February 17, 20251 yr Happens every time the battery is discharged, for example in the graph below; at around 02:40, with consumption (orange) continuing at the same background level, the SOC (purple line) drops from around 14% to ZERO, WITHOUT ANY CORRESPONDING CHANGE IN CONSUMPTION OR EXPORT. It then charges to 6% SOC, which is as per the set minimum level, by around 03:20. Any help or advice would be appreciated Edited February 17, 20251 yr by PhilT
February 17, 20251 yr When asking questions like this, it's beneficial to include all the important info. Otherwise it's pretty hard to answer correctly. For this case: OK, purple is SOC and right axis would be SOC%. What is Orange, Blue, Green, Red? What are the Units on the left axis kW? How do you measure each of the metrics? How do you get SOC values, from BAT Voltage or from BMS? What are we talking about, hybrid PV, off-grid PV, Server UPS or a coal Power Plant? What are the parameters of the system? Why did you designed the system in a way that it discharges battery to 6% every day?
February 17, 20251 yr Author 3 minutes ago, Youda said: When asking questions like this, it's beneficial to include all the important info. Otherwise it's pretty hard to answer correctly. For this case: OK, purple is SOC and right axis would be SOC%. What is Orange, Blue, Green, Red? What are the Units on the left axis kW? How do you measure each of the metrics? How do you get SOC values, from BAT Voltage or from BMS? What are we talking about, hybrid PV, off-grid PV, Server UPS or a coal Power Plant? What are the parameters of the system? Why did you designed the system in a way that it discharges battery to 6% every day? Hi thanks for the quick response, I'll try to answer as much as I know. Orange is consumption, red is mains import/export, blue is battery charge. Left axis is watts power. I believe the measurements are all via clamp meters. Not sure about SOC. It's a dedicated battery inverter. Not sure what parameters, give me an example. 6% SOC was the default minimum level set on installation - I haven't changed that.
February 17, 20251 yr 2 minutes ago, PhilT said: Not sure what parameters, give me an example. Make, model and power of the inverter. Make, model and capacity of the batteries. Is there a data communication cable betweeen the inverter and the batteries. Are you able to see individual cell voltages somewhere in the GUI or the APP where you got that chart from. Whether there are photovoltaic panels connected to the inverter, directly or via another AC coupled inverter, for example. 5 minutes ago, PhilT said: 6% SOC was the default minimum level set on installation Allowing discharge down to 6% is really heavy use of the batteries. It's great for squeezing maximum from the batteries, but might hurt them (depends on cell chemistry) if is happening regularly.
February 17, 20251 yr Something's a bit odd there. About 1:45 we see the battery SOC start climbing, but with no change of consumption, feed from the grid, nor any PV (understandable at that time of day). So how does SOC increase under those circumstances? Clearly firmware on the inverter is doing some guestimation, but you can't rely on what it supplies.
February 17, 20251 yr I'm going to take a flyer on this. Voltronics based inverter with Lithium based batteries with no comms.
February 17, 20251 yr Author 5 hours ago, Youda said: Make, model and power of the inverter. Make, model and capacity of the batteries. Is there a data communication cable betweeen the inverter and the batteries. Are you able to see individual cell voltages somewhere in the GUI or the APP where you got that chart from. Whether there are photovoltaic panels connected to the inverter, directly or via another AC coupled inverter, for example. Allowing discharge down to 6% is really heavy use of the batteries. It's great for squeezing maximum from the batteries, but might hurt them (depends on cell chemistry) if is happening regularly. Lux ACS Inverter + 3.2kw Greenlinx battery There's some cables but not sure if one is a data cable. The app gives a lot of detail but not individual cell voltages, only the total There are no photovoltaic panels connected to the battery inverter, directly or indirectly
February 17, 20251 yr Author 6 hours ago, Bobster. said: Something's a bit odd there. About 1:45 we see the battery SOC start climbing, but with no change of consumption, feed from the grid, nor any PV (understandable at that time of day). So how does SOC increase under those circumstances? Clearly firmware on the inverter is doing some guestimation, but you can't rely on what it supplies. yes that's another little oddity but I checked back a long way and it seems to be a one off, or extremely rare, whereas the subject of this thread happens after every discharge
February 17, 20251 yr 26 minutes ago, PhilT said: There are no photovoltaic panels connected to the battery inverter, directly or indirectly Another electricity waste ups setup 🤨
February 17, 20251 yr Author found the specs GreenLinx 3200 Model LV-L3.2-1P Nominal Capacity 3.2kWh Usable Capacity 3.2kWh Cell Type LFP(LiFeP04) Depth of Discharge 100% Operating Voltage Range 48 to 57.6V Nominal Voltage 51.2V Nominal Charging Current 40A Nominal Discharging Current 60A Max.Continuous Discharging Current IOOA Weight 34.9Kg Dimension 484*302*165mm Operating Temperature Charge: From o to 50c Discharge: From -10 to 50c Humidity Cooling Type Natural IP rating of enclosure IP54 Warranty 10years Communication Port CAN/RS485
February 17, 20251 yr 39 minutes ago, PhilT said: Lux ACS Inverter + 3.2kw Greenlinx battery There's some cables but not sure if one is a data cable. The app gives a lot of detail but not individual cell voltages, only the total There are no photovoltaic panels connected to the battery inverter, directly or indirectly Issue identified. Will reply in the evening.
