August 25, 20205 yr Good day to all powerforum users. I have a weird problem on my Axpert King Inverter. The solar output Kw that's coming from my solar panels seems to be to low. If I calculate the value manually by taking the PV Voltage and multiplying it with the Amps that the panels are giving out. ( Measured with a amp probe) I should then get the KW coming from the panels, right? But on the inverter that value is much lower. It seems like there is some big losses somewhere, I thought that the amps showing on the inverter was after the MPPT done it's job but the value is exactly the same as the value on the amp probe measured at the PV combiner. I have attached some images explaining my situation. Maybe firmware related? Any help would be greatly appreciated!
August 26, 20205 yr 21 hours ago, jannes258 said: If I calculate the value manually by taking the PV Voltage and multiplying it with the Amps that the panels are giving out. ( Measured with a amp probe) I should then get the KW coming from the panels, right? If you divide by 1000 to bring to kilo watts, yes. 21 hours ago, jannes258 said: But on the inverter that value is much lower. In your photos, I see 28 A (into the battery, not from the panels), and guessing the battery voltage to be 50.3 V, that would be 50.3 x 28 = 1410 W = 1.41 kW, as it displays. Are you claiming that you measure more than 28 A from the panels? In fact, you should see around 1410 / 74 = 19 A, otherwise, your inverter-charger is violating the law of conservation of energy (and power). Solar charge controllers are about 98% efficient.
August 26, 20205 yr Author Hi Coulomb Thank you! I actually thought that might be the case, quite interesting as the VMiii inverters with the higher MPPT Input Voltage actually shows the PV KW's that's coming from the panels itself. The current that's coming from the panels on the inverter as well as the amp probe measured the same, just thought that the input PV of 1.41KW was the power that the panels itself produced. (Charging the battery and powering the loads, the total KW that the panels were delivering) Thanks for confirming!
August 27, 20205 yr 21 hours ago, jannes258 said: VMiii inverters with the higher MPPT Input Voltage actually shows the PV KW's that's coming from the panels itself. I believe that all models do that.
August 29, 20205 yr Author I see that the VMiii uses the solar amps times the solar volts to get the solar W/KW. Where the King uses the solar amps times the battery volts to get the solar W/KW. Wouldn't the solar amps times the solar volts be the most accurate reading of solar W/KW?
August 30, 20205 yr 4 hours ago, jannes258 said: Where the King uses the solar amps times the battery volts to get the solar W/KW. That would be battery-side PV current, not panel current. 4 hours ago, jannes258 said: Wouldn't the solar amps times the solar volts be the most accurate reading of solar W/KW? It depends on what you are interested in. Often you want to know how much the PV is charging the battery, not what the panels are producing. Though with some 98% efficiency, the power is nearly the same anyway.
September 1, 20205 yr Hi Please assist. My system has been running stable for a few months now, with the odd PV loss issue occasionally. However, since about 3 days ago I have seen a major loss in PV during the day when the sun is shining. It climbs briefly to over 3000w produced, but then dwindles down to below 100w and floats there for the whole day (from a 3900w array) with an occasional spike in production. System consist of a Voltex King 5KVa, 10Kw LifePo4 lithium batteries with built in BMS, 12 x 330w PV Any ideas??
September 1, 20205 yr 32 minutes ago, KobusC said: Any ideas?? As a first step, please try changing your 'AC input range' to Appliance. The UPS setting can sometimes cause it to only run on batteries If that does not help, please also post your battery settings and battery graphs pages
September 2, 20205 yr 23 hours ago, KobusC said: 12 x 330w PV My guess is that these are wired 3S4P, and the PV voltage is too high, causing the SCC to overheat and/or derate power due to voltage. Rewiring to 2S and 6P would fix it, at considerable hassle. Can you isolate all but one of the PV strings? That should eliminate SCC temperature as a confounding variable. If it still derates (relative to what you can realistically expect from one string of panels), then rewire just that string as 2S and see if it behaves better (again, comparing with what you can realistically expect from 2 panels). If 2 panels is better, then rewire all the panels.
September 10, 20205 yr On 2020/09/02 at 3:31 PM, Coulomb said: My guess is that these are wired 3S4P, and the PV voltage is too high, causing the SCC to overheat and/or derate power due to voltage. Rewiring to 2S and 6P would fix it, at considerable hassle. Can you isolate all but one of the PV strings? That should eliminate SCC temperature as a confounding variable. If it still derates (relative to what you can realistically expect from one string of panels), then rewire just that string as 2S and see if it behaves better (again, comparing with what you can realistically expect from 2 panels). If 2 panels is better, then rewire all the panels. Hi, thanks for all the advice. System now again running 100% for past week without making any changes. Will leave as is for now and hope for best!
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