open disclosure DESS (Green mode) settings checklist
- requires @dognose DESS HACK
- all numbers are examples and have to be adapted to your system
- this document ist best effort and subject to change, comments welcome
calculate system efficiency
example:
from victron VRM installation overview page: Downloads: production report
Battery: discharge kWh / charge kWh = roundtrip efficiency
roundtrip efficiency: 0.591
sqrt(0.591) =>
system efficiency: 0.769 => /Settings/DynamicEss/SystemEfficiency 76.9
1/0.769 =>
energy needed for 1kWh in the battery: 1.3kWh
=>
dognose HACK: dynamicess.py: line 528: chargerate = round(1.3 * (percentage * self.capacity * 36000) / abs((end - now).total_seconds()))
reinstall modified dognose HACK dynamicess.py at this point and reboot CerboGX.
calculate your personal best price
example:
costs: PV → battery → house/grid
16.8/0.769/0.769=28.409
so it is cheaper to use grid if price is below 28.409
DESS calculations are based on sell price,
so we have to calculate backwards (keeping effiency in mind):
28.409/1.3=21.853
calculated sell price setting:
Sell price type: fixed
Sell price: 21.853
battery settings
example:
Take a look at VRM: advanced: Gateway: System Battery Power widget
and estimate your systems sustained battery charge power.
sustained battery charge power: 3.3kW
use this number for your DESS Maximum charge power setting and let battery price be NULL until everything is working as expected:
Maximum charge power: 3.3kW
battery price: 0
Modify your battery usage scenario: (for example via dbus-spy on cerbogx)
/Settings/CGwacs/BatteryLife/MinimumSocLimit 0 (use 100% of available battery)
/Settings/DynamicEss/MaxTargetSocForIdle 66 (if calculated, use grid up to this SOC for consumption and keep battery idle) (2/3 of available capacity) (defaults to 100% and is used for Adhoc charge also)
Summary
This all leads to the following system state:
DESS green mode with @dognose DESS HACK improvements
DESS should use 100% battery capacity (MinimumSocLimit 0)
DESS should use grid if price is below 21.853 and SOC is below or equal 66% (MaxTargetSocForIdle 66)
DESS use a maximum charge rate of 3.3kW per hour for forcasted SOC calculation
DESS calculations are made for a specific average per system effiency rate