spospe Posted January 3, 2011 Share Posted January 3, 2011 Three years of using a 65-watt solar panel The following information has been gleaned from our Kyocera 65-watt solar panel, mounted on our MK7 Transit based Autosleeper Duetto. It is offered to Forum members on the basis that questions are often raised about solar panels, but little hard data has ever been offered before as to what you can actually get from them in practice. To apply these data to your own panels, multiply the figures by the ratio of our 65-watt panel to the size of your panel; so for example if you have an 85-watt panel, multiply by 1.3 and for a 135 watt, by 2.1 Different methods of panel construction do give different efficiencies, but I do not think that the differences exceed 10% or so. Our panel is mounted horizontally on the roof of the Duetto and does get some shading from roof lights when the sun is very low, but by that time the panel output is low and I do not think it makes any real difference to the results. All figures quoted below have been measured in situ. A 65-watt panel will give about 5.4 amps maximum output at 14.7 volts maximum voltage into the battery. 1) The rated power output of a panel is its normal maximum and this will only be approached over about a 4-hour time span (2 hours before and after the solar noon) with the sun shining directly onto it. Any shadows will have a dramatic effect. Forget clear blue sky, the maximum output we have ever seen from a brilliant clear blue sky has been 0.4 amps at noon and usually only a half of that (this happens when parked in the shadow of something which covers the panel). 2) Location does not make too much difference, but height above sea level and time of the year can have a big effect. At the North Cape of Norway (1000 ft), the noon value in mid-June was 3.2 amps (2.8 at sea level) and at St. Remy de Provence in France also in mid-June (300 ft), the noon value was no more than 3.5 amps. One major difference between the North Cape and St Remy was temperature, the Cape was around 0 degrees centigrade and St Remy was 33-34 degrees centigrade. In 2010, we stopped at the top of the Col d’Aubisque (5611 ft) and recorded a value of 6.4 amps at the solar noon; this value was greater than the maximum rated output of the panel (5.4 amps). At home, near Stockport around Midwinter’s Day, the maximum output was 0.7 amps at the solar noon and effectively over the (short) day the maximum power was no more than about 2½ ampere-hours. Remember, this was a maximum figure; with cloudy weather the figure would have been less than 1 ampere-hour. 3) The above readings are perhaps interesting, but not too much value in determining what you are likely to get out of a panel over a year’s use; for that the total cumulative figure is required and for our panel that figure is 1.7-kilo ampere-hours per year. Given that the Duetto has a 90 ampere-hour leisure battery and that batteries are typically about 70% efficient, the solar panel’s output has been sufficient to recharge the battery 14½ times over the course of an average year. We use our Duetto for about 4½ months a year, made up of two months between mid-May and mid-July and two months from early September to early November, with the remainder spread over the rest of the year. 4) One conclusion we have come to, is that fitting an extra battery is a more cost-effective solution to the power problem that is fitting a solar panel. This is especially true if the weather is bad and / or you are using the Motorhome at either end of the year when the intensity and duration of sunlight is quite low. Our results have not varied much from year to year and it seems that the low sun of Norway has been compensated for by the 24 hours of daylight there and the more southerly latitudes of France have had their greater sun strength benefit reduced, by both higher temperature and shorter day length. I hope that the above is of some use / help to you all and my apologies in advance for the somewhat ‘stuffed with numbers’ approach to presenting the data. The key figure is the 1.7-kilo ampere-hours for our 65-watt panel; you will be doing remarkably well to beat this rate over 12 months. Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 3, 2011 Share Posted January 3, 2011 Excellent post, Michael. Thank you.One question. If you added a battery in lieu of a solar panel (on the assumption the existing battery has largely been charged from the solar panel) how would you then charge the batteries?If you double the battery capacity I assume you are anticipating fairly heavy discharge in the absence of the solar panel, all of which would have to be made good from alternator or mains. Other things being equal, will you not have to drive (as you have a solar panel, I assume you don't use hook-up), for twice as long between stops, to put back what you will be taking out? Could you realistically achieve this? Would you not then need a B2B charger to compensate? Link to comment Share on other sites More sharing options...
