You don't need a 3 digit for your (and my) purpose. The only good the 3rd digit does it tell you when the 2nd digit is about to change.
And accuracy (w/ in 1/10th) is not that important, as long as it is consistent, and most all voltmeters are.
Knowing the SOC is easily learned by consistent loads. Like I know what the voltmeter reads when I get up in the morning, and I know what it reads when I go to bed at nite, having the same loads both times.
If the fridge happens to be running, that does not change the voltage enuff to change anything.
If you must check voltage at other times when heavier loads....like tv, sat DVD etc, then you must put the more loads into the voltage picture.
I know my system so well, I have no use for a "monitoring system"
