with your conclusion. I just don't think SOC is a very useful number. I have two Coulomb counters in my system, one by Mastervolt, one by Blue Sky. Yes you do have to install them correctly, and set them up correctly. They are quite accurate and will read within a couple of AH of each other over many days (as you know they 'reset' when they think they had a full charge), and based on other data (observed voltages and recharge rates) accurately represent the energy state of the battery. What I want to know is how many amp hours have I used and am I using, and how many have I replaced?

I believe that SOC is meaningless unless a bunch of other factors are known - like AH capacity, current load, recharge capacity etc - none of which the Balmar meter shows. In fact the only thing that SOC is even useful for (directly) is to judge how deep to discharge your batteries, with the often written goal of "less than 50%". But this is itself a very soft number: your batteries do not instantly fail if you go to 40% SOC, nor do they last forever if you only go to 60%, nor is it practical in most cases to pick an exact SOC point to begin charging (with the exception perhaps of power boats with automatic start genets). If your batteries do not have the capacity programed correctly, the SOC error is not dramatic: 100 hours out of a 220 AH battery is 55% SOC, out of a 180 AH battery is 45%. Nevertheless it is still 100 AH that has to be replaced by some means, for a sailboat cruiser this is what is important.

If you are saying that the Balmar meter is an appropriate device for someone without much knowledge about batteries or charge systems, or for systems improperly installed or configured or maintained, then I agree. It is a "dumbed down" instrument which would be useful in those situations. Otherwise I think it quite inferior to a good AH counter. Having both I suppose would be best, but I can think of no reason whatever for me to add one, even if it was given to me. I should disclose that, being an EE by training, perhaps I am more comfortable with these systems than some might be.