How to Read Lithium Boat Battery State of Charge

How to Read Lithium Boat Battery State of Charge: steps

Stop reading voltage as a fuel gauge
A LiFePO4 bank sits near 13.2 to 13.3 V across most of its usable range at 12 V nominal. The difference between 70% and 30% can be a tenth of a volt, which is less than the error your wiring introduces.
Read the shunt's amp-hour count
The monitor counts every amp-hour that leaves and returns. That count, against the capacity you entered, is the only reliable state of charge on this chemistry.
Check it is synchronising at full
The monitor re-anchors at 100% when voltage and tail current both hit their thresholds. A monitor that never reaches 100% is usually reporting a charging problem rather than a monitor problem.
Re-synchronise every few weeks
Amp-hour counting accumulates small errors from efficiency and measurement. A complete charge periodically resets the reference.
Use voltage only at the extremes
Voltage is genuinely informative near the very top and very bottom of the range, where the curve finally steepens. In between it tells you almost nothing.
Watch consumption, not just percentage
The instantaneous amps figure is the most useful number on the monitor day to day. It shows what a load actually costs and finds the ones you forgot about.

Judging the bank by resting voltage.

The curve is flat. Use the shunt's amp-hour count.