Mau921020 Posted July 3 Share Posted July 3 (edited) Hi, I have a an RCT-AXVM3-5K 48V inverter connected to 2 pylontech US3000C batteries. The inverter is set to only charge using solar power. But for some stupid reason it's still using grid to charge. I only noticed because my power bill went up. The inverter is also set to SUB but have now changed it to SBU with back to grid voltage set to 48V. Why would the inverter all of a sudden just start using grid power to charge even though it should not. I am running solar assistance via USB on a raspberry pi to monitor the inverter. I have recently updated the Solar Assistant to the latest version. I cannot recall that it did this on the previous version. Could this be a Solar Assistant issue or is there something going on with my inverter? Please help. The inverter is now pulling extra power for absolutely no reason and it's using the same amount of power in a month as my geyser. Also, I have 7kw/h of storage, but solar assistant says I only have 4.8kw/h. Edited July 3 by Mau921020 Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 4 Share Posted July 4 It could be a firmware issue. What is your present main (U1) firmware version? Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted July 4 Share Posted July 4 13 hours ago, Mau921020 said: Hi, I have a an RCT-AXVM3-5K 48V inverter connected to 2 pylontech US3000C batteries. The inverter is set to only charge using solar power. But for some stupid reason it's still using grid to charge. I only noticed because my power bill went up. The inverter is also set to SUB but have now changed it to SBU with back to grid voltage set to 48V. Why would the inverter all of a sudden just start using grid power to charge even though it should not. I am running solar assistance via USB on a raspberry pi to monitor the inverter. I have recently updated the Solar Assistant to the latest version. I cannot recall that it did this on the previous version. Could this be a Solar Assistant issue or is there something going on with my inverter? Please help. The inverter is now pulling extra power for absolutely no reason and it's using the same amount of power in a month as my geyser. Also, I have 7kw/h of storage, but solar assistant says I only have 4.8kw/h. Are you sure your battery is charged enough not to trigger the back to grid level. Share your various inverter settings here and also indicate if the BMS is in charge. There must be a reason why SA gives a different capacity. Also try using without comms but make sure the bulk setting is 0.7V lower than the value given by Pylon. Do some charging under supervision to prevent over voltage. Quote Link to comment Share on other sites More sharing options...
Mau921020 Posted July 5 Author Share Posted July 5 (edited) I am sure the battery is charged enough. That was the first thing I checked when this started happening. I have also noticed that on the SBU setting when the inverter goes to full battery power the lights in my house flicker ever so slightly. If I set the inverter to SUB and then switch of grid power and the inverter goes to battery power the light DO NOT flicker. My inverter is connected with the neutral wire going to ground as well. I have also noticed that the battery voltage and state of charge drops overnight even though I was using grid power the whole night. See attachment labels Battery The battery 2 attachment shows that I only have 4.8 kWh of capacity, but I have 2x pylontech US3000C batteries. I don't know if the inverter is limiting the capacity, but I can't find any reason why it should. The settings tab shows that the batteries should only charge with solar. This has been the setting since I installed everything in 2021. The only setting that I'll changes is the SUB/SBU/USB setting. Edited July 5 by Mau921020 Quote Link to comment Share on other sites More sharing options...
Mau921020 Posted July 5 Author Share Posted July 5 On 2024/07/04 at 10:04 AM, Scorp007 said: Are you sure your battery is charged enough not to trigger the back to grid level. Share your various inverter settings here and also indicate if the BMS is in charge. There must be a reason why SA gives a different capacity. Also try using without comms but make sure the bulk setting is 0.7V lower than the value given by Pylon. Do some charging under supervision to prevent over voltage. I am sure the battery is charged enough. That was the first thing I checked when this started happening. I have also noticed that on the SBU setting when the inverter goes to full battery power the lights in my house flicker ever so slightly. If I set the inverter to SUB and then switch of grid power and the inverter goes to battery power the light DO NOT flicker. My inverter is connected with the neutral wire going to ground as well. I have also noticed that the battery voltage and state of charge drops overnight even though I was using grid power the whole night. See attachment labels Battery The battery 2 attachment shows that I only have 4.8 kWh of capacity, but I have 2x pylontech US3000C batteries. I don't know if the inverter is limiting the capacity, but I can't find any reason why it should. The settings tab shows that the batteries should only charge with solar. This has been the setting since I installed everything in 2021. The only setting that I'll changes is the SUB/SBU/USB setting. Quote Link to comment Share on other sites More sharing options...
