Larman
I'm catching up and just noticed your post re MS Battys.
I had some issues after purchasing our MS34HT used.
Here is a link re: what I found and installed as an improvement. My biggest finding & concern was the diode isolators MS installed. Eliminating them was a primary objective.
https://www.trawlerforum.com/forums/s11/ms-34ht-charging-system-mods-24228.html
I agree (as always) with DavidM. I went a slightly different path than he outlines, however, and I am currently contemplating what to replace my current AGM 8Ds with when the expire. I lean towards 6V GC AGMs instead of FLAs as I store the boat on the hard for 7 months +/- and have no charging capability during storage. The factory 8Ds were next to impossible to remove / replace each season so I decided the premium $ of AGMs was necessary. My unanswered question is whether it is worth the trouble and expense of separating house from start as MS has them tied together. I'm also undecided at this point whether to go with deep cycle or start battys for the thruster bank, but that's a different discussion and don't mean to confuse your topic. I have monitored battys each spring after unwrapping and track V. The objective seems to have been satisfied as my AGMs are always at around 12.6V after the 7 mos of storage. I would not expect the same with FLAs
I moved my CO detectors from always on (bypassing the batty SW) to powered via the atty SW to avoid that drain. My feeling is that battys will only be shut down when I'm not aboard and I don't need CO protection in that case.