Battery woes!!

[Patriot]

Well, you may remeber I replaced my dead battery about 2-3 weeks ago with a yellow top optima. I took the old battery to the dealer and they said the old battery was "marginally dead" and they checked the alternator out AOK.

Well, yesterday morning, I went out to find a dead Hummer...yellow top was reading 5 VDC! I jumped it and it was fine after that. No "check engine" light and no "reduced power" light.

I checked all the front grille lights for parasitic load by reading DC amps IN LINE...it read 0.00AmpsDC. I had a multimeter on it all day and it drifted around a bit but stayed at about 12 volts. I even did some quick starts and stops...still all is OK.

It sat all last week without use and was briefly started on Friday to move parking spaces...then Saturday morning....dead.

So, I'm baffled. Could it be a starting solenoid getting stuck, every so often?? A slow drain on something else?

I hate electrical intermittant problems because the dealer just scratches there head, keeps the vehicle for 3 days and says there's nothing we can do!!