Good evening folks, new here and I'm at my wits end.

I have a 05 Suburban that the battery drains and has for some time now. I have nothing visibly causing the drain. I have purchased two new batteries. With each battery I get one full night out of it, then it's dead in the morning. Once I charge it back up and use it, if I don't disconnect the positive terminal when leaving the vehicle, it won't have enough voltage to start after an hour or so. The alternator is charging the battery sufficiently when running. I am showing 14.5/14.6 while the car is running.

I have tried checking for am amperage draw when the vehicle is off, connecting the multimeter i series to the negative side but I can't get any reading. I have tried both pulling and testing each fuse with no results.
I installed plug and play LED headlights on the vehicle at least a year ago and this battery drain has only started in the last 6 months. I have disconnected the headlamps and left the vehicle overnight and it still drains.
I have just discovered that the alternator can allow me for a drain but I'm not sure how to test it. Can I just take the connection off the post of the alternator and leave it overnight to see if the battery still drains or must I disconnect something else from the alternator to check?

There's been absolutely no explanation whatsoever why my battery is draining so quickly and it's far too cold to be standing out there with my wrench disconnecting and reconnecting the battery every time I stop and start the vehicle.
Thanks for your help!

 

Did you ever find the culprit of the battery drain?

 

That's what I'd try first.

If not that, read up on parasitic drains and start pulling fuses one by one to isolate where the drain is.