OK, I think my problem may be something else...
This morning my 80 would not start after sitting all weekend. I put the trickle charger on it, and left it for the day. It was a very nice day for driving my topless 40 anyway.
I bought a $20 multimeter from Sears. Tonight I did some measurements:
Battery with vehicle off: 12.34 v
Battery with vehicle on, idling: 14.56 v
Battery with vehicle on, headlights on, car stereo blasting, A/C on super cold with fan blowing on high, idling: 14.55 v
So I'm thinking that my battery is probably OK (it's an Optima red top, only 1 year old). And I'm thinking that my alternator is doing its job. So something is probably drawing current when the vehicle is off, and now I need to discover what it is.