Battery draining while driving and the car shuts off

Hello,

This could be due to a faulty alternator.
If the alternator is not providing proper output to the battery, it will cause the warning light (usually the low charger or battery light) to go off. This will discharge the battery and as soon the battery is depleted the engine will shut off, usually when slowing down or coming to a stop.
Typically, a good alternator will put out 13.6V -15.2V to the battery with the engine running.

Here is a helpful guide on how to test the alternator:

https://www.2carpros.com/articles/how-to-check-a-car-alternator
https://www.2carpros.com/articles/how-to-replace-an-alternator

I have attached diagrams below for your reference.

Let me know of any questions.
Thank you.