Dear Beadsandbeads - Your reserve calulation is interesting. I expect the battery gradually lost ground after many weeks because my wife usually makes short trips with the car. On her last trip, as I mentioned, it just couldn’t crank the engine again. That fits with your reserve calculation at least in a general way.
Ammeter Calibration – Good idea – I’ll go to Radio Shack, buy a resistor or two, and double check the calibration of the meter at near this current level and on the same scale.
By the way, I did a side-by-side test with my two cars the other night. First I topped off both batteries with a trickle charger until there was almost zero charging current draw for both batteries. Then I let both cars sit overnight (about 10 hours) with the key off and no charger. Then I put the trickle charger on each car, one at a time. The Buick needed only a brief surge (1/4 scale) of current in about TEN SECONDS the charger’s ammeter was back to virtually zero . Then I did the same with the TrailBlazer. The TrailBlazer pulled the charger’s ammeter fully to 1/2 scale and it took over a half hour to get it gradually back close to the “zero” level that it had showed when topped off the night before. This is an indirect indication, but pretty strong evidence that there’s a whole lot more parasitic draw on the TB than the Buick.
Thanks, Dave