June 15, 20233 yr good afternoon Living here in the uk the winter months can be a tad grim. So my 8kw sunsynk inverter is using most if not all the power just to keep itself running. id like to add more panels if possible. id like to put 12x390w panels on each MPPT When calculating the max voltage of a solar panel string.. what should I us? Maximum power voltage VMP or Open circuit Voltage. VOC Thanks in advance
June 15, 20233 yr 20 minutes ago, ALUk said: good afternoon Living here in the uk the winter months can be a tad grim. So my 8kw sunsynk inverter is using most if not all the power just to keep itself running. id like to add more panels if possible. id like to put 12x390w panels on each MPPT When calculating the max voltage of a solar panel string.. what should I us? Maximum power voltage VMP or Open circuit Voltage. VOC Thanks in advance Vmp is important but not as crucial as voc. It's important to work on the controllers maximum allowed voltage as it can be damaged or destroyed if it is exceeded.
June 15, 20233 yr 32 minutes ago, ALUk said: good afternoon Living here in the uk the winter months can be a tad grim. So my 8kw sunsynk inverter is using most if not all the power just to keep itself running. id like to add more panels if possible. id like to put 12x390w panels on each MPPT When calculating the max voltage of a solar panel string.. what should I us? Maximum power voltage VMP or Open circuit Voltage. VOC Thanks in advance Voc. What size and how many panels have you connected at the moment. Voc in the specs is at 25 deg C. It increases by about 0.3% per degree. Thus use the expected min temp to calculate. Voc of panels at 25 degrees around 425V I guess. Edited June 15, 20233 yr by Scorp007
June 16, 20233 yr Author I have 10x390w. Trina panels south facing on 1 MPPT. and 8 of the same laid flat on garage roof on second MPPT. would like increase to 12 on each MPPT if possible?
June 16, 20233 yr 12 of those panels in series on each string will exceed the inverters max input voltage and could end up blowing some electronics on the inverter. 12 X 40.8 = 489.6V > 425V ( Suggested safe MAX V ) If you want to do 12 of those panels on each mppt then you can do 6 in series + 2 sets of 6 in parallel on each mppt Edited June 16, 20233 yr by WannabeSolarSparky
June 16, 20233 yr Do you not have more space on the south roof to add more there than the string lying flat? Having 7 in series in 2 parallel strings on one MPPT and 10 in series on the flat roof to the 2nd MPPT could also work. One can also increase the above 7 in series to 8S2P on south roof and 8 lying flat will also provide a good yield. Even 9S2P. One wants to have the flat panels at a minimum. For us in sunny ZA it's unthinkable that your current setup feeds about just the inverter self consumption.
June 16, 20233 yr Author I have 10x390w. Trina panels south facing on 1 MPPT. and 8 of the same laid flat on garage roof on second MPPT.
June 16, 20233 yr Author I have room for 2 or 3 more south facing could go on kitchen roof. then I have room for 4 or 5 west facing. I have a east facing roof but as it’s at the front of the bungalow I wasn’t going to fit panels on it. In the winter months I fill up my 200w battery bank with overnight off peak electricity. then on dull days of which there are many. I find more power coming from the battery than the house is using. the inverter consumes more that it produces. December photo attached.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.