Lots of potential variables when looking at a Voltage value, and calculating SOC level.
-For accurate readings, the batteries should 'rest' for ~12 hours with no drain/charge going into them, before taking a voltage reading. A Multi Meter reading at the battery itself, is the most accurate way to measure.
-Current battery temperatures should be factored too. The measure voltage can be adjusted up, if the batteries are at low temperatures, or down if the batteries are at higher temperature. (Look for spec's for your specific battery manufactures, on temperature compensation values. And keep in mind the 'mass' of some battery banks, even two batteries have a pretty good mass to them. So even if the outside temp in the AM has warmed up to say 65 degrees, the batteries could still be much cooler (Reverse if it was hot, and now cooler temps:)!). (For example, we have X's 4 L16's Lifelines. Took a reading today, after a 14 hours 'at rest' period. Outside temperature was 68, but the Magnum Temp Sensor reading reflect battery temp was still 54 degrees. A infrared heat reading showed 58 on the side of the batteries closest to the still shaded basement doors. A temp in the middle top (These are paired 2X2 next all together like a four by four square.) reflected 55.6 degrees. The Magnum temp sensor, is sandwiched half way down and between the barrettes, as close to the intersection of the four batteries as possible.) So use some wiggle room, when calculating temperatures.)
Since we're usually using the coach, and thus the battery systems, it's not always easy or practical to get a resting battery measurement. Many of the devices used to display battery health, have pretty sophisticated logic to look at Total Out/In and Temps of the battery, when calculating displayed SOC's.
Long winded way of suggesting you validate the actual SOC level:)!
Best of luck to you,
Smitty
