Help, car keeps dieing

Get a cigarette lighter voltmeter. I got several for $3 on sale at HF and put in all my modern cars that have poor charging diagnostics. I especially use them on long trips so I don't get surprised by a no charge situation. You should read ~12.6 V off and ~14.3 V when running, if the alternator works.

I also have a Black & Decker battery charger that has an "ALT Test" function. It just looks for sinusoidal fluctuations that are typical of the alternator output. It was cheap at Big Lots, and is small and light.