Arthur Brown Posted September 9, 2012 Share Posted September 9, 2012 Hi I have an 80wt panel on the roof and it normally generates around 21v before the controller. The other day whilst cleaning the roof I polished the solar with a wax polish. It looks nice but today, when the sun was shining I checked the output from it and it registered around 13v. Now in this weather I would have expected it to be around the 20-21v. The reason for the check was the fact that over the weekend the TV brought down the batteries (2) very quickly.. Today I have checked both batteries, put one on charge after bringing the water level up to scratch (no cell was devoid of liquid but all were low) It was showing a voltage reading of just over 11. The other battery was running 12.7v after a reasonable run but has now run the TV for four hours under test. My questions is this 1. Can the polish have any adverse effect on the solar efficiency? and if so what can I clean it with? 2 Will any of this battery problem cause a lesser reading from the solar on the imput side of the controller? I do realise I have a battery problem to sort but the low production from the panel does concern me. It is supposed to work from light getting more efficient with direct sunlight and I was getting as said above, 21v in normal british sunlight. Your comments would be appreciated. Art Link to comment Share on other sites More sharing options...
Bolly1965 Posted September 9, 2012 Share Posted September 9, 2012 I'm by no means an expert but polish makes it shiny and shiny means light is being reflected back, so some of the light may not get through to the cells. Polish make contain UV filters, while this may have an impact I wouldn't have thought it would have been so drastic Link to comment Share on other sites More sharing options...
coach2000 Posted September 9, 2012 Share Posted September 9, 2012 I read somewhere recently that it is not advisable to ue polish on Solar panels, sorry cannot remember where. As you say it would make it shiny and possibly reduce the rays needed to make the panel work. Use some caravan cleaner to get it off and then rinse off or use a rubber blade. Clive. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 10, 2012 Share Posted September 10, 2012 Art I don'r believe applying wax polish to a solar panel will reduce its efficiency because it might make the panel more reflective, but I can imagine that the thin layer of polish added to the panel's upper surface might reduce its output by acting as a barrier. There's a lot of on-line stuff about cleaning solar panels (example here) http://www.yougen.co.uk/blog-entry/1786/Do+I+need+to+clean+my+solar+panels+to+maintain+efficiency'3F/ Received wisdom seems to be to just use water and a soft brush/cloth every now and again, with a mild washing-up-liquid solution being employed if the panel is really grimy. Panels on sloping house roofs will tend to self-clean of course, so horizontal panels on motorhome roofs may benefit from more regular attention. I can't find anything about the effect (good or bad) of polishing a panel, possibly because it's unlikely that domestic panels would be treated like that, and/or that owners of leisure-vehicles (boats, motorhomes, etc.) either have never done it because they were wary of the procedure or, if they have done it, have not noticed any positive/negative effect. It's a pity you did not check the panel's output before the polishing exercise, as you'd then have before and after figures that might confirm whether or not the polishing reduced the panel's efficiency. When the panel's output was registering 13V you guesstimated that it should have been 20V-21V but, if there's a problem with your system, 13V might have been the panel's output prior to polishing. I suggest you re-check the ouput when the panel is in strong sunlight and, if you decide that the ouput is down on what you'd expect, remove the polish and see what happens. Not sure what would be best to remove wax polish with minimum risk of harming the panel. You could try a vinegar or washing-up-liquid solution or (as Clive recommends) a caravan cleaning product. I imagine that motorhome owners who clean the roofs of solar panel-equipped vehicles don't take ultra-special measures when washing the panel (and I'm certain that dealership staff aren't high on TLC when cleaning roofs), so panels must be reasonably tough. Can't see why having a heavily discharged battery should affect the output reading of your panel. But I've no hands-on experience to support that view - it just seems unlikely. Presumably you had your two batteries connected in parallel when you read the 13V ouput figure. Try operating the system with the 'good' (12.7V) battery on its own, then with the 'bad' (originally 11V, now under charge) on its own, then with both batteries connected together, and see what output readings you get from the panel. You haven't said how old your batteries are (8 years?), but the combination of one battery at 11V and the other at 12.7V suggests that the former will need replacement. If that proves to be the case, then combining a new battery with an elderly one is not recommended. Link to comment Share on other sites More sharing options...
