I think those old Magnetek standalone chargers were single-stage. It possibly could have two stages with one being a float, but I seriously doubt it has the three stages needed to maintain healthy batteries.
If single stage, these have been known to boil batteries if not watched closely and replacing a Magnetek Parallax with a better one is easy to do if you are concerned.
So, first thing is just verify if its single stage or not. I think it is, but you should double-check.
BTW Is something going on with the charger and batteries leading you to ask the question?
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD