July 20, 20233 yr Author 50 minutes ago, zsde said: I did contact Amos, their International Rep. None of the three versions of this model can parallel without having hardware (comms board) changes done. 🙈
July 20, 20233 yr On 2023/07/17 at 9:35 PM, L_D said: If I were to add 10 panels it would give me 6050W and 415VDC EDIT: With a temperature coefficient of Voc of -0.26 % / deg C then you are good to go with 10s1p string configuration even at 0 deg C. Temp Deg C Factor 10s1p Voc 10s1p Vmp 0 1.065 441.97 373.82 5 1.052 436.58 369.25 10 1.039 431.18 364.69 15 1.026 425.79 360.13 20 1.013 420.40 355.56 25 1.000 415.00 351.00 Remember to apply a correction factor for Voc depending on the lowest expected ambient temperature. If temps drop to between 4 and 0 deg C in winter then the combined Voc should not exceed 450/1.10 = 409Voc. This effectively limits you to 9 panels in series. Edited July 20, 20233 yr by Kilowatt Power A more accurate correction factor for Voc based on the corresponding datasheet
July 21, 20233 yr Author On 2023/06/23 at 5:22 PM, zsde said: I have the same Inverter, albeit the original version with Firmwares 040 and 041 There have been two sneaky model updates since with different firmwares, but the model number never changed and the firmwares are not interchangeable, in fact, you cannot even parallel them unless they are the same version. The original version had an 18A max for the MPPT. With the last Firmware update that was increased to 22A. Not sure if these latest models are also base 18A or whether they come with 22A with their factory released Firmware. The max PV input is 6000W. With my Panel config I get around 255V under load max per string, at a clipped 22A that equates to ~5600W and I have only seen that once or twice in 2 years. Although the manual states 450V VoC max, the MPPT operating range is 120-430Vdc. The max voltage should not be exceeded. The MPPT can't clip excess voltage. The electrician says he connects two strings of 5 into a combiner box with surge arrest and fuses. He says he has never connected 10 panels in series, always does two balanced strings. Can you connect two strings into a combiner box without exceeding the current?
July 21, 20233 yr 18 minutes ago, L_D said: The electrician says he connects two strings of 5 into a combiner box with surge arrest and fuses. He says he has never connected 10 panels in series, always does two balanced strings. Can you connect two strings into a combiner box without exceeding the current? Evidently your electrician is not conversant with high voltage MPPT controllers. Sorry to say. Consider getting another qualified installer to show him how it's done.
July 21, 20233 yr 33 minutes ago, L_D said: The electrician says he connects two strings of 5 into a combiner box with surge arrest and fuses. He says he has never connected 10 panels in series, always does two balanced strings. Can you connect two strings into a combiner box without exceeding the current? May be he did it this way with 270-300W panels. Doing it with 600W panels there will be a about 40% clipping of the PV current. The inverter can only use 22A.
July 21, 20233 yr 2 hours ago, L_D said: The electrician says he connects two strings of 5 into a combiner box with surge arrest and fuses. He says he has never connected 10 panels in series, always does two balanced strings. Can you connect two strings into a combiner box without exceeding the current? Sorry, it's not good enough to say "That's how I've always done it." You have to look at the specs of the panels in relation to the inverter, and do some basic maths. Ask your installer to read through this thread, and if he cannot understand the responses that people have given to you, find someone who does. Edited July 21, 20233 yr by GreenFields
July 21, 20233 yr Author 1 hour ago, Kilowatt Power said: Evidently your electrician is not conversant with high voltage MPPT controllers. Sorry to say. Consider getting another qualified installer to show him how it's done. So the best for my setup given the Growatt limitations (1MPPT, 18A max, 120V~430V) would be to connect 10 panels in serie to a 1 string combiner box. That gives met 6050W, 17.2A and 415V 🤷🏼♂️
July 21, 20233 yr 19 minutes ago, L_D said: So the best for my setup given the Growatt limitations (1MPPT, 18A max, 120V~430V) would be to connect 10 panels in serie to a 1 string combiner box. That gives met 6050W, 17.2A and 415V 🤷🏼♂️ The answer is a resounding YES on condition that the lowest expected ambient temperature does not drop below 0 deg C Edited July 21, 20233 yr by Kilowatt Power
July 21, 20233 yr 34 minutes ago, L_D said: So the best for my setup given the Growatt limitations (1MPPT, 18A max, 120V~430V) would be to connect 10 panels in serie to a 1 string combiner box. That gives met 6050W, 17.2A and 415V 🤷🏼♂️ Personally I'd go with 9 in series with this panel to stay well clear of the Voltage and Power limits under all conditions. The temperature increase on Voc of 0.25%/°C below 25 would especially bother me. Maybe it's never an issue, but I'd err on the side of caution, that's just me.
July 21, 20233 yr 1 hour ago, L_D said: So the best for my setup given the Growatt limitations (1MPPT, 18A max, 120V~430V) would be to connect 10 panels in serie to a 1 string combiner box. That gives met 6050W, 17.2A and 415V 🤷🏼♂️ If the 2 string combiner box is used the 4 wires to panels are just bridged to make the series string. 5min job.
July 21, 20233 yr Author 15 hours ago, Kilowatt Power said: EDIT: With a temperature coefficient of Voc of -0.26 % / deg C then you are good to go with 10s1p string configuration even at 0 deg C. Temp Deg C Factor 10s1p Voc 10s1p Vmp 0 1.065 441.97 373.82 5 1.052 436.58 369.25 10 1.039 431.18 364.69 15 1.026 425.79 360.13 20 1.013 420.40 355.56 25 1.000 415.00 351.00 Remember to apply a correction factor for Voc depending on the lowest expected ambient temperature. If temps drop to between 4 and 0 deg C in winter then the combined Voc should not exceed 450/1.10 = 409Voc. This effectively limits you to 9 panels in series. Are these low temperature corrections applied to Canadian Solar Hiku7 panels? Different panel manufacturers and models behave differently? Given the concern this is what my VoC would look like for 10 vs 9 panels: This is some preliminary info I could get on my panels: Solar panels are tested for their efficiency at 25°C. The ratio of the change of electrical performance when the temperature of the pv panel (or array) is decreased (or increased) by multiples of 1°C, relative to its quoted 25°C STC reference temperature. So given the Candian solar spec, my VOC would decrease with 0,26% for every degree lower than 25°C, and not increase as you have stated in your reply? Edited July 21, 20233 yr by L_D
July 21, 20233 yr 46 minutes ago, L_D said: So given the Candian solar spec, my VOC would decrease with 0,26% for every degree lower than 25°C, and not increase as you have stated in your reply? No it is not decrease but INCREASE. That is what the would debate is about as per your tables shown.
July 21, 20233 yr Author 13 minutes ago, Scorp007 said: No it is not decrease but INCREASE. That is what the would debate is about as per your tables shown. Hi scorp, the Canadian Solar spec states -0.26% for every degree more or less than the optimal 25 degrees? Why are you saying an increase if the temperature dips below 25? My total VOC at zero degrees sum would then be Total VoC (415) * (1-(24*0.26) =415 * 0.937 =388.85 Edited July 21, 20233 yr by L_D
July 21, 20233 yr 5 minutes ago, L_D said: Hi scorp, the Canadian Solar spec states -0.26% for every degree more or less than the optimal 25 degrees? Why are you saying an increase if the temperature dips below 25? My total VOC at zero degrees sum would then be: Total VoC (415) * (100-(24*0.26) =415 * 0.937 =388.85 Other way around. Double negative is a positive. A negative change in temperature multiplied by a negative percentage adjustment gives you a positive change in Voltage. The colder it gets, the more your panel Voltage goes up. With 10 panels you may be fine for a while, but chances are high there will come a day when you won't be.
July 21, 20233 yr 39 minutes ago, L_D said: Hi scorp, the Canadian Solar spec states -0.26% for every degree more or less than the optimal 25 degrees? Why are you saying an increase if the temperature dips below 25? My total VOC at zero degrees sum would then be Total VoC (415) * (1-(24*0.26) =415 * 0.937 =388.85 Refer to the minus sign at the co-efficient for power and voltage. This means increase with decreasing temperature. Your Canadian panels cannot work against physics. All panels have the increase and it is one of the most important metrics to look at as the MPPT will just set off the smoke bomb if you exceed the maximum voltage on cold days. Refer to the double minus being plus as @GreenFields explained. You left out the minus in the 0.26% in your calculation. Edited July 21, 20233 yr by Scorp007
July 21, 20233 yr Without using the temp correction factor chart i normally add 8.8% to panel array voc@stc and ensure it doesn't exceed Mppt max input. From 24deg C to minus 10 deg C it is 34 decrements in temperature. 34 x 0.26%/degC = 8.84%. Unlikely for temps to go below minus 10 degC in SA unless you stay in Sutherland. So yes i agree with @GreenFields 9 panels in series would be the safe option. 430-8.8%,=392v will be the sweet spot.
