I set my lynx shunt to 51% last night, as this was the soc my battery bms was showing, i wanted to monitor them both to see if they keep up with each other, but today i looked and the shunt is back at 100% soc, why does it keep doing this?
The information if a bit “short” to make an assumption. But my best guess is that you selected the minimum SOC unless grid fails. This does not stop the PV or chargers from charging to 100%. Do you have scheduled charging active that might be the culprit?
I also have the Battery BMS information via CAN to Cerbo visible in the VRM. Works quite well withing 1% of delta if the Victron Shunt’s settings are made properly. In my case the 500A Smartshunt. Grid offers 60 cents per kWh today in Finland, hence the discharge to grid…
If the Battery has not been charged to 100% in weeks but has been cycled daily, then the small differences in the current calculations will drive the two shunt SOCs apart. But once both reset to 100% from time to time, then they will keep sync quite closely. Hope this helps.
@mfred868 There is a FAQ covering this issue listed in the sticky first post at the top of the DIY category.
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Good call. I might have misunderstood the issue based on such a short description. If you set the “Charged voltage” and/or the “Tail current” to a illogical value, like to 12V on a 12V battery, then it will keep resetting the SOC to 100% every couple of minutes(based on “Charged detection time” value). It needs to represent the peak value of the charge voltage curve that is close to the absolute peak that represents your battery bank’s values. On mine that value is 52V on a 48V S15 LiFePo4 system.
Yes, you have understood correct, if the charged voltage is too low the shunt syncs to 100% too easily, especially with solar where voltage starts to rise slowly with low current flow as the sun comes up, so you definitely need the charged voltage to represent peak charging voltage.
No I meant that I misunderstood the question of the original poster’s (mfred868) issue.
My answer was to provide a solution to a different (wrong) problem =)
Yours was most likely on the right track what he was asking for…
Thanks guys, you have been very helpful, ill look into this when i have the time.
Btw does the charge voltage have to be the same parameters ast the mppt’s? Which are set to the parameters stated in the battery documentation.
The shunt charged voltage is a different function to that set in the MPPT and has a slightly different purpose and value. Read the FAQ I linked, I wrote that and it is fully explained in there so I will not repeat it here.