Plug in at home and see if your 12V stuff works.
You should be fine, UNLESS the battery is so bad that it prevents the converter from charging the battery...and that is what gives you your 12v source when connected to shore power.
The battery may not be able to get back to full capacity, but you can likely still operate on shore power.
2014 40QBH Phaeton DP Cummins 380HP ISL, Freightliner XC, 2014 Jeep Trailhawk TOAD
Blue Ox Aventa tow bar, SMI Air Force One -South Orange County Ca.