October 6, 20232 yr I have 2x Rebel Max Inverters (just voltronic rebrands). I am currently running on beta software on Solar assistant (27-09-2023). But this issue has been like this for the past 2 versions or so I feel. So what happens is - if I am up late at night and I know its going to be quite a sunny ay the next day, I switch the inverters to SBU to run the household off the batteries to run them down to about 50% or so - because we produce power in excess, if we dont do this - we are essentially dumping power. I changed the output source priorty to SBU (from USB). This does what I expect, starts drawing power from the batteries instead - all is well. Then the weirdness kicks in - for some reason or another - the inverters start drawing from the grid again (despite me not changing it back to USB), this isnt because the batteries have fallen below their SOC settings (or at least I dont think so - continue reading on). You can see it suddenly start drawing power from the grid again in the screenshot below - at about +- 05:50: You can see shen I switched to SBU to run off of battery power as there is no Red Grid Power line. and then just suddenly a spike. Now when this happens - SolarAssistant home page that shows you which state your inverter is in shows: Grid Tied (SBU). Now I have seen this before - because the (SBU) in brackets, I interpret it as showing a "pending" state, because when its in full SBU mode it doesnt show "Grid Tied" but "SBU tied" as its status. But when you go into the power management tab, it says the inverter is in SBU state (despite the whole system not functioning that way): And to round off all of this absolute weirdness - if restart your RASPI while all of this weirdness is going on... when the RASPI comes back - it REFUSES to connect back to the inverts (I have mine connected via USB (Micro USB in the inverter, USB A to the RASPI). The only way to get the RASPI to connect back to the inverters is to do a hard reset of the Inverters and let everything boot up again. This eventually goes away on its own - but its incredibly annoying because it does come back again.
October 6, 20232 yr Author I just had a thoguht and went to go look at what ouput mode was reflecting on the inverters themselves. They showed SBU. As I started to walk away I heard the relay click over and I immediately thought "thats odd?" I check on Solar Assistant - the correct Output mode now shows: It almost seems that me just flicking through the inverter settings, (not changing anything just going into the menu interface) and then exiting the menu interface which seems to have "commited" the SBU settings. Its very strange.
October 6, 20232 yr Check again your Back to Discharge Voltage setting, either in the inverter or in Solar Assistant. I am hunting an issue you can read about in here:
October 6, 20232 yr Author 20 minutes ago, onobeka said: Check again your Back to Discharge Voltage setting, either in the inverter or in Solar Assistant. I am hunting an issue you can read about in here: Very interesting. Took a look at my settings:
October 6, 20232 yr Author 33 minutes ago, onobeka said: 0V? Seems my issue might be related to the "To Grid" Battery Voltage being set to 54 which seems quite high to me. The voltages in my screenshot is what was configured by the solar installers. When I look at battery voltage at the time my inverter switched over to grid: You cna see at about the same time - Battery voltage had reached 54v before kicking back over to grid. So I have dropped that down to 52v to see. I have Lithium NMC batteries so using a SOC to voltage table is quite hard for a 48v NMC as a lot of the guides are for LIPO batteries. So HOPEFULLY - if my guesstimations are right 52v should hopefully be around 40% SOC. We shall see.
October 6, 20232 yr 25 minutes ago, ABarelyFunctionalHumn said: I have Lithium NMC batteries Here is the cell voltage vs SOC curve for NMC cells. Don't you have a battery to SA connection to actually see the cell voltages? https://www.mdpi.com/2313-0105/4/1/11/htm Edited October 6, 20232 yr by zsde
October 6, 20232 yr Author 37 minutes ago, zsde said: Here is the cell voltage vs SOC curve for NMC cells. Don't you have a battery to SA connection to actually see the cell voltages? https://www.mdpi.com/2313-0105/4/1/11/htm I dont no sadly. I have Arco Invincible III's NMC batteries - so BMS is communicating with Inverter so SA is just reading off inverter. Not the most accurate - but its all I got 😕
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