If you have a volt meter then you can take some readings and post and maybe get a diagnosis. You would want to measure the battery voltage at rest (car off), at idle, and at 1500 or so RPM. Also you can check your connections by measuring the voltage from one side of a connector to the other. For example from the clamp to the post. You would want some load to make some current so you could turn on the lights to do that test. You could do that test with the car off.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra