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Question How do I programatically turn OFF "Grid Sell Back" for all times but Forced Discharge period

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(@dougl)
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I'm on NEM 3 and don't want to sell anything back to the grid except for the On-Peak period of 4p-9p daily. I can't reduce the "Grid Sell Back Power(kW)" value because that also limits what Forced Discharge can discharge.

 

There doesn't seem to be an option of not selling back once my batteries are fully charged AND export some of my battery power during On-Peak hours so that I can not only help the grid during peak loads but also try to offset the additional fees IOUs are adding to solar PV customers.

If there is no way to do this in the current firmware, is there a way to connect a computer to the EG4 18KPV and send it commands to turn off Grid Sell Back and then turn it back on only for the TOU On-Peak period then back off again?

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Eric
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 Eric
(@eric)
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You can manually set the Grid Sell Back using the app or the monitoring website at 4 PM and disable it at 9 PM. However, there is currently no option to schedule grid sell back for specific times.

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(@dougl)
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@eric Thanks, I've come to that conclusion too and in the meantime I also learned that NEM3 sell-back rates are lowest during highest grid loading(4-9p) and that maximum sell-back rate for solar generators/storage is during super-off-peak times(midnight-6a).

I don't want to bother selling back at only 5 cent/kWh  so I'm now looking at Python Protocol Gateway and Home Assistant or even just a bash script to send MQTT messages to manipulate the max Grid Sell Back value based on our EV SoCs and battery SoC after sunset.

Seems a shame to have to pull the WiFi connectivity to get that to work( INV-RS485 ) but unless there is a true network Ethernet port somewhere it seems I'll have to lose EG4 Monitoring capabilities just to get some NEM 3 type system control.

BTW, I tried to get down to see you guys at InterSolar but could not find trolley parking at 3 different trolley stops.

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(@dougl)
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@eric is there a ModBus input-address associated with the "Grid Sell Back Power" setting?

 

It really sucks that the Grid Sell Back Power setting limits the other settings like Forced Discharge Power(kW).  Exmple, if I set Grid Sell Back Power to 0.5 kW so that at max it would sell back 500w after my batteries are fully charged, it becomes the max for the Forced Discharge Power when I go and dump some excess battery power late at night when we get the most $$ for our power. ie even though I have Forced Discharge Power set to 3.5kW, it will only export at 0.5kW because that's what Grid Sell Back Power is set to.

 

Manually changing this every day is a pain. And I have to keep Grid Sell Back Power above 0 because otherwise the AC Coupling of the GEN port is disabled and micro-inverters get turned off. Today, I daily change Grid Sell Back Power to 0.1kW in the morning and then in the evening change it to 4.1kW so that extra battery capacity can be sold back to help offset the monthly flat fees the utility is adding to solar customers. Knowing what the modBus input address is will help since it will allow me to programatically change this and it will let me programatically change the time ranges for Forced Discharge Power because the rate schedule is different hour by hour, week by week and month by month.

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Topic starter
(@dougl)
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SOLUTION:

@eric, never mind I believe I found it as ModBus address 103, MaxBackFlow set as a percentage of something. Im not sure what the percentage is since a setting of 10 kW in the app for Grid Sell Back results in MaxBackFlow setting to 100. Not a problem since I don't expect to output more than 4kW at any given time.

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Eric
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 Eric
(@eric)
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I'm glad you were able to get it to work! Let me know if you run into other issues. 

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(@dougl)
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@eric I noticed on our recent bill there were a few kWh of grid consumption power and I believe it's from little blips of grid power usage I see on the data page. Can those be eliminated by setting Off-Grid Mode enable while still allowing Force Discharge feature to function? 

The goal is to use zero grid power but still export excess battery at peak export pricing times.

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Eric
 Eric
(@eric)
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@dougl This is not possible. Enabling Off-Grid mode completely stops both importing from and exporting to the grid.

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(@dougl)
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@eric So it sounds like Off-Grid mode = Enable will stop any and all export and import. It turns out this is a good thing since not only did we see a few kWh of energy being pulled from the grid( in short spikes ) but we also see every hour of the day there's -0.07 kWh exported and it turns out for every hour we export anything, that hour's export rate is added to the daily accumulated mean price value. So we do not want any exporting unless it's directly associated with the Forced Discharge operation.

Crazy as it is, our recent bill from the utility had them paying us for exported energy at a rate I could not figure out. After talking on the phone I was told they take the median of the exported rates and come up and use that median rate to base the export credit on. Because we were exporting very small amounts throughout all hours of the day, they took all the daily hourly rates to produce the median.

I now have to find a way to disable Off-Grid mode when the Forced Discharge time range is triggered then enable it again once the Forced Discharge timer expires OR the low SOC is reached. ie when the Forced Discharge operation terminates.

Thankfully when I enable Off-Grid mode the AC coupling system stays active. This is not the case when 0 is set for the Grid Sell-back value.

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(@dougl)
Joined: 4 months ago

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@eric can someone at EG4 tell me what's getting set on the inverter when the web page Off-Grid Mode is enabled and disabled?

I'm monitoring FuncEn_ESPEn but do not see it change when Off-Grid Mode is toggled. I've also tried looking at FunctionEn1_ubPVGridOffEn and also no change.

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Topic starter
(@dougl)
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Joined: 4 months ago

Posted by: @dougl

FuncEn_ESPEn

oops, I'm monitoring FuncEn_EPSEn and it's remains set to 1 no matter if Off-Grid mode is enabled or disabled.

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