Mau921020 Posted July 5 Author Share Posted July 5 On 2024/07/04 at 7:02 AM, Coulomb said: It could be a firmware issue. What is your present main (U1) firmware version? I am not sure what the firmware version is (I don't even know how to check), but the inverter was originally bought in 2019/2020 so will be an old version. I have looked but was never able to find new firmware versions for my inverter. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 6 Share Posted July 6 15 hours ago, Mau921020 said: I have also noticed that on the SBU setting when the inverter goes to full battery power the lights in my house flicker ever so slightly. Do you mean when you have full load (near 5 kW), or the battery approaches 100% SoC? Or do you mean when the inverter is in bypass mode, AC-in is removed, and the battery has to take over full supply of the load power? That requires switching the load from grid, to briefly unconnected, to the output of the inverter. The grid could be 10 VAC higher or lower than the 230 V of the inverter output. Quote If I set the inverter to SUB and then switch of grid power and the inverter goes to battery power the light DO NOT flicker. I think that would be because the inverter (DC -> AC converter) output was connected to the grid, and so was matched in amplitude and phase. There is also no brief "no load power" in this case, merely that the grid, which may or may not have been partially supporting the load, is disconncted. Quote My inverter is connected with the neutral wire going to ground as well. All modern Axperts have a relay that connects AC-out neutral to earth when the load is not connected to the grid. Is this what you mean? Or do you mean that you have connected neutral to earth somewhere other than the usual neutral to earth bond in the distribution board? If so, where? Quote I have also noticed that the battery voltage and state of charge drops overnight even though I was using grid power the whole night. So the battery is not being grid charged overnight. When is this grid charging happening? It's normal in SBU mode with no grid charging for the battery to discharge at night, powering loads. Even if the grid is powering the loads, then the inverter's internal consumption (some 50 W when inverting, for a 5 kVA model) is supplied by the battery, not the grid, whether the grid is present or not, at least for some models. I don't know about the VM III, sorry. Quote The battery 2 attachment shows that I only have 4.8 kWh of capacity, but I have 2x pylontech US3000C batteries. Are you certain that these are wired correctly? In particular, is there a small comms cable from on module to the other? Is the BMS cable on the master module? Are you certain that the DIP switches are set correctly in the battery modules? Quote I don't know if the inverter is limiting the capacity, but I can't find any reason why it should. The display firmware, or I assume also Solar Assistant if that's what is connected to the battery's BMS, will be relying on replies from the battery BMS to indicate the battery capacity. If the DIP switches or wiring is not correct, then the module with the BMS comms cable won't be aware of the other module. But a quick Google search indicates that the US3000C has a 3.55 kWh capacity, which means 4.8 kWh is too high for one module and too low for two modules. So maybe Solar Assistant isn't using the BMS information after all, and you need to tell it your battery capacity in a setting somewhere? It sounds like it thinks you have two US2000C modules (each 2.4 kWh of capacity). Quote Link to comment Share on other sites More sharing options...
