At 10.4 volts your batteries are virtually dead, (probably not getting a charge due to bad cable). Your converter may or may not charge them up overnight depending on battery condition/age etc. If you have a stand alone battery charger, it maybe a better option to recharge them.
Even if you get them up to full voltage, it would probably be wise to have them load tested. My 06 Winnebago Outlook c-class probably has the same converter as yours. Mine is plugged in at home, 12 months a year, when not being used and batteries turned on always. I just replaced the 2012 batteries this past June.
Ken
