Yes...correct...STEADY STATE VOLTAGE is a good indicator of battery condition. Now please explain how when living in your coach and using electricity...the necessary UN CONNECTED time to record an accurage voltage may be obtained.
VOLTAGE readings in a operating coach/trailer tell you one of two things accurately...your battery is being charged...OR...your battery is dead.
It is neither an accurate reflection of the state of your battery, the capacity remaining, the amp HOURS remaining at present use rates, OR the 50% point when you better recharge if you don't want to lose cycle life.
When you can SEE and know the currrent draw of your heaters and KNOW that you have enough capacity to last the night you may sleep soundly and warm. Otherwise...you know to run the genny before going to sleep OR that you better add battery capacity if you want to stay warm in the future.
I repeat...VOLTAGE meters are cheap unaccceptable substitutes for REAL battery monitoring and preservation for those who boondock.
Now...if you want to know the STATE of your batteries...charge them fully...disconnect the negative wire and WAIT 24 hours before taking a reading
at the terminals...or use a turkey baster in the same manner to take a spec grav. reading. THAT is a steady state reading.
Anything below 12.6V says capacity diminished. Anything below 12.4 says capacity significantly diminished...start saving for new ones. Anything below 12.2 says install new ones if you're gonna be camping dry.
As an analogy to water, water-flow like amps, tells you the flow rate, but does not tell you potential back at the reservoir (which is voltage). You can get 10 gal/min from a 55 gallon drum and also from a reservoir. But you need to know the potential of the source (tank), which is voltage.
Nice try. You might actually want to read the manual from a Victron or Trimetric before you tell us about water and reservoirs and what you need...and what YOU don't have....and are deep cycle batteries rated in volts or amp hours???? Wonder why that is???