spospe Posted January 3, 2011 Author Share Posted January 3, 2011 Brian Kirby - 2011-01-03 4:03 PMOne question. If you added a battery in lieu of a solar panel (on the assumption the existing battery has largely been charged from the solar panel) how would you then charge the batteries?If you double the battery capacity I assume you are anticipating fairly heavy discharge in the absence of the solar panel, all of which would have to be made good from alternator or mains. Other things being equal, will you not have to drive (as you have a solar panel, I assume you don't use hook-up), for twice as long between stops, to put back what you will be taking out? Could you realistically achieve this? Would you not then need a B2B charger to compensate?BrianDoubling the battery capacity does not automatically mean having to drive twice as long in order to recharge said batteries. The vehicle alternator will do a pretty good job of charging two leisure batteries in about the same time as just the one. Our Transit alternator has a maximum output of 95 amps (if I am reading the label correctly) and an extra battery will not present much of a challenge to it.You are correct in that we do not use hook-up unless it is included in the cost of the site and not always even then. If for example it is cold, raining and blowing a gale, the thought of getting the lead out and later putting it away, is rather off-putting.We are not heavy users of power (no TV), but when we find a place we like, we will stay for quite long time periods without wanting to drive anywhere and that is where the solar panel is useful. In these cases, we could get the same effect with an extra battery at much less cost than a solar panel installation.Something that I omitted from the original post; fit the largest panel you can get on your roof. If you can fit a 135-watt unit, never, ever think about an 85-watt!Do we like our panel and would we do it again? Yes; but it's good to know the truth rather than live in a world of wishful thinking ;-) Link to comment Share on other sites More sharing options...
Paul- Posted January 3, 2011 Share Posted January 3, 2011 Your solar panel is one of the better ones, but don't say what make or type of charge controller you're using & where its positioned, as the panel is fitted horizontally if you're using a mttp controller ;-) Paul Link to comment Share on other sites More sharing options...
Travelling Tyke Posted January 3, 2011 Share Posted January 3, 2011 Many, many thanks for this SPOSPE! This is the info I have been waiting for. Reliable, unbiased figures have been difficult to obtain when I have asked about real in-situ performance of these panels. Being a Tyke I am adverse to spending my hard earned cash unless there is a real benefit to be gained. I have been temped, but the fact that my two leisure batteries have done their job over our New Year breaks (Off HU) using TV and DVDs, lights, etc have made me reticent in the past. Your posting has confirmed my thoughts that for me a solar panel is not required! One point I should make tho, I have replaced all of the habitation lights with LEDs, which has reduced the power taken from the batteries. Once again, thank you. Link to comment Share on other sites More sharing options...
747 Posted January 3, 2011 Share Posted January 3, 2011 Thanks for the interesting info. I have a free standing 90 watt solar panel (yes I know, I should have bought a caravan ;-) ). I did a little experiment in October. I laid the panel flat and measured the amps from the panel. I then pointed it towards the sun and increased the output by just under 50%. This was late afternoon with a clear sky. My panel was not a cheapie off ebay and I believe that there will be a difference in output between panels, although many users say that they all come from China and are all the same. As soon as I get a decent day, I intend to connect mine directly to the Electrobloc and I will be able to monitor performance from my control panel. This will also apply to my wind charger as I can have either one (or both) connected. Link to comment Share on other sites More sharing options...
