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Post by smileypete on Nov 28, 2016 14:56:37 GMT
Probably find it's pretty low if the 250W panel is 'off angle' to the winter sun and/or the batts are newish.
If you're off grid then those in the same boat (metaphorically) would probably be jealous that you can fully charge/eq the batts without resorting to lengthy genny runs.
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Post by smileypete on Nov 28, 2016 15:14:08 GMT
John, There are advantages and disadvantage of wiring panels in series. The most important disadvantage is I understand and have seen, is that if panels are wired in a series run and one gets shaded or partially shaded it reduces the power and voltage from the whole series, almost totally. Something as small as a 1 inch shadow across the panel will do it. Try it when you get the panels, wire them in series, making sure they are in full light, measure the voltage output and then shade a part of one panel and repeat the voltage readings. I know you will be careful and observe normal safety when you do it. I would suggest wiring in parallel. As to paralleling two controller outputs, if the are going into an inverter or similar where there is no voltage feedback fine. If the two are feeding a battery then they act just like any charger and react to the battery voltage and one hopefully switch off and thus a reduction in the power available. I have seen two controller chopping and changing. I would suggest use a single controller. As for an MCB or something between the panels and the controller. It can be an advantage to be able to isolate the controller from the panels if you need to work on the system. A 2 pole switch is standardly installed on domestic installations for just that purpose. Ello Graham, you been causing trouble on the other channel? Anyway panels with 'bypass diodes' should suffer much less from shading problems, as the current from unshaded cells can bypass the shaded cells, but the cheap second hand solar panels from solar farms may omit these. Very much doubt MPPTs would 'fight' each other but you could try setting them to slightly different charge voltages I s'pose.
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Post by Deleted on Nov 28, 2016 15:21:56 GMT
Solar is a new field for me, never having had any dealings with it before (In my book, it's ok knowing the theory but there ain't nuffin like hands on experience) I was considering getting from Bimble as follows for a 24V system3 x 260 W panels an MPPT controller However I was thinking of getting the 60 A Outback MPPT controller Instead of the 40A MPPT controller that Bimble recommend for that number of panels (My reasoning behind the Outback controller was to allow for increasing the number of panels to 4 or even 6 at a later date) What does the panel think Am I being OTT with the controller ? (Existing battery bank is a fairly new 280 Ah bank of Varta LFD140 sealed leisure and existing inverter is a 1500W there are no plans to change these at the moment) John, There are advantages and disadvantage of wiring panels in series. The most important disadvantage is I understand and have seen, is that if panels are wired in a series run and one gets shaded or partially shaded it reduces the power and voltage from the whole series, almost totally. Something as small as a 1 inch shadow across the panel will do it. Try it when you get the panels, wire them in series, making sure they are in full light, measure the voltage output and then shade a part of one panel and repeat the voltage readings. I know you will be careful and observe normal safety when you do it. I would suggest wiring in parallel.
As to paralleling two controller outputs, if the are going into an inverter or similar where there is no voltage feedback fine. If the two are feeding a battery then they act just like any charger and react to the battery voltage and one hopefully switch off and thus a reduction in the power available. I have seen two controller chopping and changing . I would suggest use a single controller.As for an MCB or something between the panels and the controller. It can be an advantage to be able to isolate the controller from the panels if you need to work on the system. A 2 pole switch is standardly installed on domestic installations for just that purpose. I understand that the MPPT controllers are suited to an input voltage that is near their max permissible, achieved by connecting the panels in Series. This also allows for smaller cable to be utilised. I think it depends if significant shading is likely or not. I would agree that it is useful to be able to disconnect the panels from the controller.I try and do this when it is dark, or by covering the panels before disconnecting.
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Post by tonyqj on Nov 28, 2016 15:25:40 GMT
John, There are advantages and disadvantage of wiring panels in series. The most important disadvantage is I understand and have seen, is that if panels are wired in a series run and one gets shaded or partially shaded it reduces the power and voltage from the whole series, almost totally. Something as small as a 1 inch shadow across the panel will do it. Try it when you get the panels, wire them in series, making sure they are in full light, measure the voltage output and then shade a part of one panel and repeat the voltage readings. I know you will be careful and observe normal safety when you do it. I would suggest wiring in parallel. As to paralleling two controller outputs, if the are going into an inverter or similar where there is no voltage feedback fine. If the two are feeding a battery then they act just like any charger and react to the battery voltage and one hopefully switch off and thus a reduction in the power available. I have seen two controller chopping and changing. I would suggest use a single controller. As for an MCB or something between the panels and the controller. It can be an advantage to be able to isolate the controller from the panels if you need to work on the system. A 2 pole switch is standardly installed on domestic installations for just that purpose. Ello Graham, you been causing trouble on the other channel? Anyway panels with 'bypass diodes' should suffer much less from shading problems, as the current from unshaded cells can bypass the shaded cells, but the cheap second hand solar panels from solar farms may omit these. Ooh, you've just saved me the hasssle of writing the same thing. The great thing about series panels with an MPPT controller (IF the panels have bypass diodes) is that the controller will still track the lower voltage to maximise the output from the other panels. Unless the panel voltage is really high an MPPT controller can struggle to make much impact on parallel panels. As to controllers in parallel I've already given my opinion.
