Berniea Posted July 31, 2019 Share Posted July 31, 2019 I have 2 x 150w solar panels fitted to my van - They were fitted when I bought the van and I believe they are almost 6 years old. I now have a the ability to see what the panels are producing in terms of watts and amps through a Victron 30 amp MPPT controller and today at midday (not a cloud in the sky) the output was just 120w. Both panels are producing around 21 volts. Is it normal to "lose" 60ish% ? Link to comment Share on other sites More sharing options...
spirou Posted July 31, 2019 Share Posted July 31, 2019 I'd have to check but the most I've ever gotten out of my 120W panel (and victron controller) flat on the roof was one winter day in Romanian mountains and it was 112W if memory serves. On a "normal" summer day it might hit 90W, but usually the battery is full before mid day and the maximum would be in more like 60-80W range. If you really want to test it then drain the battery quite low, cover the panel/remove fuse until mid day and see what happens. Link to comment Share on other sites More sharing options...
BruceM Posted July 31, 2019 Share Posted July 31, 2019 Good advice from spirou. Your solar regulator will only output power if it’s needed. For instance with full batteries my regulator output is minimal. Then as I start turning electric devices on (wifi, laptop charger, lights, heating etc) I can see the output from the solar rise to meet the load. Link to comment Share on other sites More sharing options...
Berniea Posted July 31, 2019 Author Share Posted July 31, 2019 Ah thanks both. Your explanations makes perfect sense. When I checked I wasn't on hook up and the batteries were indicating a charge of 13.1 volts (full?). I only switched on a couple of things i.e. lights, inverter and TV, just to check the draw in amps. From what you are saying I need to deplete the batteries a bit and then see what the solar panels are producing in full sun. Link to comment Share on other sites More sharing options...
StuartO Posted August 1, 2019 Share Posted August 1, 2019 Berniea - 2019-07-31 10:25 PM Ah thanks both. Your explanations makes perfect sense. When I checked I wasn't on hook up and the batteries were indicating a charge of 13.1 volts (full?). I only switched on a couple of things i.e. lights, inverter and TV, just to check the draw in amps. From what you are saying I need to deplete the batteries a bit and then see what the solar panels are producing in full sun. No, all you need to do is apply a bigger load, so switch all your habitation lights on, TV, radio and anything else you have, then see how much your solar panels are generating. Link to comment Share on other sites More sharing options...
spirou Posted August 1, 2019 Share Posted August 1, 2019 That might not do the trick with some regulators as they might not switch back from float to bulk phase. Or the total load doesn't even cover whatever the panels produce. With LED lights and other small loads it's not that easy to stress 300W panels. Link to comment Share on other sites More sharing options...
StuartO Posted August 1, 2019 Share Posted August 1, 2019 spirou - 2019-08-01 11:48 AM That might not do the trick with some regulators as they might not switch back from float to bulk phase. Or the total load doesn't even cover whatever the panels produce. With LED lights and other small loads it's not that easy to stress 300W panels. I agree but if you've switched everything on and the solar panels are carrying the load do you really need to know any more? Link to comment Share on other sites More sharing options...
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