Mau921020 Posted July 7 Author Share Posted July 7 (edited) On 2024/07/06 at 5:56 AM, Coulomb said: Or do you mean when the inverter is in bypass mode, AC-in is removed, and the battery has to take over full supply of the load power? That requires switching the load from grid, to briefly unconnected, to the output of the inverter. The grid could be 10 VAC higher or lower than the 230 V of the inverter output. This is when grid power and solar power is off and the house transitions from solar to battery power. The lights flicker ever so slightly. It does go away after time. On 2024/07/06 at 5:56 AM, Coulomb said: All modern Axperts have a relay that connects AC-out neutral to earth when the load is not connected to the grid. Is this what you mean? Or do you mean that you have connected neutral to earth somewhere other than the usual neutral to earth bond in the distribution board? If so, where? With this I mean that my inverter output Neutral is connected to the Earth I installed for the solar panel grounding. So there is a wire from the neutral output to the earth bus bar in the DB. My inverter does not have an internal bonding like that. I noticed this because the lights in my house would not turn fully off. Some would stay on. After I spoke to a solar electrician I made the bonding from neutral output of the inverter to the earth and the lights turned off completely when the switch was off. On 2024/07/06 at 5:56 AM, Coulomb said: So the battery is not being grid charged overnight. When is this grid charging happening? It's normal in SBU mode with no grid charging for the battery to discharge at night, powering loads. Even if the grid is powering the loads, then the inverter's internal consumption (some 50 W when inverting, for a 5 kVA model) is supplied by the battery, not the grid, whether the grid is present or not, at least for some models. I don't know about the VM III, sorry. So what I mean is that I'll have the inverter set to SUB and have only solar charge the batteries and use grid power and not battery power. In the morning there is sometimes a 10% drop in battery SOC even though I never used any battery power. The graphs show I only used grid power. On 2024/07/06 at 5:56 AM, Coulomb said: Are you certain that these are wired correctly? In particular, is there a small comms cable from on module to the other? Is the BMS cable on the master module? Are you certain that the DIP switches are set correctly in the battery modules? So I charged the new battery fully and made sure both batteries were fully charged before I connected the 2 together. I watched a couple of videos and was on this forum to do some research before I attempted to connect the 2 together. See attached picture. The bottom battery is the master. I have been wanting to run the batteries without the comms to the inverter but lost the setting. I did that when I had only 1 battery cuz I could not find the comms cable so eventually made a new one. On 2024/07/06 at 5:56 AM, Coulomb said: But a quick Google search indicates that the US3000C has a 3.55 kWh capacity, which means 4.8 kWh is too high for one module and too low for two modules. So maybe Solar Assistant isn't using the BMS information after all, and you need to tell it your battery capacity in a setting somewhere? It sounds like it thinks you have two US2000C modules (each 2.4 kWh of capacity). Yeah, that's what I also think. The batteries drain all the way so I think the reading might not be correct. I will investigate this further. I am just trying to figure out if this is normal or if there is something wrong. With loadshedding I never ran the inverter in SBU mode, only SUB mode so that the batteries are full for when loadshedding happens. So, I never noticed the flickering on the lights when the inverter went from solar to battery. This is one of my main concerns, but I think its noting and just that my inverter is not a "fancy" as other inverters. It does stop flickering when the sun is gone. Edited July 7 by Mau921020 Quote Link to comment Share on other sites More sharing options...
Coulomb Posted July 9 Share Posted July 9 On 2024/07/07 at 6:57 PM, Mau921020 said: This is when grid power and solar power is off and the house transitions from solar to battery power. The lights flicker ever so slightly. It does go away after time. Ah! I was somehow thinking that it was a single change of brightness. You seem to be talking about 15-30 minutes as the sun is setting that the brightness of lights goes up and down slightly. I've never noticed this myself, but I have the low PV voltage solar charger. I vaguely recall reports of this on the forums. I can't recall what the consensus was: normal, hardware fault, or firmware fault. Your Google is as good as mine. On 2024/07/07 at 6:57 PM, Mau921020 said: After I spoke to a solar electrician I made the bonding from neutral output of the inverter to the earth and the lights turned off completely when the switch was off. But now you presumably have two connections to earth when AC-in is connected to AC-out, which is all the time in SUB priority if grid is present, or in SBU priority when in bypass mode. Did you have the case of the inverter earthed before you made this bonding? Maybe you have a clone and it didn't copy the part of the circuit that earths AC-out only when AC-in is not connected to AC-out. That seems unlikely, but I suppose it's possible. Quote Link to comment Share on other sites More sharing options...
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