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I have a Smart Shunt 500. I have 2 x 130Ah 12V lead acid leisure batteries connected in parallel. At night when the solar panels are shut down and with the inverter off the smart shunt shows a battery voltage of 12.21V, and a SOC of 98.1%. I have looked up several on line battery voltage verses SOC tables, and they all indicated the battery SOC should be around 65%.
Can anyone explain why the Smart Shunt seems to over estimate the SOC?
Either there is something up in the wiring or something in settings.
Please share those. Can help you if we can't see what you see.
If anything it's the peukerts.or capacity is incorrect.
Do you experience jumps in SOC in your “trends” tap in the app?
If you see jumps from lets say 85% to 100% Soc the shunt is not set up right, and detacts a full charge too early
What is the current reading when there is no charge and discharge source?
As in everything disconnected after the shunt?
Wondering if a zero current calibration was done when there was a load on so it is ignoring the load.
Unfortunately I don't have a circuit diagram, its the same as the diagram below with 2 batteries in parallel
All the cables are 25mm CSA and the battery cables are the same length
A couple of thoughts on the settings.
You have 2 x 130ah batteries so the capacity is 260Ah since you are running a 12v system
Charge efficiency factor I can only comment on when I know exactly the chemistry in your battery. Lead acid is pretty broad.
What firmware is the shunt running?
Also increase charged voltage. This should be just below absorption for solar charging, just below float for AC chargers.
From your voltage observations, the batteries are not getting a sufficient charge. You might need to consider an increase in charger size or charger settings.
In addition to what @Alexandra asked, it would help a lot to know what charging you have, what the charger settings are and what's recommended by the battery supplier.
You have 2 batteries. So at C20 your capacity is 200Ah (2x100Ah) then your screen shot shows 100AH.
Capacity over 20 hours your load is expected to be about 10A to see that capacity.
And I do also agree with @kevgermany observation on charge sources and synchronisation.
The batteries details are as follows
Deep Cycle
Hgh Performance Calcium Technology
Wet Acid
(L)353mm x (W)175mm x (H)190mm
C5 - 80ah
C20 - 100ah
C100 - 130ah
I followed the instructions in the installation guide and input the C20; value for the batteries
4.3.1. Set the battery capacity value
In the VictronConnect app, see: Settings > Battery.
The battery monitor is by default set to 200Ah. Change this value to match your battery capacity. For lead-acid batteries, we
recommend entering the 20-hour (C20) rate.
LA batteries need to rest for 12 hours or so after being fully charged to dissipate the surface charge. This includes automotive type batteries. During that time the voltage will drop somewhat then become much more stable. A DC volt meter helps. It's at that stable voltage where you set the SOC at 100%. For my own SLA batteries I waited 24 hours before setting the SOC.
If that doesn't help then as Alexandra says there may be something else to look for.
Do you have flooded lead acid or agm nor gel?
Personally I consider 12v on lead acid as discharged. But there are varying opinions on it
There is quite a science to charging batteries a bit is explained in energy unlimited.
