Another trouble shunt

[pwfarnell]

This sounds like the shunt is not wired up correctly. On boats and RVs the normal problem with alternator charging is the engine / hull / chassis ground is connected incorrectly. It needs to go to the system side of the shunt not the battery negative. See the image below from the DIY FAQ.

Shunt / battery monitor not reading the correct SOC/ Amps, missing solar, decreasing daily or other misreading problems

This topic covers the SOC / Amps reported by BMV battery monitors, SmartShunts, Lynx BMSs and Lynx Shunts and will just be called shunt below. It is also assumed that the shunt is monitoring the domestic / house / cabin battery bank and not engine start / bow thruster / winch / caravan mover battery banks. The problems may be one or more of the following The SOC decreases daily despite the solar charger or other charger(s) working. The SOC increasing when discharging and falling when charging…