1997 Ford Explorer charging system

Go to this link: https://www.2carpros.com/how_to/how_to_test_alternator.htm

Have you checked your voltage regulator?
Check the battery voltage before and after starting the engine to determine if the battery voltage increases. Refer to the Normal Charging System Voltages chart.

Normal Charging System Voltages
Terminal "A" "S" "I" "Alt B+" "Batt"
"Eng to bat grnd"

Key OFF (12V) (0V) (0V) (12V) (12V)
0V
Key On - Engine Off (12V) (0V) (1-3V) (12V)
(12V) (0V)
Engine Running (12V- 15V) (6-8V) (12V- 15V) (12V-15V) (12V- 15V) (0V)

If you have an "Advance Auto Parts" near your location they will check your Alt. - Battery - Regulator and let you know what's going on.
Good Luck;
Rick