July 21, 20233 yr 1 hour ago, TaliaB said: Without using the temp correction factor chart i normally add 8.8% to panel array voc@stc and ensure it doesn't exceed Mppt max input. From 24deg C to minus 10 deg C it is 34 decrements in temperature. 34 x 0.26%/degC = 8.84%. Unlikely for temps to go below minus 10 degC in SA unless you stay in Sutherland. So yes i agree with @GreenFields 9 panels in series would be the safe option. 430-8.8%,=392v will be the sweet spot. So it's at least 3 arses that need to be kicked as from Tuesday 3+ of us feel that 9 in series is the safe bet to use. 😀😀
July 21, 20233 yr 4 hours ago, L_D said: Are these low temperature corrections applied to Canadian Solar Hiku7 panels? Different panel manufacturers and models behave differently? Given the concern this is what my VoC would look like for 10 vs 9 panels: This is some preliminary info I could get on my panels: Solar panels are tested for their efficiency at 25°C. The ratio of the change of electrical performance when the temperature of the pv panel (or array) is decreased (or increased) by multiples of 1°C, relative to its quoted 25°C STC reference temperature. So given the Candian solar spec, my VOC would decrease with 0,26% for every degree lower than 25°C, and not increase as you have stated in your reply? Excerpt from the CanadianSolar CS1V-MS Series Installation Manual The temperature coefficient of Voc for your panel is -0.26 % / °C At 0°C Correction factor = 1-(-0.26/100)*(25-0) = 1.065 10s1p Voc will then be 1.065 * 415 Voc = 441.98 Voc At -10°C Correction factor = 1-(-0.26/100)*(25--10) = 1.091 10s1p Voc will then be 1.091 * 415 Voc = 452.77 Voc And 9s1p Voc will be 1.091 * 373.5 Voc = 407.49 Voc If -10°C is the lowest expected ambient temperature at the installation site then it's safer to go with a 9s1p string configuration. PS: In my part of the world, the day/night temperature typically varies from 22/13°C to 27/16°C and is rarely below 10°C or above 30°C over the course of the year.
July 21, 20233 yr 1 hour ago, Kilowatt Power said: At 0°C Correction factor = 1-(-0.26/100)*(25-0) = 1.065 10s1p Voc will then be 1.065 * 415 Voc = 441.98 Voc Agree @Kilowatt Power the formula works and also agree the calculation above or below is installation site depandand, minus 10 and below for Sutherland. At 0°C 10s1p 25 x 0.26= 6.5%. 415 Voc +6.5% = 441.97v @ 0°C At 2°C 10s1p 23 x 0.26= 5.98%. 415 Voc +5.98% = 439.81v @ 2°C. At 2°C 9s1p 23 x 0.26= 5.98%. 373.5Voc+5.98% =395.83v @ 2°C. Edited July 21, 20233 yr by TaliaB Corrected calculation
July 22, 20233 yr On 2023/07/21 at 2:13 PM, L_D said: Are these low temperature corrections applied to Canadian Solar Hiku7 panels? Different panel manufacturers and models behave differently? Given the concern this is what my VoC would look like for 10 vs 9 panels: This is some preliminary info I could get on my panels: Solar panels are tested for their efficiency at 25°C. The ratio of the change of electrical performance when the temperature of the pv panel (or array) is decreased (or increased) by multiples of 1°C, relative to its quoted 25°C STC reference temperature. So given the Candian solar spec, my VOC would decrease with 0,26% for every degree lower than 25°C, and not increase as you have stated in your reply? Temp has an inverse relationship to VOC (- coefficient) and a direct relationship to ISC (+ coefficient), meaning as temp goes down the voc goes up and the isc goes down.
August 2, 20233 yr Author To @GreenFields, @Kilowatt Power, @Scorp007 and anyone else I might have missed, thank you very much for the very insightfull information on the panel efficiency and what I should install given my setup. Your contributions are pinpoint and valuable!
August 29, 20232 yr Author On 2023/07/22 at 10:28 PM, Zombie said: Temp has an inverse relationship to VOC (- coefficient) and a direct relationship to ISC (+ coefficient), meaning as temp goes down the voc goes up and the isc goes down. Just one last tecnical question in the Voltage. Calculations have been based off the VoC, but that is without any load and not like it will ever be used. Is it not more realistic to be using the lower Vmp value where there is load and a lower value that is representative of real world use?
August 29, 20232 yr 42 minutes ago, L_D said: Just one last tecnical question in the Voltage. Calculations have been based off the VoC, but that is without any load and not like it will ever be used. Is it not more realistic to be using the lower Vmp value where there is load and a lower value that is representative of real world use? Partly correct. Before the MPPT switches on when current can flow it will be at Voc. Say the start voltage is below the start due to bird casting a show. The moment they are gone the voltage will rise but the MPPT takes a few seconds to start up. These few seconds over the Voc is enough to ignite the smoke bomb. This is also real world. Rather save......... Below and example. Voc at 135V with MPPT off. When it adds load after switching on the voltage drops to 110V. Then a while later the MPPT is off again and voltage rises. This can easily happen when there is no load on the inverter and or battery is fully charged.
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