In a system with Multiplus, Cerbo, battery, solar on the Multiplus-output and a PV-charger I want to use ESS, but, I want only the PV-charger (MPPT 150/35) to be controlled by Node-Red in the Cerbo.
If I switch ESS on, both Multiplus and PV-charger start simultaneous charging the battery.
The ESS feature in Cerbo works fine, but I would like charging the battery with de PV-charger with a different pace.
It seems like the PV charger (connected with VE.Direct) is always under control of ESS.
I like to keep the VE.Direct connection to have all the parameters available in VRM and Node-RED.
Can you explain a bit more, what you want to achieve?
Best would be to provide a example with “Power-Values” and your expected energy-flow in that situation.
ESS will charge the batteries with all surplus PV, that is how it’s designed to work.
You can’t differentiate between DC and AC charge rates, you can only limit the total battery charge rate.
It might be worth running through the ESS training and manuals.
Thank you for the answer. I found in the documentation of PV charger:
Generally speaking, the MPPT Solar Charger will be more effective than a grid-tie inverter in a small system. This is because an MPPT Solar Charger is up to 99% efficient, whereas the PV energy coming from a grid-tie inverter is first converted from DC to AC, then back from AC to DC, causing losses up to 20 or 30%. This will be even more noticeable when the energy consumption occurs mainly in the mornings and the evenings.
My aim is following:
When it is expected the DC charging will be more efficient to fully charge the battery at the end of the day, I prefer to charge with only DC components. The Multiplus units could in that case better not convert AC-IN power to DC power but have the AC power on AC-IN (SolarEdge) flow directly to the grid to sell.
I tuned down the max battery charging DC current to 15A. It seems like the Multiplus units tune down and the PV charger keeps charging with +500W, what feels like not tuned down. (Only two PV pannels).
Thank you for this comment. That gives some confidence, it works as intended.
With Node-Red I might tune the max charging current? That feels not very good as this setting could potentially put the battery in a destructive charging rate. (I want to avoid software to be able to put hardware into a (very) destructive situation.)
It seems there is some priority here.
ESS does not tune down a DC-PV-charger but it tunes down the Multiplus.
I could not find the behavior in the documentation. (Always feels I miss some docs.)
Can that priority be influenced?
That’s not some sort of priority thing. DCPV is literally directly connected to the DC-Bus as the battery is. So, whenever the multi is idling or sending a single watt to the DC Bus, the battery has to take 100% of DC-Solar as it has no where else to go.
No, it won’t. If you have the charge-voltage configured correctly (Or use BMS-Control) the energy flow will simply approach “0” when the chargevoltage of the MPPTs and battery voltage level out, when the battery approaches 100% SoC.
The charge voltage is not of concern. It is more the maximum current allowed to charge. If software puts (in a unhappy scenario) 3x Multiplus to charge at maximum capacity I need to verify if the battery can take this stress situation.
If ESS tunes down the Multiplus units to charge indeed. It appears however, ESS is also capable of tuning down the DCPV charger as the battery reaches 100% SOC. That feels like some sort of priority. I do not understand what exactly DC-Bus means. Is that the just the hardwired 48V system or does it mean some software logic inside Cerbo’s activities?
