mmlee Mark you forgot the ignition systems, what are you running?? MSD??
First off the gauge in the car is only ball park for reading the charging and draining of the electrical system. I don't know if you have under size pulleys from March?? This will also slow down the alt for charging. You need to get a cheap voltmeter and use this to check the charging system. The battery should be ok. A load test at a gas station needs to be done. DON'T let the guy sell you a new battery or ALT. Alot of stores have bad testers that fail about 20% of all batterys that there is nothing wrong with them. The trickel charger is working just fine. Once you get your volt meter. you can do 3 easy tests
1 With the car off check the battery volts. Turn the lights on for about 10 second to level out and charging the battery just had. readings should be in the 12.30's to 12.50's this is a full charged battery
2 start car and let it run for a minute at idle. No acc to be on. record voltage of charging system. should be in the 13.7- 14.20's voltage readings.
3 load charging system with fans, lights and blower motor, check charging numbers, at idle. Should be a min of 12.7volts or higher
4 Rev the motor up to 2,000 rpms and check the voltage with the same load. You are looking for a 13.7 and higher.
If all these check out, the charging system is fine. The battery can only be tested with a load tester.
You have to remember that the ALT when the car is running is suppling power to the electrical of the car plus recharging the battery at the same time.
This is way Volt gauges are better than Amp gauges. Also the charging systems have gone from 6 volts to 18 volts and have 300 amp alt's. Enough to run your house.
Do the check out first then get back to us. The only failure could be a weak voltage regulator or a diode bridge going bad. Make sure connections are tight on battery, back of Alt, and voltage regulator. Check the grounds for being clean and tight. That's all there is for charging system check 101.
Rick L.