Which is cheaper? Recharging the battery from the grid or direct power consumption from the grid?
two days, similar load, similar weather, high versus very high grid prices.
day 1
toping of the battery in the night to 45% (0-5:00),
Minimize grid usage / maximize battery usage, No importing from grid to battery (5-22:00)
keep battery idle (22-0:00)
keep battery idle (0-3:00)
toping of the battery in the night to 20%, (3-4:00)
keep battery idle (4-6:00)
Minimize grid usage / maximize battery usage, No importing from grid to battery (6-22:00)
keep battery idle (22-0:00)
My system has a roundtrip efficiency of about 50%, which means every kWh used from battery has to be placed twice in the battery either from grid of from PV. So, for a wide range of times it is cheaper to use the grid directly than to top of the battery and use that later. I can’t find this strategy used by DESS.
Not even if you set the DESS-efficiency to 50%? (By the way: really only 50%? That’s massively low…)
I have set efficiency to 73% and DESS only plans to charge from the grid if the price ratio of charging / discharging is <= 0.73.
At least DESS then plans correctly. (Only actual charging is then partly executed at other times, DESS is still faulty in this respect, but Victron is supposedly already working on fixing the error, see parallel thread)
What I said above ist what I expect from DESS. And at times with lower prices (charge price / actual buy price > 0.73) DESS uses the grid instead of discharging the battery.
This means I can easily set the desired behavior using the DESS efficiency parameter via Node-RED, for example. So everything is fine in my opinion.
Another issue is the strategy “Follow the target SOC” which does not include internal consumers like the quattro itself. Those internal consumers draw my battery by 0.75% any hour, so the system tops the battery from grid even if the “enable charge battery from grid restrictions” are enabled.
If I want to prevent this, I could manualy lower com.victronenergy.settings /Settings/CGwacs/BatteryLife/MinimumSocLimit by 1 every hour.
So I have a KI which tops my battery from grid and consumes unnecessary energy, while preventing this is only a few lines of code. My Christmas wish:
