Off-grid situation - “Victron installation: Multiplus II GX 48/5000/70-50 with 3700W solar inverters (Huawey + SMA) on AC-Out1 (AC-coupling), 4 Pylontech 48V batteries, connected 2 by 2 (19.2 kWh) + MPPT RS 450/100 with 4200 Wp solar panels. Problem: the multiplus limits solar production in AC-coupling as soon as the MPPT sends 70A of load to the battery, whereas the MPPT can go much higher (100A) and the 4 batteries accept more than 70A of load current. What setting can be made so that the multiplus doesn’t limit AC-coupling on the basis of the current sent by the MPPT?”
Just to be sure. The MPII is seeing the pylontech BMS ?
Yes
communication cable
In DESS/advanced activate the Battery monitor the widget Charge and discharge Limits.
What is this widget telling you about de “Charge Current Limit” ?
Can you go to the battery in the device list and see (under details or parameters) what Charge Current Limit the BMS is requesting when this happens?
The 35A rating of each Module is not applicable for a high SoC and due to temperature the BMS may even request less than technically possible.
I have 8 Pylontechs and their Charge Current Limit drops to about half, when the SoC reaches 80ish percent.
It does not look as the BMS limits the charge currant. The Multiplus seems to do this without taking into account the existence of the MPPT RS… Is this normal? The multiplus knows the currant it sent to the battery and also knows the currant received by the battery…
What are your settings for DVCC? (Settings → DVCC)
Inside DVCC there should also be a selection “Controlling BMS”, make sure you select the Pylontech BMS there.
Else the actual values reported by the bms won’t be taken into account.
If BMS control is active, your Multiplus should report the state “External Control” rather than anything else.
Showing States like Inverting/Conversion means your multiplus is running according to the settings done in VEConfigure, not listening to the BMS.
(Not 100% sure if this applies for offgrid situations as well)
You should set them (VeConfigure) properly for fallback purpose, but generally let the BMS take control.
Hi,
you have a 70A limit configured there. So, since you are offgrid, the multi has to either throttle ACPV or DCPV to keep that 70A limit.
Since throttling of ACPV would require frequency shifting, I believe it is most likely deciding that it is preferable to throttle the MPPT so the 70A Limit is obeyed.
Issue is that the multiplus is taking to charge currant of the battery as the limit of 70A as maximum set-point for its control of ACPV, when Multiplus should take its own measurement of what he sends to battery as set-point. With the RS the charge currant is 70A from MP + 100A from RS, which is 170A. Something is fishy in the two max. setpoint of the MP (which should be 70A max from MP to battery for ACPV and 100 A max from RS to battery for RS control).
The Limit in DVCC is a general limit.
You are limiting Multiplus + RS to maximum 70A battery charge combined.
And then, the RS will be curtailed first to not exceed that limit.
You probably want 170A to be set in DVCC. But you only need to apply a limit at all, when you want to keep the current bellow what the BMS requests.
The limit in DVCC is greyed, not changeable…
Hmm, your screenshot looks like it can be modified. You can also simply disable the blue slider named “Courant de charge maximal”, then there is no limit overriding what the BMS accepts.
But here you ofc. Have to be sure that your wiring is suitable sized to take the full current the multiplus and rs can provide.