My state of charge reading has not been accurate since installing the bmv 712. I can be at 12.2v on the battery and the state of charge will read 100% or there abouts.
All wiring is correct and the parameters have been set correct via the app. Also when viewing the history is claims that is has synchronized 0 times despite me manually syncing it when at full charge.
Is the load current reading correctly?
Could you post a photo of the unit wired in?
Hiï¼Mitchorr
Most of the problems we encountered in the actual application process are the termination of the Shunt Load and BATT terminals.
Or there are other cables that have not passed through the Shunt and are directly connected to the negative battery.
As far as I can tell, your wiring is fine.
So, when you put a load on the battery, 10A for example, does this amount of current register on the BMV when you have it on the Amps display screen or app? Likewise, when charging, do you see the expected figure on the display? Then we will know that it is actually registering energy to and from the battery. If this is working correctly then it must be some setting that's been missed.
If I remember correctly, manual synchronizations don't count.
I'm experiencing the same symptom. However, I'm pretty sure where the problem is. I have an aging bank of 2 lead-acid batteries. They are being trickle-charged by a small wind turbine and 200W solar panels which amounts to basically nothing this time of year. The self-discharge of these batteries is so high that the voltage has dropped from 12.7V down to 12.2V in a month (50% soc drop). However BMV will happily report ~ 90% SOC with no amp hours drawn from the battery. The coulomb counting algorithm of the BMV does not (and cannot) take into account self-discharge which is internal to the battery.
Yeh, try adjusting the round-trip-efficiency in the BMV. And don't be afraid (or surprised) to have to go even below 70% to see a practical SoC. Pb's are notorious for this, even fresh ones.
Floodeds will bubble too, and there goes your RTE..
only the one wire going to the negative. 
