My alternator went bad and the battery
I replaced both but for some reason my battery’s keeps getting bad I replaced 4 in 3 days I got all of them and they test bad and they we’re all new
all the batteries get bad after like 50 miles

 

You most likely have a short somewhere or a severe parasitic drain. But to completely kill a battery so fast, I'm guessing you have a major short or possibly a very bad connection somewhere (loose wire, corrosion, etc.). Look for signs of melted or hot electrical wiring. An infrared camera really helps with this. If this is something beyond your skills or tool kit, take it to a professional for proper diagnosis and repair. Electrical gremlins are usually not easy to sort out without experience and access to proper tools.
-Icer

 

I agree with icer. Maybe better to take it to an electrician to get this sorted out.

 

One other suggestion: check the ground connection to the chassis (right below the top of the fender) or more importantly, check the cable-to-terminal itself. These cables rot out all the time but is overlooked because no one ever disconnects that end. A bad ground easily could be the culprit with symptoms of a bad battery or causing one because the alternator gets confused when it can't complete a circuit (or only marginally/intermittently does so).

Barring that, your electrical system is due for at least a charging system test. Alternator could be severely overcharging the battery (bad regulator) causing premature failure.