question

Hi from the USA, @SMT. If >>all<< energy to & from the battery moves through the Victron inverter/charger...its SOC calculation would be much the same as if you had a shunt & BMV type amp hour monitor.

Many installations, however, have energy reaching the battery or departing the battery which cannot be known by the multi--specifically if solar arrays are DC coupled to the battery by way of an MPPT charge controller or PWM charge controller...because that energy does not travel through the multi on its way to the battery. OR: if there's a Phoenix battery charger or engine alternator driven recharge for the coach battery, etc. those also cannot be known by the multi. OR: if there are DC lights or DC appliances...that is energy departing from the battery without the multi having a clue.

I'm including a shunt & BMV even on some "all AC" projects (in which even the solar energy moves through the multi, AC coupled). The additional reason to include the shunt & BMV is if the client ever wants to measure the amp hours capacity of the battery bank to see how it's holding up, using the menu function called "Consumed Amp Hours". It's a handy yardstick to have in place.

Sunny Days!