Brambles Posted September 10, 2012 Share Posted September 10, 2012 One issue I can see with polishing a panel, and not sure how relevant it would be, is the generation of static electricity while polishing. If using a dry synthetic duster I can imagine very high voltages will be generated on the surface of the glass, creating a very high voltage field across the cells. This could have damaging implications for the solar cells. I think I would refrain from applying any polish which is not applied wet and wiped off wet or polished using a damp cotton cloth. Food for thought maybe! The extra reflection from a highly polished surface is very small but will reduce the light transmitted by a small percentage but counter balanced by a cleaner panel with less dirt sticking to it to block light. Link to comment Share on other sites More sharing options...
roger s Posted September 10, 2012 Share Posted September 10, 2012 Interesting post Arthur, as I had suspected our 85w panel was not outputting out what I expect(18/21v) on a sunny day and checked its output to the regulator and this was only showing 12.8/13v and I havnt touched the panel with polish or anything else for a few weeks being on a longish UK trip. I have monitored the output from the regulator to the battery which is also low and the leisure battery voltage on and off load and the panel is certainly charging the leisure battery so will have a proper look when I get home Link to comment Share on other sites More sharing options...
hallii Posted September 10, 2012 Share Posted September 10, 2012 Under load surely the voltage would "sag" at the output of the PVP? The only way to see what voltage is generated is to test open circuit, and that will vary with time of the day, sun angle, atmospheric haze, temperature of the panel and so on. To make a meaningful measurement would need some sophisticated equipment. Two duff batteries (and that is what they are judging by the voltages) will load the regulator and so the PVC the voltage only rising as the batteries approach full charge. Typically a fully charged a battery would read 12.7 V or so, a bit more for a gel. The panel voltage can rise to 14.4V when the batteries are charged and the sun is shining. H Link to comment Share on other sites More sharing options...
Arthur Brown Posted September 10, 2012 Author Share Posted September 10, 2012 First, thank you all for your replies. I have noted your comments. I have now confirmed that one battery is on its way to the graveyard for batteries. The other is standing well. I have now put it on charge to make it fully charged and will record that level a couple of hours after taking it off charge. The solar panel will get a clean to remove any possible UV filter and a check on output will then be made. I will update as information is gained. Many thanks Art Link to comment Share on other sites More sharing options...
bazooka Posted September 12, 2012 Share Posted September 12, 2012 The instructions with my solar panel state use just clean water. Baz Link to comment Share on other sites More sharing options...
Irina Postelnicu Posted March 1, 2018 Share Posted March 1, 2018 I read recently this post https://www.greenmatch.co.uk/blog/2016/04/cleaning-and-maintenance-tips-for-solar-panels In it it gives general tips with how to improve the solar panel output. What it specifies about cleaning it is that you can use a gentle detergent but many times you don't need to even clean it. Maybe you can find some more helpful information in there. Otherwise, I hope you solved your problem! Irina Link to comment Share on other sites More sharing options...
aandncaravan Posted March 1, 2018 Share Posted March 1, 2018 I agree with Hallii, that your 'expected' 21v is open circuit and off load. Under the load of a duff battery the voltage from the Solar Panel will drop substantially, possibly even below 12v on a none MPPT Solar reglulator. I would suggest that if you remove the duff battery and connect back in the 12.7v battery, by mid day tomorrow you should see a healthy 14v, or whatever is the max output for your Solar regulator, and a Solar Panel output closer to 19v. You probably won't see more than 20v without isolating the panel from the regulator as the 21v is usually an open circuit rating? Don't forget that when you replace the duff battery with a new one, the older 12.7v battery should be no more than 6 - 12 months old. Ideally, all batteries connected together should be the same age, make, model, technology and size. . Link to comment Share on other sites More sharing options...
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