Thor generally uses WFCO converter/chargers in their lower-end products. In the Axis/Vegas coaches it has been the 8945. Can't say this will be true for the ACE.
The WFCO chargers are three-stage (bulk, absorption, float or trickle), but there have been lots of reports that they do not switch from stage to stage reliably. They either bulk-charge too long and cook batteries or don't go into bulk-charge at all and the batteries never get fully charged.
Replacing the WFCO with a Progressive Dynamics is on my to-do list.