/how-to-check-a-car-alternator
Let me know what you find.
Joe
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Sunday, February 9th, 2020 AT 9:28 PM