I have an all-Victron equipment + LiFePO4 Amperetime batteries system that has been operating since last fall ('22). I did not have a shunt until about a week ago, using the inverter's estimate to gauge battery depth of discharge. It was way off. I actually bought an additional (third) $700 battery because I thought I needed it to power my AC. After installing a Victron Smart Shunt at the same time I installed the new battery, I now see that the additional battery was unnecessary. I wish I had installed that shunt on day one, even though I like having the additional spare capacity. Winter's coming and all that.