On 30 April I upgraded to v3.60~66 ( coming from v3.60~59), no other changes. 3 evenings in a row the battery was discharged to 0% while DESS is configured with min SOC is set to 5%. Going to 0% SOC generates alarms of course. Why is the SOC going under the configure 5% level?
DVCC is enabled, the system is external controlled by the JK BMS. The Multi RS Solar is configures to Shutdown on SOC level 4%, doesn’t seem to happen, see screenshot.
The SOC “steps” are 5% in victron’s code (dvcc and batterylife scripts for reference)
0 - 5 - 10 - 15 - … and so on.
Anything in between could lead to what you’ve experienced.
Also jumps are sudden, as you don’t have the elegance of jumping between consecutive values, but “brutal” 5%…
Also, no offense, but who would want to discharge a battery bone dry?.. Not good for battery health.
The MB31 cells have an End of Discharge Voltage of 2.5V for 16 cells, this is battery voltage 40v. This is the lowest volatage the cells/battery can handle. SOC 0% is at 48.23%, per cell 3.014V. This is still way above the End of Discharge Voltage. My conlusion (I could be wrong) discharing to SOC 5% is not damaging the cells.
My expectation is that with DESS min 5% voltage the battery is not discharged under 5%. Maybe it drops to 4% and than going back to 5%, but definitely not going doing to 0%. I don’t understand why this happens. Why would the steps be in 5%?
This morning again, the battery was discharged below the minimum 5%.
I’ve changed the minimum leven to 10% and will monitor what is going to happen. Will post an update soon.
The discharging of the battery just finished and stopped at the configured 10% min SOC value. This is working fine. Why is it not working fine when configured at 5%? @mpvader and/or @dognose any ideas or suggestion on how to resolve this? To get it working for 5% without discharging to 0%.
Just curious, how did you set the valuses in DESS, I found if you change the charging and discharging values, DESS will adept to that by using the bank heavily or minimal (screen of my setting)
You relate it to the update, I cannot see this behavior is the cause of venus os (did you test it by downgrading?)
Do you happen to have peakshaving switched on? If that is the case there is a option to always do peak shaving or just when above minsoc (if I remember correctly) - Always will draw down the battery below min soc and after minsoc -5% it will recharge back up to minsoc from grid when the load triggering peakshaving is gone.
/Kaj