spospe Posted January 3, 2011 Author Share Posted January 3, 2011 Paul- and Tyke Our controller is a Steca PR1010 (sorry, I should have mentioned this in my first post). The Steca gives considerable usage information, such as voltages and ampere-hours of charge. It is fitted about 2 cable metres away from the panel and about the same again from the battery. The cable used for connection is about double that specified for the current involved and is 2.5mm cross sectional area (I wanted to be sure that volt drops were minimised). A further point to mention is that in January's MMM on page 169 a Steca controller is shown and it is set-up wrongly! In the article, "Light of my Life" the author Michael Thomas describes his solar panel installation and shows a Steca PR1010 configured for installation as a battery condition monitor. This will only work properly if the van load is connected to the output terminals of the regulator (last two terminals on the right) and as can be clearly seen in the photograph, they are not. In his case, the regulator must be set up to measure battery voltage and not condition / usage as shown. Link to comment Share on other sites More sharing options...
spospe Posted January 3, 2011 Author Share Posted January 3, 2011 747 See the article in January MMM on page 169, where this point about angling the panel is mentioned. Link to comment Share on other sites More sharing options...
747 Posted January 3, 2011 Share Posted January 3, 2011 spospe - 2011-01-03 7:31 PM 747 See the article in January MMM on page 169, where this point about angling the panel is mentioned. Thanks, I will do. WHEN IT EVENTUALLY ARRIVES. >:-) :D Link to comment Share on other sites More sharing options...
dipsticks Posted January 4, 2011 Share Posted January 4, 2011 Thanks all very interesting posts. We have a Duetto and like to be off hook-up on quieter sites whenever possible. Initially we fitted a second battery to double the capacity to 180ah, then we fitted an 85 watt Kyocera solar panel flat on the roof and connected it to the batteries via a Morningstar regulator. We mounted the regulator adjacent to the battery under the passenger seat, in order for it to be in same temperature environment as the battery. The regulator applies around 14.6 volts or more to the batteries in full sun when the battery temperature is around 20 degrees C and thus charges well up to the gassing level. This achieves 100% charge and it is therefore neccessary to keep a close eye on the elctrolyte levels on flooded batteries. The second battery of our AS Ford Duetto is not really a dedicated leisure battery and is used by the vehicle electrical system too, when the engine is running. We couldn't understand why the batteries actually discharged when the engine was started. Finally the penny dropped when an expert on another forum explained that since the vehicle electrics considered that the auxilliary battery(ies) were overcharged it then discharges them or balances the charge into the engine starter battery. We have never run short of battery power since the modifications and have used the Eberspacher heater (power hungry on start up) on several trips early and late season. Happy New Year Peter D Link to comment Share on other sites More sharing options...
Paul- Posted January 4, 2011 Share Posted January 4, 2011 Thanks for info on the regulator, I have two leisure battery's with a free standing solar panel set up for each, I have a steca on one & a morningstar on the other, I've found that the morningstar gives me the best readings I've never had a problem regarding power & my daughters likes to watch telly a lot but if the need did arise in the darker months I would be able to put all the panels onto one battery. Link to comment Share on other sites More sharing options...
lennyhb Posted January 4, 2011 Share Posted January 4, 2011 Thanks for the info Michael. Just finished fitting my panel at the weekend finished too late on Sunday to get any reading off it. Yesterday was very dark & overcast I was getting only 150ma a bit disappointing. Today was a different story sill overcast but much brighter took some readings between 12:30 - 13:00 results were between 0.5 - 0.7 amps then the sun tried to show it's self through the clouds still light cloud obscuring the sun but readings increased to 0.9 - 1.1 amps, then noticed from an upstairs window the panel had water droplets on it from a shower last night. Got the ladder out and dried it off, readings increased to 1.3 amps 20-30 % increase because of a few drops of water. I noticed by 14:30 output was dropping off fast 0.5 amp and the sky still looking fairly bright. Leisure batteries are 2 x 80ah gel, voltage readings yesterday were 12.7v on the leisure batteries & 12.8v on the starter battery by 13:00 today both batteries reading 13.0v. The panel is an 80 watt Monocrystalline unbranded from ebay (£160), solar regulator is a Schaudt as I have an Elektroblock expensive but makes connections easy and charges both leisure & starter batteries. After a disappointing start yesterday I am well pleased with today's results considering the time of year & how cloudy it has been. Link to comment Share on other sites More sharing options...
