So I found a possible software issue with my Montana 700 (non-inreach) that I'm hoping can be fixed in a future software update, and also a workaround that might be helpful if anyone else experiences the same issue until then. I bought the AA Battery Pack was finally available in late January and on the first cold-weather trip I used it on, starting out with a fresh pair of Energizer Ultimate Lithium batteries, after literally ten minutes, it showed the batteries were at half life, another 5-10 minutes and it warned of low batteries and then shut off completely. I tried another set of batteries and same thing, then I tried the "dead" batteries pulled from my 700 and put them in my friend's older Montana 680 and those same two batteries lasted for three more full days at cold temps!
After the first set of batteries "died" and I put another set in, I checked and found that once you put the AA battery pack in the device instead of the standard brick battery, it enables a few extra options under setup>system>battery type: "Alkaline", "Lithium", "NiMH" and "Precharged NiMH". I thought it odd that "Alkaline" was preset by default even though Garmin recommended the use of lithium batteries with the battery pack. With the device now showing half charge on a set of lithium batteries, I changed the setting to "Alkaline" and then it showed full battery life and I was able to get a normal couple days use out of each pair of batteries. I have been leaving it set to alkaline while using lithium batteries and have had no other issues.
I suspect this may be as simple as the terms "Alkaline" and "Lithium" being superimposed in the settings menu, and hopefully a software update in the future can fix it. This could have been a very serious problem for anyone who may have become lost in remote wilderness and unable to find their way because all of their brand new batteries "died" after 20 minutes or less of use from each pair.
