MK111 Rear Hatch Solar Panels 300W

[Patrol Dude]

Hey mate, I suspect it would be OK. It's sole purpose is to get the heat away from the rear of the panel, obviously the thicker the better. But space is a issue with the room that we have on the rear hatch. I was able to get the 8mm polycarbonate sheet to fit with a little massaging, I suspect that the corflute would fit with next to no massaging which would be a great outcome [emoji106]
Good luck. Cheers


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Patrol Dude
4.2TD

[Phil G]

Parts used:   Multi wall Polycarbonate Sheet 8mm thick. This is to keep the heat of the solar panels off the hatch. At 8mm thick this gives a real robust base, with excellent cooling properties.

Jeff,
I'm not sure where you heard that these Sunlite polycarbonate sheets had "excellent cooling properties".    They actually have high thermal insulation which means they do not conduct heat at all well.  They are designed to keep heat out.  If you mount them under a panel, the panel will overheat the the same as happened to mine.  Hate to see any of yours suffer the same fate.  I'd suggest an airgap behind the panel is the best way to prevent them overheating.
Cheers
Phil

[Patrol Dude]

Hi Phil, from my research on many caravan forums and reading why solar panels die is because as you indicated the panel over heats. The overwhelming response to this is that when a air barrier is placed under the panels this allows the heat transference to the air gaps in the sheeting. This heat then has the ability to disperse more readily than if the panel was directly mounted to the surface. The great benefit of the Tvan rear hatch is that it has large areas built into the hatch design where the air flow and heat can exit from.

The guys that use the polycarbonate sheets have all had a positive experience with there panels as far as I could ascertain. Hence my decision to "give it ago".

As mentioned in the above thread, these polycarbonate sheets are not the only option and I suspect a lot of people will try a lot of different materials to try and aliviate this over heating issue.

The most important thing I think is to mount the panels on a platform that is easily removable, that in the event a panel does die it's easy to replace - which I have done[emoji6]
Cheers


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Patrol Dude
4.2TD

[Graham Norfolk]

Hi Jeff,
Just a observation, with the two 80w panels on my hatch and the shower tent usually attached to the tent that goes into the hatch I had my struts increased by 'Struts Australia' to 670N. This seems to be adequate as we need to physically pull the hatch down partly to deploy or put away the tent. So far the panels seem to be working well after two winters of trials including 8 days volunteering at the BRB with the 80 ltr fridge and lights operating only on the panels and the T-van 120 ah battery.
What sort of damage does the heat do to the panels, do they buckle, break or discolor, I'm interested as would hate to be stuck out there with no panels. I do have a alternative with the auxiliary battery on the Nissan but hope it doesn't come to that.
Your set up certainly looks good, did you utilise the 50w panel on the T-van as well?
Cheers
Graham

[Patrol Dude]

Hi Graham, from what I've read the solar panels just die - no more output! Had a 100W flexipanel on my patrol do just that as well. Worked great then nothing!! Had that replaced under warranty though.

Yes the 50W original panel is still in place doing its thing[emoji106]

I would Recommend that you place a multi meter across your panels a couple of times a year just to check the output.

Cheers


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Patrol Dude
4.2TD

[Phil G]

The overwhelming response to this is that when a air barrier is placed under the panels this allows the heat transference to the air gaps in the sheeting. This heat then has the ability to disperse more readily than if the panel was directly mounted to the surface. The great benefit of the Tvan rear hatch is that it has large areas built into the hatch design where the air flow and heat can exit from.
The guys that use the polycarbonate sheets have all had a positive experience with there panels as far as I could ascertain. Hence my decision to "give it ago".

Gday Jeff,
Just spent considerable time searching Caravaners Forum on Flexible Panels.  A lot of people there with failed flexible panels - like I experienced.  People were experimenting with corflute and lexan sheets under the panels as a solution but they are misguided.  These materials are insulators, not conductors. They will make the solar panels hotter (like my sheet of 3mm ply did) because they do not conduct heat away from panels.  The lightweight flexible panels need the airgap for active air flow behind the panel - so do the glass panels for that matter!  But having lost considerable money on a flexible panel ( mine lasted 8 months) I'm sticking with glass.
My flexible panel died over a couple of days.  It started to underperform (output less than 1 amp despite full sunlight and discharged battery).  Then after another day, no output at all.  The panel had been too hot to touch.   Still had voltage at the leads but no output.  Bypassed the regulator and still zero output.  Tested it all back home and the panel was dead.

[Cruiser 105Tvan]

Might be good to get hold of Boobook and see how long his panels last.

[Graham Norfolk]

I have a similar set up to Boobooks infact he guided me through setting it up. With out jinxing my panels they have lasted two winters maybe they are getting enough air under them with the velcro attached?
Cheers

[Patrol Dude]

Gday Jeff,
Just spent considerable time searching Caravaners Forum on Flexible Panels.  A lot of people there with failed flexible panels - like I experienced.  People were experimenting with corflute and lexan sheets under the panels as a solution but they are misguided.  These materials are insulators, not conductors. They will make the solar panels hotter (like my sheet of 3mm ply did) because they do not conduct heat away from panels.  The lightweight flexible panels need the airgap for active air flow behind the panel