spospe Posted January 4, 2011 Author Share Posted January 4, 2011 Dipsticks I am curious as to how you got an 85-watt panel to fit the roof of your Duetto. When we were getting our van built, the largest we could get to fit without overhanging anything was a 65-watt unit (the 85-watt would have been our choice, but there was not enough room). What make is your panel? Ours is a Kyocera. Link to comment Share on other sites More sharing options...
dipsticks Posted January 4, 2011 Share Posted January 4, 2011 Ours is a Kyocera (think I mentioned it) Model KC85GX-2P 1007x652mm. It only just fits without any overhang but we are totally free of any more real estate on the roof now. Ours is a Mk7 too but I have noticed some different arrangements of vents aerials etc on Duettos around our era (July 2007 build), Maybe it depends which fitter assembled them at AS. The panel just fits on the rear offside corner of the van with the 1007 dimension set accross the vehicle and the 652 running front to rear. I used 4.0mm cable, quite a tortuous route to the base of the passenger seat ! Link to comment Share on other sites More sharing options...
spospe Posted January 4, 2011 Author Share Posted January 4, 2011 Thanks dipsticks, the photo was a nice touch. I am not 100% sure, but your roof does look a little different to ours and that probably explains how you managed to get an 85-watt panel on it. I am jealous ;-) Link to comment Share on other sites More sharing options...
747 Posted January 5, 2011 Share Posted January 5, 2011 I met the author of the MMM piece on solar panels. It was near Fraserburgh last September and he had just pulled up. I had been on the point of moving my van to a better place to set up my wind turbine when he and his wife arrived. I thought I had better explain why I would be moving nearer and he told me of his poorly performing wind turbine and he had given up as it was hopeless. At that point, I felt it would be ungracious to set up my 5 metre mast and guy ropes. It was a pity because I would have got a decent output given the conditions. :$ He has written an excellent article and it was very informative. There is only one small point that I did not agree with. He suggests a minimum of a 13.3 amp regulator for 2 x 80 watt solar panels. I currently use a 7.5 amp regulator and according to the paperwork, it is capable of supporting an 80 watt wind turbine and a 100 watt solar panel. I hope so, because I have wired them up so that I can use both at the same time (I have a 90 watt panel). Link to comment Share on other sites More sharing options...
colin Posted January 5, 2011 Share Posted January 5, 2011 Have used solar panel for 10years and in conjunction with electric fridge is very good. Link to comment Share on other sites More sharing options...
747 Posted January 5, 2011 Share Posted January 5, 2011 Could you expand on that a bit please Colin? Link to comment Share on other sites More sharing options...
colin Posted January 5, 2011 Share Posted January 5, 2011 Ok I have a semi flexible panel of 30w nominal output (more on that later) which is conected to a single (small size) elecsol battery. The main power usage is a 12v fridge, we watch very little tv and have flouresent lamps. The battery is largest that will fit under a VW seat and I would not want to use up any other storage space on batteries. This set up will keep going for several days with no other input, but we turn off fridge at night as gf doesn't like noise, so have fitted extra insulation to fridge, and the fridge is a 'chest' type which losses less when open. Generaly the warmer and brighter it is the harder the fridge works and the more output from the panel, so they work well together. For many years the van was used daily, but for the last couple of years it has been 'off road' and only started occasionaly to be driven around farm, it has a link cable with mechanical heavy duty switch so the leisure battery and vehicle battery can be connected together, so no flat batteries even if left for months. I am not too interested on figures, as long as set up does the job, but did test output of panel when first fitted and got close to 5amp output on a sunny mid day in bedfordshire which would indicate that the quoted nominal output is a conservative figure. Link to comment Share on other sites More sharing options...
