Ha, yeah, it's a head scratcher. I needed to revise some of my post above (and did) - if I summarize everything I've learned in this process, it's as follows:
- using good clamps and allowing the amp meter connection to stabilize for about 30 sec after connecting, a more accurate steady state draw can be determined (I was initially looking at the reading at a glance with pin probes and seeing a higher draw) - so the clamps and patience helped. Not sure what that initial 30 sec draw is (it's not significant, but could drain a batt if it were more permanent - approx 1+ A initially, my guess it's related to re-establishing the security system after a battery disconnect).
- with truck shut down, key out, all lights off, no accessory chargers plugged in (and with waiting for approx 30 sec for draw to stabilize after connecting the meter between the negative cable and the negative post: 60 mA drain is present, which is about normal (to keep clock alive, etc)
- with 1 ac charger plugged in (one that has a small light that glows when it's powered): 120 mA drain is present (i.e. 1 charger (with an indicator light) doubles the draw).
I've found no other drains on the batt, so I think my conclusion is this - when driving every day, the extra 60 mA of the charger equates to no impact on batt drainage - but when letting it sit for 2-3 weeks without starting, it can matter. So, I'm making it a habit to disconnect the dc power outlet connections (phone or gps chargers with indicator lights, etc) if I know it's gonna be parked for awhile. And if it's gonna be a long while, I hook up the battery tender, which is quick and painless (as long as I remember to disconnect it before I hop in and drive off, dragging the charger down the highway
)