I have wondered about this myself in the past. I installed a PD4645 4-stage converter a year ago and have it feeding a single 12v 80ah battery.
My converter stays in absorption mode at 13.65v until the Trimetric has been showing 0.00a to 0.01a for around 12-24 hours.
My understanding is that the 13.2v maintenance mode is just that - it won't drop to that until the battery is 100% charged, and 13.2v will then maintain 100%.
It makes sense to me since the old single stage chargers use to run around 13.6v, and I'd only run it for a few days every month or so to maintain the charge without boiling the batteries.
