Gavin286 Posted October 7, 2022 Share Posted October 7, 2022 Hi folks, I noticed that the PV output drops to around 120w as soon as the batteries are charged even when the load is requiring power that PV can supply. I do understand if its a design thing, I just want to understand why it happens. It's only been doing this after adding another 15 panels. When it was only the 5, the system didn't do this. See attached pic. Thanks! Quote Link to comment Share on other sites More sharing options...
Arandoza Posted October 7, 2022 Share Posted October 7, 2022 Check your inverters MPPT max VOC and Panel configuration VOC ratings, check if you are not exceeding them? It maybe that you have exceeded them and the MPPT is clipping the panel output? Maybe add your panel and inverter specs to the post, it will probably be helpfull to others in giving suggestions? Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 Thanks for the reply. I'm not sure if its the voltage. Below are the specs, and when the drop occurred - 10:15am... Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 My panels are the 455w units Quote Link to comment Share on other sites More sharing options...
Kalahari Meerkat Posted October 7, 2022 Share Posted October 7, 2022 (edited) 17 minutes ago, Gavin286 said: My panels are the 455w units your 460V is above your MPPT range of 425V max, I'd try and not exceed 400V if possible, so, presumably you have 10S2P for the panels... maybe restring this lot into 6S3P and end up with a much lower voltage, but more likely will work betterer... else if you can get one more panel and have space for it 7S3P then, you won't end up with 2 spare panels... but the 2 spare panels will probably also be ok... Edited October 7, 2022 by Kalahari Meerkat Quote Link to comment Share on other sites More sharing options...
P1000 Posted October 7, 2022 Share Posted October 7, 2022 10 of those panels in series is too much for that inverter, you need to remove one per string. Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 Thanks for the help guys. I assumed it was 500v max. I'll get the electrician to split the strings into 4 - 2 per mppt. Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 Just out of interests' sake - what happens if I don't split the strings and I continually hit the max V? Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 7, 2022 Author Share Posted October 7, 2022 15 minutes ago, Kalahari Meerkat said: your 460V is above your MPPT range of 425V max, I'd try and not exceed 400V if possible, so, presumably you have 10S2P for the panels... maybe restring this lot into 6S3P and end up with a much lower voltage, but more likely will work betterer... else if you can get one more panel and have space for it 7S3P then, you won't end up with 2 spare panels... but the 2 spare panels will probably also be ok... They are wired 10 panels in series, 10 per mppt... Quote Link to comment Share on other sites More sharing options...
Jacques Ester Posted October 7, 2022 Share Posted October 7, 2022 You will blow your inverters MMPT Gavin286 and WannabeSolarSparky 2 Quote Link to comment Share on other sites More sharing options...
Kalahari Meerkat Posted October 7, 2022 Share Posted October 7, 2022 11 minutes ago, Gavin286 said: They are wired 10 panels in series, 10 per mppt... eventually the magic smoke will be let loose.. 5S4P is a good option otherwise as well... WannabeSolarSparky 1 Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted October 8, 2022 Share Posted October 8, 2022 (edited) On 2022/10/07 at 2:05 PM, Kalahari Meerkat said: your 460V is above your MPPT range of 425V max, I'd try and not exceed 400V if possible, so, presumably you have 10S2P for the panels... maybe restring this lot into 6S3P and end up with a much lower voltage, but more likely will work betterer... else if you can get one more panel and have space for it 7S3P then, you won't end up with 2 spare panels... but the 2 spare panels will probably also be ok... 3P as indicated will exceed the max PV input of 22A. 33A for 3P will be clipped to below 22A. This is a major loss of PV. Will 2P7S on MPPT1 and 1P7S on MPPT2 not be a better call or just use 2P for each MPPT. 5S2P for each MPPT.???? Edited October 12, 2022 by Scorp007 iiznh 1 Quote Link to comment Share on other sites More sharing options...
Kalahari Meerkat Posted October 8, 2022 Share Posted October 8, 2022 26 minutes ago, Scorp007 said: 3P as indicated will exceed the max PV input of 22A. 33A for 3P will be clipped to below 22A. This is a major loss of PV. Luckily how much current is allowed in is controlled by the inverter... tension on the other hand.... Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted October 8, 2022 Share Posted October 8, 2022 3 minutes ago, Kalahari Meerkat said: Luckily how much current is allowed in is controlled by the inverter... tension on the other hand.... Agree. But still the inverter will not allow more than 22A while 3P can provide 33A from the Imp. zsde 1 Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 12, 2022 Author Share Posted October 12, 2022 So an update on this: I've managed to get the suppliers to confirm that the voltage is too high. The electrician is still in denial and I'm basically having to force him to re-string the PV. Now here's the thing: Is it difficult to split the 2 sets of 10 panels into 2 strings each? As in labour / cost intensive? I was thinking I would just remove 1 panel from each string and sacrifice ±700w and either return or sell the 2 panels. the VOC of each panel is 49.5 Quote Link to comment Share on other sites More sharing options...
