In this post I am doing a follow-up after using the panels for almost 7 months and discuss some tips and trick on the wiring side. I will add some photos to show how the sealant is holding up in the next update.
I ended up with the 2 parallel arrays containing 5 panels each in series. This was hooked to an Outback FlexMax 80 Solar Controller feeding an 800 Ah LiFePo4 battery bank. The bank is set up to deliver 12 to 14V. We are currently running 2 Intel Quad Core I7 laptops, a 12Volt 258 liter double door compressor fridge/freezer, one 5kW and one 3kW diesel heater and the usual small 240V electric equipment via a 1500Watt inverter.
We also use the inverter to power a single 1200Watt Infra-red hot plate for cooking.
We have been getting a charge of roughly 1.8kW to 4.0kW during summer. It took some doing to get the FlexMax set to its optimal performance for this configuration.
Later, as winter was approaching, power dropped dramatically to between 1kW and 1.8kW per day depending on the weather.
Currently it is close to mid winter and charging is between 0.4 and 1.4kW mostly but some days as low as 0.1kW.
Due to the winter rain season, we get very little sun if any for a few days on end. The power is still keeping up with our usage although we take care not to waste power.
Issues that surfaced to date:
When we had the bus converted, the bus builder skimped on the wire sizing which was OK for the old array but the wire sizing should have matched the controller maximum rating. After installing the new Solar array, I found the wire from the controller to the battery getting very hot when output amps exceeded 30A. On a good sunny day, I saw moments of charge exceeding 50A. The wire got so hot you couldn’t touch it.
As an interim safeguard, I set the controller to limit output to 30A max. This is running the wire at luke warm temp on sunny days. I am planning to upgrade the wiring to the correct spec soon.
Solar panels and wood burners
We are using a “Little Cracker” wood burner with a heat powered stove fan during the cold winter months. One day I got onto the roof to inspect the panels and found that there is quite a layer of black soot on some panels and realized that it must be from the wood burner chimney. There was no harm done to the panels but it will need cleaning on a fortnightly interval, depending on burner usage. The soot is easily removed with a damp cloth. Light soap can be applied if needed.
Solar Panel MC4 Connector Review
At 7 months in the New Zealand sun, I found the connectors starting to look a little dull and the surfaces seem to lose their smoothness – typical harsh sun corrosion on the connector bodies. To fix the problem, I took some rubber roof coating and painted the connectors. That will keep any UV away for as long as the roof paint lasts – which have lasted 10 years before I did a re-coat. Esthetically it is much better because you hardly notice the lumpy connectors after the color match.
Discoloring sealant/Quick dry silicone sealant drama
During the inspection, I noticed that the clear sealant I used to affix the panels, is turning dull white. This does not seem to impair the sealant properties. The panels are all still tight on the roof and the sealant seems to be holding perfectly to the panels and roof coating.
I have assisted another full time RVer to fit a 9 panel array to his roof. He used the “quick dry” silicone at first but found that it caused a mess as it left him no time to smooth it out properly before starting to form a skin. So, if you plan to use the silicone method, go for the standard or slow setting silicone.