question

higherwire avatar image
higherwire asked

Prioritize PV with grid backup

I’m installing a system into a detached shop with a sub-panel fed from the main home. I want to prioritize PV and battery over grid input, and cannot have grid feed-in. Grid will be used only when batteries fall below a certain voltage or loads exceed a certain point. I also want to be able to charge the batteries from grid if necessary.

What is the best way to accomplish this?

Equipment:

*2x Quattro 10k setup for 240v split phase

*2x MPPT RS 450/200

*Cerbo GX with Touch 50

*48v 900Ah LiFePO4 battery bank with no SOC/BMS communication

MultiPlus Quattro Inverter Chargeress settings
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matt1309 avatar image
matt1309 answered ·

You can either use ESS (Energy Storage system) Assistant within VeConfigure and disabled "feed in excess". However I've heard this can be difficult to force absolutely zero exporting if that's a criteria that 100% cannot be allowed. ESS is more common for trouble shooting on here if you can get away with small and infrequent export amounts as system balances loads.


However if you don't want to export any/cant. I think you maybe able to use Ignore AC input in virtual switch in VeConfigure. I'm not familiar with that option though so can't really share much but if you search "victron virtual switch ignore ac" you should find the PDF explaining in further detail.


PS. Just in case you didn't know (as it's not listed in your parts list) you may need a victron smart shunt or equivalent device to allow victron system to monitor SoC of battery given you'd got no communication between BMS and victron system. (I have same setup of no BMS coms and use smart shunt for my battery monitoring)



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higherwire avatar image higherwire commented ·
Thanks, I've looked at ESS but heard about the weird grid feed-in anomolies (L1 and/or 2 negative). It won't be a problem per se, and I understand one can set the grid setpoint to 200-300w for larger systems. Will try that.

To clarify, I have Daly BMS that can communicate with Victron using CAN. However, SOC is wildly inaccurate based on previous installations so I've basically assumed that it is a 'dumb' system. Will look at adding a smart shunt.

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matt1309 avatar image matt1309 higherwire commented ·

ESS is probably easier/more common but there are definitely ways around it with Ignore AC if absolutely 0 feed in is required.


I agree dumb ftw.

Personally I prefer the "dumb" system. In my eyes I like the BMS to be purely a last resort safety device (I use JK personally). I don't like setting up BMS coms because then solar charging criteria is defined by BMS. Feels like everything relies on BMS.

Whereas dumb system I feel like I can set slightly conservative limits in Victron settings and BMS is just a last resort safety device if something goes wrong. Feels like two safety devices rather than one. I'm sure others will say you can push batteries further/more flawless system with coms but for me (with LiFePO4 cells) I'm just more comfortable with smart shunt for SoC/battery monitoring and not using BMS coms.

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