I am relearning how to think about 'range' for my boat recently converted to electric drive. I have noted that State of Charge is close to useless the way I am using it ATM. I have been told that this is because I am leaving the battery connected when the boat is idle and the small current draw of the circuits is not measured accurately (shown by the battery monitor as 16W with a 48V system => 0.333A). The battery bank has a capacity of 200Ah.
The specification sheet at https://www.victronenergy.com/upload/documents/Datasheet-BMV-700-series-EN.pdf says the current measurement accuracy of the 500A shunt is +/- 0.4% and the State of Charge accuracy is +/- 0.1%. But I have seen at least one post her suggesting that +/- 0.4% is relative to the shunt capacity, i.e. +/- 2A. That doesn't seem right because even if I'm discharging the bank at 5kW or 100A over 2 hours (0.5C), that's still only +/- 2% of the measured current and hardly what I would call 'a highly accurate monitor'
In my naive mind. 0.333A for a day is 8Ah. The question is has my battery discharged somewhere between 8.032 and 7.968 Ah or has it discharged somewhere up to 14 Ah a day which seems to match my recharge data? In other words, is there data for current measurement accuracy at different rates of current consumption? Failing that, what is the current consumption rate (e.g. 0.2C) at which 0.4% is determined?