Hi mate, agree to a point - considered all your points prior to going down the polycarbonate sheet road. My reasoning is if you want to mount the sheets permanently then you have to attach them to something. So what do you attach them to? The panels going to get hot regardless of what they are connected to. The fibre glass is at least 5-10mm thick and once the heat transference has heated up the fibre glass it's going to take a lot more to cool it down, with the added challenge that once the fibre glass gets hot, the interior of the Tvan is also hotter! I only wanted the panels in the sun when we where actually stopped and set up for camping to try and prolong the life of the panels, hence placing them on the rear hatch. Also, it's a set and forget set up, nice and quick [emoji106] And they are very hard to steal either behind the deck, or when they are set up, additional bonus points [emoji106] Plus with the sheer capacity that is now on the Tvan - 350Watts, I really only need several hours a day to top up the batteries so I don't need to be in the most sunniest spot all day trying to charge the batteries [emoji106] I was getting 5-8Amps with 50% of the panels in the shade on Sunday at 3pm[emoji106]

So the way I looked at it was, polycarbonate sheet wall thickness is approx .5 - 1mm thick, you then have a 8mm air gap prior to the camper hatch roof, with some good air gaps crossing the rear hatch to allow that heat to escape. Yes the polycarbonate is a insulator, but they will get hot regardless, and yes they will still transfer the heat into the air gap below and that heat must dissipate from the cooler air surrounding the entire panel.

The other reason I went with the polycarbonate sheet was its inherent strength for its weight, outstanding stuff, the entire polycarbonate sheet for the whole area is under 3KGs [emoji6] and very very strong, with the added benefit of being able to stand a lot of UV and exterior punishment.

So maybe their is a better, backing material out their somewhere, but from my research nobody has found it yet, or at least promoted it.

The cost for the polycarbonate sheet was minimal, when and if they make something better, I'll just pull the frame apart and replace it - maybe [emoji6]

Cheers


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[davidjw14]

I have been following this discussion with interest first because I am about to mount an 80 watt panel
On the roof of my TVan and second because as I had a flexible panel glued to the roof of the service body on my patrol ute for a couple of years with no drama.  It worked exceptionally well regardless of the ambient temperature. In fact the alloy roof acted as a sort of heat sink and despite the black colour of the solar panel there was not much difference in surface temperature between the panel and the white powder coat  of the service body. 
Now I know there are considerable differences in the quality of panels on the market just as there are differences in the substrate - aluminium V polycarbonate- used for panels.  Without knowing for a fact what brands/ substrates are failing I can't help wondering whether a few (ie 1 in 100 installations) failures are getting way more attention than they deserve.  If this was a well documented and universal problem for flexible panels regardless of manufacturer or substrate market forces would pretty soon see the problem fixed or the product withdrawn from sale


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[weonatvan]

I have been following this discussion with interest first because I am about to mount an 80 watt panel
On the roof of my TVan and second because as I had a flexible panel glued to the roof of the service body on my patrol ute for a couple of years with no drama.  It worked exceptionally well regardless of the ambient temperature. In fact the alloy roof acted as a sort of heat sink and despite the black colour of the solar panel there was not much difference in surface temperature between the panel and the white powder coat  of the service body. 
Now I know there are considerable differences in the quality of panels on the market just as there are differences in the substrate - aluminium V polycarbonate- used for panels.  Without knowing for a fact what brands/ substrates are failing I can't help wondering whether a few (ie 1 in 100 installations) failures are getting way more attention than they deserve.  If this was a well documented and universal problem for flexible panels regardless of manufacturer or substrate market forces would pretty soon see the problem fixed or the product withdrawn from sale


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Well, I for one hope you're on the money with your thoughts/conclusion as it would save me a lot heartache  and put my mind at rest if you're correct.

As I already stated, I could have possibly bought my panels for half the price off Fleabay but I chose to go with Jaycar (bricks and mortar retailer) as I reckon they would have performed a bit more homework on their individual products if they're offering a 25 year warranty. Let's hope I don't need to test what is actually covered.

So, now I don't know whether I go ahead as planned and stick new panels direct to the rear hatch or not. I'm already up to 13 amps and I have a 20 amp Redarc solar regulator, so only 6 or 7 amps to go unless I change the reg.


"You don't know what you don't know"

Cheers dave

[davidjw14]

I am using 3M double sided automotive tape to stick the panel to the roof of my T Van.  Same stuff I used on the Nissan work body.  It worked extremely well. To me the issue of failure is the inconvenience caused not the cost of the panel.  Based on my admittedly limited research I bought panels with aluminium  substrate as these seemed to offer the best performance for my $$. Definitely not the cheapest but not the most expensive either. 

Having looked at how these things are made my guess is that failure is mechanical rather than electrical.  By that I mean the joints between individual cells fail rather than failure occurring within the cells them selves. This would be true for both flexible and glass panels as both types are made up of lots of seperate cells connected together in series.


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[Patrol Dude]

Ok we are camped down at  Woodford, mate has a single 100Watt panel the same as mine. He also brought with him a laser temp gauge. The single panel just up against the guy ropes read 44Deg



My panels read 22Deg with the polycarbonate backing!!!





Will do the test again at midday.


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Patrol Dude
4.2TD

[Patrol Dude]

Ok midday results:
Single panel no backing 43 Deg



Panels on camper with polycarbonate 34Deg



Don't really understand why the panels on the Tvan are cooler? They just are.


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Patrol Dude
4.2TD

[Howezit]

Don't really understand why the panels on the Tvan are cooler? They just are.

Maybe the loose panel is aimed more directly at the sun?
Although you do mention that it's midday, so maybe that's not the cause?