Bellbear,
Re the charger:
by way of explanation, I only brought up the charging voltage because at that time the single battery voltage was in question yet the batteries seemed to be have been successfully re charged with a home charger. That brought to my mind the older, automotive chargers I am most familiar with that were either 6v or 12v nominal output. Or some units could do both, but one voltage needed to be selected to use. Sorry if this muddied the waters.
Your charger should be marked with it's output voltage (label?)
And I should have specifically asked or followed up on how exactly you had charged the batts - singly or connected together (if connected, how).
Re the battery voltage.
I should have mentioned that, from what I have gathered, in a camper with 2 batteries, using a 2 x 6v format is commonplace, even to be expected and, some have said, generally better than a 2 x 12v format.
Although you may not remember the exact wiring, you may remember if each battery post had only 1 wire connected to it ?
Everything but the thread title (which prompted me to chime in) suggests the batteries are 6v. Which would mean they should be wired in series as show in my 2nd post. The previous owner may have meant the camper system is 12v, incl the "battery bank" as opposed to the individual batteries.
If in doubt about the battery condition/usable service life, an auto service or battery shop should be able to test them.