Solar The Solar Panel Thread
- Thread starter cruza driver
- Start date
Not quite, each of these particlar panels is actually two sub-panels wired in series. Each sub-panel has a bypass diode across it. If a single cell is in shade, the output will be down to 50% for that panel. If the other two panels are still in sunlight, then 5 out of 6 sub-panels will be working, so output will be down by only 17%. for the system.
@Crusty181: The sub-panels will probably be made with the sub-panels split along the short edge or the long edge. In either case, it is likely from your photo that the A/C will only shade one of the sub-panels. So you should be down by only 17% if the A/C shades one of the panels.
cheers
Mike
Hi,
It is hard to seal the figure 8 cable coming out of the junction box. I don't know of a gland that would do this. If it was me I would be sourcing a couple of normal glands and splitting the figure 8 cable running each wire through a gland.
cheers
Mike
The shading is manageable, we free camp a lot and I can't recall too many times where we've enjoyed fun sun and I've not been able to orientate the van in our favour; conveniently with this problem panel location is we prefer the sun from over that side of the van anyway because it casts the shade on the preferable awning side.
The look of the distorted roof junction box with its misaligned lid may be disturbing, but inside it's polar white, clean as a whistle and with no evidence of ever having moisture in it. I presume that's the result of the panel physically sitting on it and having the full height of the 40mm panel frame protecting it. The roof junction doesn't box leak that's evident, so I'm in two minds whether to leave it and use to dual-core or replace the dual-core with solar cable. A downside to both, removing the dual-core means I break the effective seal but using the dual-core I suspect the MC4s won't seal effectively. I'll have a better look today, and roll the dice on that one then.
Hi @Clewsy , @mikerezny is right on the ball there. That is why the bypass diodes are in parallel with EVERY sub-panel. Hence the extra value of Schottky diodes in reducing voltage and current losses.
Hello again @Crusty181 , just having a bit of a look at your roof junction box. If the back of the panel was just resting on the top of that box, the heat from the back of the panel would stick things together pretty good. Try to avoid contact with back of panel to allow heat to be dispersed with good air flow.
Easier said than done I'm afraid. The rear panels location over the box is predetermined by the panels existing factory mounts, and short of moving the panel to the front of the van there's nowhere else for it to go. I can possibly lift the new panel a bit which may clear the box otherwise it would mean removing and replacing or relocating the box which I'm reluctant to do because it will create a potential leak point
Yes, possibly but again it mean stripping everything out and starting again. I have a better look tomorrow
Thanks @mikerezny makes sense. Although i thought the sub-panels were wired in parallel? Could be wrong.
@Crusty181 could you use a slightly higher aluminum bracket where the existing panel was, i custom one that bolts to existing one, ally strip. Bit more work with 2 lots of bolts but might give you the clearance over jbox.
@Crusty181 could you use a slightly higher aluminum bracket where the existing panel was, i custom one that bolts to existing one, ally strip. Bit more work with 2 lots of bolts but might give you the clearance over jbox.
What the heck is that site, you need to get away from your computer and get outside a bit more ...................... a proper LRPS (note capital letters) is need for those typical 5 days of cloud Victorian days....... Possibly a Jeep Thing
I looked at that, i can wrangle a slither of clearance doing nothing; maybe your idea to get another few mm. I have the cabling running thru suspended conduit between the panels to also take into account
Hi @Clewsy , further to your query regarding the shading of cells in a solar panel, I did comprehensive tests at home here in sunny Brisbane today. I have 3 different folding panels bought at different times. The first one is a 180 W folding panel with 72 groups of solar cells - 6 horizontal and 12 vertical in EACH portion. It has only two wires coming out of back of panel to connection box. OCV was 20.8 volts with both halves connected in parallel.. The next panel 200 W folding has 16 groups of solar cells - 4 horizontal and 4 vertical. It has 3 wires coming out the back and I have 2 Schottky diodes across both outputs. The output voltage of each sub panel was 9.0 volts, and connected in series provides 18 volts (OCV) at the terminals . The other half of this folding panel is the same and connected in parallel , so still only 18.0 volts OCV.
The last panel is 200 W with 32 groups of solar cells (4 horizontal and 8 vertical) with the same diodes and connections. OCV for each sub panel was 9.4 volts and when connected in series produced 18.8 volts OCV. The other half of the folding panel is connected in parallel with this sub panel giving me 18.8 volts OCV.
Just giving you some feed back on how heat affects panel voltage as you mentioned, the first panel was dropping very slowly as it heated up after about 15 minutes in the sun. The second panel was poor, dropping quickly from just over 18.0 volts to 17.8 volts in a few minutes. The last and more recent panel started at 18.8 volts and was fairly steady at this voltage even after 15 minutes in the warm sun. So yes, some panels do not do so well when they get hot - poor coefficient of heat resistance in solar cells.
As far as shading is concerned, the first panel would shut down if even partly shaded as only one panel in operation - no sub panels. The Schottky diode would however provide a path around the shaded panel for current generated by other panel/s in a series string. The last two folding panels each contain two sub panels with bypass diodes connected across output terminals. When I covered one half( vertically), the voltage in the unshaded sub panel remained at 9.0 or 9.4 volts, but the shaded panel voltage dropped to less than 6.0 volts in each case. However, the total of both sub panels was still around the 15.0 volt mark as they are connected in series. Even when I had shaded one complete panel (of the two folding panels) and half of the remaining one (which was connected in series) , a voltage of around 15.0 volts was still showing. I was not able to measure current as I had no connection to a controller or any load. However, I would think that the current output would then be only a quarter of total possible panel rating, but it would still be generating some power even at a lower voltage if bypass diodes are functioning properly.
I hope this helps one come to grips with these issues. It all depends on how the panel is set up (with or without sub panels) and the number of output leads coming out from the back of the panel/s.And the importance of bypass diodes cannot be underestimated!!
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Thanks @Boots in Action that's some great testing you've done there with different panels, well done.
I agree well worth testing to know the type of panel you have and how it's wired and if you have diodes or not can make a big difference if you can run your coffee machine in the morning or not.
I agree well worth testing to know the type of panel you have and how it's wired and if you have diodes or not can make a big difference if you can run your coffee machine in the morning or not.
There's a good example of why some people should restrict their travel videos to opinions about the beach views
Has anyone tried these flexible panels?
https://www.sunyee.com.au/collectio...ar-panel-generator-caravan-camping-power-mono
I wonder what they mean by “Do not wire the flexible solar panel in parallel or in series to avoid damage or shortened lifespan.”
https://www.sunyee.com.au/collectio...ar-panel-generator-caravan-camping-power-mono
I wonder what they mean by “Do not wire the flexible solar panel in parallel or in series to avoid damage or shortened lifespan.”