charging system blues

You can test your battery at home, in the vehicle.Start with a fully charged battery.
Put a voltmeter on it and crank it for 12 seconds with the coil wire pulled and near-grounded, so it can still spark, but the engine cannot start. A good battery will/may drop to about 10/10.5 volts and hold there. Under 9 is trouble,probably junk. 9 to 10,charge it again,check the specific gravity, and repeat the test.