February 17, 20251 yr 8 hours ago, PhilT said: Happens every time the battery is discharged, for example in the graph below; at around 02:40, with consumption (orange) continuing at the same background level, the SOC (purple line) drops from around 14% to ZERO, WITHOUT ANY CORRESPONDING CHANGE IN CONSUMPTION OR EXPORT. It then charges to 6% SOC, which is as per the set minimum level, by around 03:20. Any help or advice would be appreciated Hi @PhilT based on all your info, this should be the battery and inverter you have: Now, back to your chart: #1) Is rougly 2000W of AC load #2) Is the discharge, running for cca 1,5hrs (= 3kWh discharged). Since it's LFP chemistry, and the curve is nicely straight, it's definitely data provided by BMS that is integrating current over time in order to calculate SOC. At 1:30 there's just 0,4kWh stored in the battery, which is almost nothing. Note that your battery has 3,4kWh in reality, but usable is 3,2kWh and BMS is set by the factory to report SOC=0% once you've depleted 3,2kWh. That's why they can guarantee you to use whole 0-100% range, since technically the battery is 0,2kWh + 0-100%. #3) Is the point where BMS of the battery realized that the voltage of LPF cells raised back (becase the huge load was removed) and therefore it "corrected" it's SOC calculation. That was a mistake. In reality, the energy has been consumed and the real SOC should follow ORANGE highlight (#5). #4) is the point where voltage of the battery dropped slowly under a factory-defined threshold where BMS again "corrected" SOC calculation to ZERO and initiated recharge from the grid. Summary: It's normal for LFP cells that their voltage goes down and up based on the load, if that is quite high, relative to the cell capacity. The nominal battery energy (3,2kWh) was already consumed when the BMS reported SOC=0%. Strange SOC curve is just an error produced by the BMS calculations and corrections. This might be fixed by a battery firmware update in the future, if the manufacturer decides to make one. I don't like the fact that specsheet of the battery allows charging to 3,6V (it's 16cell battery), but I hope that the warranty is long and will cover battery swelling. Apart from that, there's nothing really bad going on and I would say that the system is operating as designed. If you need more runtime, you have to add more batteries. Hope this helps. Edited February 17, 20251 yr by Youda
February 17, 20251 yr Author 42 minutes ago, Youda said: Hi @PhilT based on all your info, this should be the battery and inverter you have: Now, back to your chart: #1) Is rougly 2000W of AC load #2) Is the discharge, running for cca 1,5hrs (= 3kWh discharged). Since it's LFP chemistry, and the curve is nicely straight, it's definitely data provided by BMS that is integrating current over time in order to calculate SOC. At 1:30 there's just 0,4kWh stored in the battery, which is almost nothing. Note that your battery has 3,4kWh in reality, but usable is 3,2kWh and BMS is set by the factory to report SOC=0% once you've depleted 3,2kWh. That's why they can guarantee you to use whole 0-100% range, since technically the battery is 0,2kWh + 0-100%. #3) Is the point where BMS of the battery realized that the voltage of LPF cells raised back (becase the huge load was removed) and therefore it "corrected" it's SOC calculation. That was a mistake. In reality, the energy has been consumed and the real SOC should follow ORANGE highlight (#5). #4) is the point where voltage of the battery dropped slowly under a factory-defined threshold where BMS again "corrected" SOC calculation to ZERO and initiated recharge from the grid. Summary: It's normal for LFP cells that their voltage goes down and up based on the load, if that is quite high, relative to the cell capacity. The nominal battery energy (3,2kWh) was already consumed when the BMS reported SOC=0%. Strange SOC curve is just an error produced by the BMS calculations and corrections. This might be fixed by a battery firmware update in the future, if the manufacturer decides to make one. I don't like the fact that specsheet of the battery allows charging to 3,6V (it's 16cell battery), but I hope that the warranty is long and will cover battery swelling. Apart from that, there's nothing really bad going on and I would say that the system is operating as designed. If you need more runtime, you have to add more batteries. Hope this helps. I think I get the gist of it - many thanks!
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