When I first switch on* my Cerbo GX/Multiplus II (which is configured for ESS), the first thing it does is charge the battery. Presumably it does this so that it can estimate its state of charge.
How long should it be before it switches to inverter?
The battery was fully charged when it was switched on, and so far it has been in Absorption for 2 hours.
Is this in the Charger settings in VE Config? Does it have to get to float?
*No, I didn't switch in on in "Charger only" mode.
Well, you did not list your settings.
For instance did you set "Keep the battery charged" in Cerbo?
There are a lot of settings! I suppose that the one you most need to know about is the one where I set "Optimised with battery life",
Others are: Grid Metering - Inverter/Charger
Minimum SOC 50%
BatteryLIfe State: Self-Consumption
Limit Charge Power: ON 4000W
Limit Inverter Power: ON 4000W
Grid Setpoint: 20W
Grid Feed in: Off
What are the ESS settings (those programmed in the inverter)?
Which device is set as "battery monitoring" device in Cerbo?
What battery?
Any BMS?
Is the BMS communicatting with Cerbo?
etc.
PzS battery, 695Ah.
The Multiplus II is set as the battery monitor.
Do the Multiplus II charger settings make a difference? They were the standard PzS battery settings, with automatic equalisation disabled.
What is the current battery voltage?
Is this an old(er) system which used to work properly or is this a newly installed system, used for the first time?
It's new. I got the MultiPlus a few months ago, then got the Cerbo GS last week. The battery voltage is 50.4V open circuit.
I checked the settings in the Multiplus with the computer and the interface and changed the "current sensor" from external to internal to see what would happen.
Now it works, except for one thing - when it is inverting the LEDs indicate "bulk charge" and "inverter" flashes.
When I got the Multiplus, the manual that was supplied was for a Multiplus with a 3.5mm jack for the external current sensor, but the connector fitted was a 3-pin terminal block.
I also think that the Multiplus was made with metalwork intended for a 3.5mm jack as the external jack connections are unlabelled, and later manuals show "INT""EXT" and "Common".
It didn't help that the 3-pin plug-in terminal block had fallen apart and I had to mackle it back together, replacing a terminal that had gone missing by the one that wasn't used.
The battery voltage is 50.4V open circuit.
That does not sound like a fully charged battery.
Your ESS system could be in "Sustain Mode" and that's why it is charged from grid.
Manufacturer’s datasheet - an odd way of presenting the data, but it is about 80% charged.
Especially Dynamic Cut-off voltages, Sustain voltage.
I note that the same thing happens in this explanatory video:https://www.youtube.com/watch?v=xHQGOfSGQd4
it is clearly doing grid tied inverting, but the LEDs are indicating bulk charge with the inverter LED flashing.
If you disconnect the grid, does the Multiplus switch into inverter mode (powering the critical loads)?
Yes.
(Apparently, the answer "Yes" is too short)
Could you please clarify “grid set point” -the point at which power is taken from the grid in self-consumption mode. I would expect that to mean about 4000W I.e. below 4000W it takes power from the battery, above that it takes power from the grid. I set it to 50W as it says in the manual, but the rationale is puzzling me.
Another thing:
What is the SOC as dispalyed on Cerbo/VRM?
You wrote that your Minimum SOC is set at 50% and you are using "Optimized with BatteryLife".
What's your Active Minimum SOC right now?
If the SOC is 5 procentual points lower than the Active Minimum SOC, the inverter will charge the battery from the grid.
It was saying SOC=100%
You did not mention if you have other ways to charge the battery (besides the Multiplus)?
MPPT?
PV inverter?
It will be charged from solar panels, but I am trying to commission the MultiPlus before I introduce any extra complexity.
I initially assumed you have a typical system, with an MPPT, since you did not mention you only have the Multiplus.
Not sure how the ESS "Optimized" modes are supposed to behave when you do not have any MPPT (nor a PV Inverter) and the Multiplus charger is the only available battery charger.
Basically, without any kind of solar, there is no point to even use ESS.
As I said, solar panels will charge the battery. If I can’t persuade the MultiPlus to discharge the battery, then the solar panels are superfluous!
I don’t need many of the features of ESS, all I need is a grid connected inverter which is controlled so that it doesn’t export, a feature which is only available (as far as I am aware) via the Cerbo and the ESS settings.
