Originally Posted by Orv
I have a Victron. The percent capacity measurement actually works pretty well, but it is dependent on you accurately telling it your battery's capacity;
I have owned a Xantrex, and am currently running a Bogart Engineering Pentametric , they also make the Trimetric such as the TM-2030-RV. I also have a Magnum Inverter so I have the Magnum BMK installed. I also would not hesitate to use one of the Victron units, or just about anything Victron makes.
All of these are good units, but they all use the same principle to calculate SOC. Because as your battery ages your capacity decreases, it is hard at times to keep up with an coulomb counter battery monitor. Imagine you put 210 amp-hrs in for the capacity of your new 4D battery. You diligently watch your usage and never let it drop below 50%. Now fast forward 2 years, do you think the capacity of the battery is still 210 amp -hrs (if it really was in the beginning).
Let's say it's 200 amp-hr capacity now , the 105 amp number that would give you 50% SOC is now really giving you 47.5% SOC. All the while you think your doing a good job managing your battery, you could actually be speeding up the degradation.
The Smart-Gauge battery changed that, it doesn't count amps to develop its SOC calculations. The how it works is proprietary and beyond my math skills, but is has proven to be vary accurate across multiple battery chemistries. The Balmar SG200 takes the original Smart-Gauge and adds a shunt to do the amp counting. This allows you to monitor the current devices use and the charge that is being put into your batteries. It does not display amp-hrs although you could roughly calculate using time remaining.
The feature other monitors don't have is a state of health calculation. Because that have now added the shunt they can calculate how many amps were put back into the battery during the charging process. They can now measure that do the expected capacity and give you a health indicator.