Cool looking and accurate for SOC are two entirely different things. If you don't mind fiddling with an Ah counter, testing for actual Ah capacity, etc., etc. then the SimMarine can give you a lot of good info but currently it does not track SOC as well as it should.
If you want super easy, the original Balmar Smartgauge is about as simple and accurate as it gets but it will not work with LiFePO4.
The new Balmar SG200 expands on the accuracy of the Smartgauge and adds a shunt and a state of health feature. The new SG200 also works with LiFePO4 and is self-learning meaning no continual fiddling to keep the monitor in sync with your bank as it ages and gets PSOC cycled.. The longer it remains connected the more accurate it gets. The way the self-learning SG200 works is the complete opposite of the rest of the Ah counters currently on the market.
Also keep in mind that you really only need to know your SOC perhaps once per day so the display does not even need to be prominent, and can even be mounted inside a cabinet etc.. The original Smartgauge is very antiquated looking but also very accurate. The SG200 is better looking, expandable, less money and also very accurate.
Have you got experience with the Simarine system? From what I have read so far it is supposed to "learn" the battery bank just like the others do, but I have yet to find any testing or reviews that evaluate how well it does that.
While it it nice to have a good looking, modern display, there are a lot of other things going for the Simarine product. For starters, it is expandable. You can add shunt modules that allow you to monitor amp draw and track power consumption on individual loads. You can add tank a tank module to monitor status of water, fuel and black water tanks. You can monitor current input from each charging source. There shunts also have temperature sensor inputs, so you can monitor battery temps, or repurpose the temp inputs for things like inside and outside air temps, and refrigerator/ freezer temperatures. All that data can be presented on screen in whatever format you choose.
The system broadcasts it's own wifi signal to allow you to interface with your mobile device, which also allows quick and easy software updates. Presumably that means that the manufacturer can continue to improve their algorithms and add functionality in future. (That is no guarantee that they WILL of course, but they CAN!)
Of course all of that functionality comes at a premium price, but for many it may be a worthwhile investment.
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