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Post by geo on Nov 28, 2016 15:26:00 GMT
John, There are advantages and disadvantage of wiring panels in series. The most important disadvantage is I understand and have seen, is that if panels are wired in a series run and one gets shaded or partially shaded it reduces the power and voltage from the whole series, almost totally. Something as small as a 1 inch shadow across the panel will do it. Try it when you get the panels, wire them in series, making sure they are in full light, measure the voltage output and then shade a part of one panel and repeat the voltage readings. I know you will be careful and observe normal safety when you do it. I would suggest wiring in parallel. As to paralleling two controller outputs, if the are going into an inverter or similar where there is no voltage feedback fine. If the two are feeding a battery then they act just like any charger and react to the battery voltage and one hopefully switch off and thus a reduction in the power available. I have seen two controller chopping and changing. I would suggest use a single controller. As for an MCB or something between the panels and the controller. It can be an advantage to be able to isolate the controller from the panels if you need to work on the system. A 2 pole switch is standardly installed on domestic installations for just that purpose. Ello Graham, you been causing trouble on the other channel? Anyway panels with bypass diodes should suffer less from shading problems, but the cheap second hand solar panels from solar farms may omit these. Doubt MPPTs would 'fight' each other but you could try setting them to slightly different charge voltages. I would love to meet this person called graham he has seemed to got you lot wound up. The name is Geo or Geoff not graham. I have seen the same effect with modern panels. As you say you could change the voltages on the controllers, but you still lose power when one cuts out, unless you have selected the panels so that they only supply a maximum current needed at the switch off point. If the panels sets between them are supplying the max current the battery will take at the switch off point you have lost the advantage the panels give free charge in part. Better I would suggest to use one controller and harvest all the power the battery will take.
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Post by tonyqj on Nov 28, 2016 15:28:44 GMT
John, There are advantages and disadvantage of wiring panels in series. The most important disadvantage is I understand and have seen, is that if panels are wired in a series run and one gets shaded or partially shaded it reduces the power and voltage from the whole series, almost totally. Something as small as a 1 inch shadow across the panel will do it. Try it when you get the panels, wire them in series, making sure they are in full light, measure the voltage output and then shade a part of one panel and repeat the voltage readings. I know you will be careful and observe normal safety when you do it. I would suggest wiring in parallel.
As to paralleling two controller outputs, if the are going into an inverter or similar where there is no voltage feedback fine. If the two are feeding a battery then they act just like any charger and react to the battery voltage and one hopefully switch off and thus a reduction in the power available. I have seen two controller chopping and changing . I would suggest use a single controller.As for an MCB or something between the panels and the controller. It can be an advantage to be able to isolate the controller from the panels if you need to work on the system. A 2 pole switch is standardly installed on domestic installations for just that purpose. I understand that the MPPT controllers are suited to an input voltage that is near their max permissible, achieved by connecting the panels in Series. This also allows for smaller cable to be utilised. That's absolutely correct, Rusty
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Post by Deleted on Nov 28, 2016 15:33:27 GMT
I understand that the MPPT controllers are suited to an input voltage that is near their max permissible, achieved by connecting the panels in Series. This also allows for smaller cable to be utilised. That's absolutely correct, Rusty Why Thankyou ObiWan.
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Post by JohnV on Nov 28, 2016 17:11:45 GMT
Thank you for your input geo, but I am afraid it's too late.
4 x 260W panels and 40A MPPT controller purchased and collected last week, Majority of the wiring including completely rebuilding the low voltage distribution panel and fuseboard with heavier cables. panels wired series parallel with 2 pole rotary isolator in panel feeds. The only work remaining is constructing the unistrut frames (when the bits are delivered) and programming.
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Post by geo on Nov 28, 2016 17:46:33 GMT
Thank you for your input geo, but I am afraid it's too late. 4 x 260W panels and 40A MPPT controller purchased and collected last week, Majority of the wiring including completely rebuilding the low voltage distribution panel and fuseboard with heavier cables. panels wired series parallel with 2 pole rotary isolator in panel feeds. The only work remaining is constructing the unistrut frames (when the bits are delivered) and programming. You could still connect a couple of panels and try
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Post by peterboat on Nov 28, 2016 18:11:18 GMT
Ello Graham, you been causing trouble on the other channel? Anyway panels with bypass diodes should suffer less from shading problems, but the cheap second hand solar panels from solar farms may omit these. Doubt MPPTs would 'fight' each other but you could try setting them to slightly different charge voltages. I would love to meet this person called graham he has seemed to got you lot wound up. The name is Geo or Geoff not graham. I have seen the same effect with modern panels. As you say you could change the voltages on the controllers, but you still lose power when one cuts out, unless you have selected the panels so that they only supply a maximum current needed at the switch off point. If the panels sets between them are supplying the max current the battery will take at the switch off point you have lost the advantage the panels give free charge in part. Better I would suggest to use one controller and harvest all the power the battery will take. I am with you Geoff I have watched the video on U tube slight shading caused big drops on new panels they tested different brands and same result. I have 9 panels set out 3 in series x 3 and parallel back to the controller this works ok with the Midnite classic. When I had the 2 controllers I had 4 in series back to the controller x 2 and one panel for the starter all panels are 97 watt flexis quality made in the USA stuff bought cheap off ebay lol. I have been on solar for 12 years so everything is down to experience, I had panels before they were popular!!
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