question

Hi @cossie1600, welcome to the Community!

As noted in the SmartShunt user manual:

"5.1 How does the SmartShunt work?

The main function of the SmartShunt is to follow and indicate the state of charge of a battery, to be able to know how much charge the battery contains and to prevent an unexpected total discharge. The SmartShunt continuously measures the current flow in and out of the battery. Integration of this current over time, if it was a fixed current, boils down to multiplying current and time and gives the net amount of Ah added or removed. For example: a discharge current of 10A for 2 hours will take 10 x 2 = 20Ah from the battery. To complicate matters, the effective capacity of a battery depends on the rate of discharge, the Peukert efficiency, and, to a lesser extent, the temperature. And to make things even more complicated: when charging a battery more energy (Ah) has to be ‘pumped’ into the battery than can be retrieved during the next discharge. In other words: the charge efficiency is less than 100%. The SmartShunt takes all these factors in consideration when calculating the state of charge."

So you can see that the SmartShunt is not using battery voltage at all for its SOC calculations; the manufacturer of your batteries may list rough equivalent battery voltages for approximate SOC, but the reality is that actual battery SOC is far more complicated than that and the SmartShunt is performing real calculations based on your usage (assuming that it's correctly programmed) rather than just wildly guessing based on voltage alone.

As for BT range, obviously the range of BT in any device depends on a multitude of factors with the most obvious one being installation location; the BMV-712 doesn't inherently have better range, it's just that the BT module is located in the display rather than on the shunt, and so since the display is more likely to be mounted in a living space away from wiring and steel battery boxes and etc, it's far less likely to encounter significant sources of interference.