Temperature sensitive parasitic battery drain

[bjarriel]

First, I am new to posting here so please direct me or this post to the correct place or to previous posts if appropriate.
Second, my issue: My 2001 7.3 PSD has a parasitic battery drain, but it seems to be temperature related. I have performed the regular fuse and relay check and found one relay that needed to be replaced. Helped but not a total fix. In my location in Alaska, we are just at the mid 60 degree temperatures. During colder weather (below 40) my battery looses about .8 volts over night. Around zero degrees, I lose about 1.1 volts over night. However, above 65 degrees, my voltage holds consistent for days. Now I am aware that as batteries get colder, they become less effective. I use battery warmers on both batteries when below 30 degrees. I have also just replace the GP relay - helped some, but still losing voltage when nights drop below 65. Iam confused why temperature plays into this.

Are there any relays (or anything else) that are temperature sensitive that might be drawing power on cold nights?

Only thing added to the stock truck is:
1. my RV brake controller which, while trying to diagnosis this I have disconnected.
2. Auto starter which to be working fine.

Thanks for your suggestions and help

[ianstew]

how old are your batteries?

[bjarriel]

Oops. forgot that part. They are about 8 months old and load test fine.