Travelling Tyke Posted January 5, 2011 Share Posted January 5, 2011 Sounds like you have a good system there Colin. 5 amp at 12 Volts (= 60Watt) from a 30watt system? recon you miss-typed/miss-read there... If not I'd like one please...... :-D Link to comment Share on other sites More sharing options...
colin Posted January 6, 2011 Share Posted January 6, 2011 Travelling Tyke - 2011-01-05 10:54 PM Sounds like you have a good system there Colin. 5 amp at 12 Volts (= 60Watt) from a 30watt system? recon you miss-typed/miss-read there... If not I'd like one please...... :-D Yes that would be good :D Should read 2.5amp Link to comment Share on other sites More sharing options...
spospe Posted August 2, 2013 Author Share Posted August 2, 2013 I am resurrecting this old thread so as to bring it up to date; it should now read "Six years with a solar panel" The following is my personal experience and is being offered as a guide to fellow Forum readers. 1) fit the largest solar panel(s) that you can get on the roof. 2) Direct sunlight falling shadow-free onto the panel is necessary for a decent output. If the panel can see clear blue sky, but is in shade (say from a wall), the output will only be 10% of that when the sun is directly on it. 3) Any shade will have a dramatic effect on output. The shadow of a small branch can drop the output up to 50% (or more depending on the time of day and the size of the shadow). 4) If you love Spain and seek a nice shady pitch, or one with a sunshade you can kiss goodbye to most of your panel's output. 5) Mount your panel as high up on the roof as possible, because shadows from roof lights / aerials etc. will have the same affect as branches, especially at either end of the day when the sun is low. 6) Wire the output of the panel directly to the leisure battery terminals and use the large diameter cable. DO NOT tap into existing wiring as this will lead to false readings which can affect the functioning of the solar panel regulator. 7) If using a Steca solar regulator, be aware that these work on both 12 and 24 volt systems and this can lead to the regulator setting itself to 24 volts and frying the battery if attention is not paid to 6) above. 8) Make sure that the installation of the panel includes readily accessible fuses for both safety and testing purposes. 9) Do not expect much from the panel in the two and a half - three hours either side of sunrise / sunset. 10) Consider a free standing panel. They mean that your van can shelter from the sun and you can get the full benefit of the sun on the panel. 11) Winter use in the UK means virtually nothing useful from a panel; they will keep your batteries in good shape when parked-up, but not provide much useful power output. 12) Any snow on a panel will kill the output. Dirt itself does not seem to have much of an impact on output, but leaves do. Ice and rain have little effect. That's it for now, enjoy your summer travels, wherever you roam. .......... Michael Link to comment Share on other sites More sharing options...
spospe Posted August 3, 2013 Author Share Posted August 3, 2013 One last point, which occurred to me after posting and that is the effect of stopping under an electric street light. On two occasions we have parked under a light, once at Hamlin and once at Forges les Eaux and both times the panel continued to produce (not much) power for as long as the lights were on. The output is very small, of the order of about 30m/a and you have to be directly under the light and the lamp has to be of a 'white' colour (not one of those yellow, sodium types). Mentioned out of interest, it's not a factor to influence where you park for the night as the total nightly gain must be under a quarter of an ampere hour. Link to comment Share on other sites More sharing options...
spospe Posted August 5, 2013 Author Share Posted August 5, 2013 Has no one any comments to add? I really thought that there might be some interesting personal experiences to be shared on this subject and that we could all learn a bit. Are you all on holiday? Link to comment Share on other sites More sharing options...
malc d Posted August 5, 2013 Share Posted August 5, 2013 spospe - 2013-08-05 12:28 PM Has no one any comments to add? I really thought that there might be some interesting personal experiences to be shared on this subject and that we could all learn a bit. Are you all on holiday? I think your very informative post has been so comprehensive that others may not have much to add. For those, like myself, who don't use a solar panel, it can be useful info. So thanks for taking the trouble to post it. :-| Link to comment Share on other sites More sharing options...
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