iiznh Posted October 12, 2022 Share Posted October 12, 2022 1 hour ago, Gavin286 said: Now here's the thing: Is it difficult to split the 2 sets of 10 panels into 2 strings each? As in labour / cost intensive? It should not be labour intensive. But it depends on your roof and where strings are located. If they are all on the same roof it might be as simple as re-plugging MC4 connectors and adding a 2xMC4 splitters What size PV cabling and what is the distance? I used 6mm cable, running 4S2P for one string(I have plenty issues with large trees shading parts of my string). And 5S for the other. I think this is a good solution: On 2022/10/08 at 9:53 PM, Scorp007 said: Will 2P7S on MPPT1 and 1P7S on MPPT2 not be a better call or just use 2P for each MPPT. 5S2P for each MPPT. I would go with 7S2P (14 panels) for string 1 and 6S for string 2. I have no idea what your consumption is like, but I assume you got 20 panels to cover your needs. If you are already generating excess power that is not used then you might be better off having 2x strings of 9S and sell the 2 panels like you suggested Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 12, 2022 Author Share Posted October 12, 2022 8 minutes ago, iiznh said: It should not be labour intensive. But it depends on your roof and where strings are located. If they are all on the same roof it might be as simple as re-plugging MC4 connectors and adding a 2xMC4 splitters What size PV cabling and what is the distance? I used 6mm cable, running 4S2P for one string(I have plenty issues with large trees shading parts of my string). And 5S for the other. I think this is a good solution: I would go with 7S2P (14 panels) for string 1 and 6S for string 2. I have no idea what your consumption is like, but I assume you got 20 panels to cover your needs. If you are already generating excess power that is not used then you might be better off having 2x strings of 9S and sell the 2 panels like you suggested I have 10 on one roof separated by a small elevation, and the other 10 on the top side. All 20 are on the same side (North facing). The issue is that the 1 set of 10 is on a roof that has a vaulted ceiling and there is no access to the under side of the tile. The other 10 are in a traditional ceiling that is easy. The PV only supplies max 6kw which is my demand. I have to turn stuff on to use the power generated. We got extra panels to compensate for cloudy / rainy days, but losing 2 panels I don't think will make that much diff. FYI both strings are in S so I would assume its a matter of un coupling 1 panel on each string and bob's your uncle. Quote Link to comment Share on other sites More sharing options...
iiznh Posted October 12, 2022 Share Posted October 12, 2022 16 minutes ago, Gavin286 said: FYI both strings are in S so I would assume its a matter of un coupling 1 panel on each string and bob's your uncle. Yes, if the strings are not next to each other then this would be the easiest solution by far. Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 12, 2022 Author Share Posted October 12, 2022 4 minutes ago, iiznh said: Yes, if the strings are not next to each other then this would be the easiest solution by far. Thanks. I wonder how much I could sell the panels for... Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted October 12, 2022 Share Posted October 12, 2022 (edited) 9 hours ago, Gavin286 said: Thanks. I wonder how much I could sell the panels for... As long as your price is not higher than new panels. I see guys trying to sell 2nd hand equipment at a higher price than current new price. I doubt one should pitch the price on what you paid. This is very true for panels bought 5 years ago when panels were much more expensive than now. Edited October 12, 2022 by Scorp007 Gavin286 and zsde 2 Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 28, 2022 Author Share Posted October 28, 2022 Hey folks, So just an update on this issue if anyone runs into the same or similar issue. My inverter was set to max charging current of 100a which is fine since I have 2x 5.1kwh batts that can both charge at 100a each. I have discovered that by dropping that max current to 50a, I do still get a voltage increase (however not a spike anymore), and the PV supplies the load straight away. Note also that my charge time has only increased by roughly 20 minutes! Previously it would bottom out to ±100w and then take about an hour to slowly ramp up to match the load requirement. I assume with my 0.5% knowledge of electricity, perhaps this fits into the laws of electricity IE voltage / amperage etc have to be friends to work nicely together And today the electrician is coming to remove 1 panel from each string down to 9 per string in S. This should drop the voltage down by 45v or so to keep within spec of the 425v max recommended per mppt. Quote Link to comment Share on other sites More sharing options...
Kalahari Meerkat Posted October 28, 2022 Share Posted October 28, 2022 22 minutes ago, Gavin286 said: And today the electrician is coming to remove 1 panel from each string down to 9 per string in S. This should drop the voltage down by 45v or so to keep within spec of the 425v max recommended per mppt. Glad you got it to behave a bit better in the meantime. Going down to 9 series panels is the safer option, this will give you, as per the specs of the panels 418.5V open circuit V and this should be ok and you shouldn't notice the 2 X 455Wp missing, after all you still have 2 X 4095Wp remaining. Quote Link to comment Share on other sites More sharing options...
Gavin286 Posted October 28, 2022 Author Share Posted October 28, 2022 1 minute ago, Kalahari Meerkat said: Glad you got it to behave a bit better in the meantime. Going down to 9 series panels is the safer option, this will give you, as per the specs of the panels 418.5V open circuit V and this should be ok and you shouldn't notice the 2 X 455Wp missing, after all you still have 2 X 4095Wp remaining. Agreed. So far I haven't required a load of more than 6kw at a time, so there is good future expansion, but at a cost of perhaps too many panels. Oh well, its done already Thanks for the reply! zsde 1 Quote Link to comment Share on other sites More sharing options...
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