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Discussion Starter · #1 ·
Have just bought this 100w semi flexible panel for my van - http://www.bestecoshop.com/100w-semi-flexible-monocrystalline-solar-panel.html
Went for this panel as it comes with a 2 year warranty on the panel itself and 25 year warranty on cell degradation, some of the ebay ones i inquired about came with a 30 day warranty !

Anyway, i need to fix it to my flat austop poptop, im reluctant to fix the whole panel with sikaflex incase it ever needs to come off, so im thinking of maybe a small blob of sikaflex in each corner of the panel and then using a strong automotive double sided tape for the rest of the panel, like this - http://www.ebay.co.uk/itm/Black-Dou...Scrapbooking_Glue_Tape_EH&hash=item2a2449fe6d

Anybody see any issues with this, my thinking is the sikaflex in the 4 corners will mount it securely and a few strips of the foam tape along the length of the panel will lift it off the roof a few mm to allow a bit of airflow beneath the panel ?
 

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I think I'd be inclined to fix a frame of some sort to the roof then slide the panel in and fix somehow. small dob of Silkaflex migth not be enough to hold it when traveling at 70 mph. I know it's good stuff thoug.
 

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A word of advice regarding these panels. The junction boxes are not IP rated and will fill up with water if they're installed on a flat roof. Open yours up before you fit it and fill it full of silicone. I've got 2 of these sikaflexed to my roof and I need to get them off to repair them because the junction boxes have filled up with rain and corroded the contents.

As for Sikaflex, I put a couple of beads all round the edges and they're not budging, which should be good but not now I need to get them off :(
 

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Discussion Starter · #4 · (Edited)
Cheers for that Alan, will have a gander under the cover before I fit it to roof T:
Edit : my junction box is full of silicone but will add some more before fitting to make sure where the cable entry is, is fully sealed.
What size panels have you got Alan ?
Have tested the panel and am getting around 5.5 amps in full sun, looking at it now, i can fit another 100w along side it but wondering if that might be overkill ?
 

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The damaged panels are 2 x 50W semi flexible, but they're coming off now they're damaged to be replaced by 2 x 80w rigid panels. If I can repair the damaged ones, I may put one back on the roof and possibly put the other on my roofbox to make up for any shading when it's in use.
 

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Discussion Starter · #6 ·
Had the van on mains charge till 11:30 last night then unplugged charger (batteries fully charged)

Waeco CR50 was down to temp on setting 4, so by my maths between 11:30 last night and 7:30 am this morning at an average consumption of 1.4ah, it would have taken around 11ah from the batteries.

By 10:30 this morning the fully charged led on solar regulator was flashing and showing a battery voltage of 13.6volts.
hooked my multimeter into charge controller output and at the moment im getting around 3.5 - 4 amps in the sun and 0.8 - 1.5 amps when a bit of cloud comes by, happy with that T:

Will test current again around midday when we have full sun (cloud dependent).

Hearing of Alans problem, think ill invest in a secondary cable cover sikaflexed over the panels terminal cover to protect from the elements.
 

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A word of advice regarding these panels. The junction boxes are not IP rated and will fill up with water if they're installed on a flat roof. Open yours up before you fit it and fill it full of silicone. I've got 2 of these sikaflexed to my roof and I need to get them off to repair them because the junction boxes have filled up with rain and corroded the contents.

As for Sikaflex, I put a couple of beads all round the edges and they're not budging, which should be good but not now I need to get them off :(
please dont use silicone unless you have to,this is the stuff to use as it seals but sets like soft jelly and is easy to pull it out if you need to http://www.tlc-direct.co.uk/Products/WKMF170.html
 

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Discussion Starter · #8 ·
Having been made paranoid by Alan's damaged panels, ive decided to disassemble and redo my panel to junction box.
Although it was filled with silicone it didnt fill me with confidence so stripped it out, also found the junction box itself to only be stuck to the panel with silicone which I dont trust.

So today ive unsoldered the fly leads and then unsoldered the panel tabs from the box, ive cleaned everything up and will refit it all but with Marine grade sikaflex rather than clear silicone.

Rather do it properly now and then be confident in its water tightness. apart from this its a great panel and has already proved to put out the stated amperage.

box removed from tabs.
 

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The main problem with these panels is overheating. You should mount with an air gap under them to allow cooling air to circulate. A lot of forum members have these bonded direct to the roof and they have failed after about a year and the warranty wont cover them. Be warned!
 

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The main problem with these panels is overheating. You should mount with an air gap under them to allow cooling air to circulate. A lot of forum members have these bonded direct to the roof and they have failed after about a year and the warranty wont cover them. Be warned!
disheartened now after having a good read up on solar panels to put on the roof. surely the nature of semi-flexible panels is that they're designed to fix directly to a surface ? is this made worse if the're fitted to a metal roof as apposed to a grp pop top and even worse still if its a black roof ? ok with the fact that the terminal box needs to be sealed well after reading Alan surrys probs. Still like the idea of 2 maybe 3 flexi panels fitted between the roof ridges, any more experiences with this, it'd be good to hear , cheers
 

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Discussion Starter · #11 ·
I have contacted the manufactures of my panel and had a reply to say they have never had any returns of failures caused by overheating, however i may mount mine on 4 strips of 3mm upvc edge trim to lift it off the roof slightly.
Having said that, the day after mine was delivered I had it on my pop top and when the sun was directly above it at 2pm it was making 5.5 amps which is pretty much the spec.
It had been in full sun on the roof since 7:30am as well so should have been affected by heat :*
Ive searched this forum and google for flexible panel failure due to heat and only found 1 thread on here where heat was suggested as a failure but the manufacturers said it was due to vibration causing micro cracks.
 

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Discussion Starter · #12 · (Edited)
Sun permitting tomorrow, im going to carry out a little experiment.

I have a digital gun thermometer so I will place the panel flat on my roof and then after 30 mins measure the panel temperature.
I have made a frame from pvc edge trim which will lift the panel away from my pop top roof by 5mm, ill then give it 10-15 minutes and see if indeed the panel is much cooler.

This thread http://www.vwt4forum.co.uk/showthread.php?t=237235 seems inconclusive, if the failure was down to heat, then mounting on the 5mm frame will help, but if the failure was indeed to vibration then surely it would be best to bond the panel direct to the roof, ensuring whole panel is bonded and not just bonded around the edges.
 

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look forward to hearing what results you get, i assume the temperature leads to gradual degrading of the panel rather than an instant failure, just wonder how many are down on output due to corrosion in the terminals and not the panel ?
 

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Discussion Starter · #14 ·
If it is heat, then yes, im guessing it will be over time.
At the moment i'm just interested in exactly how much cooler the panel will be with the 5mm airgap underneath.
If it's a considerable amount then thats how I will mount it.
My roof is white GRP so im pretty confident its not going to hold the heat like a black metal roof would.
 

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Discussion Starter · #15 · (Edited)
And the results are in :

With 5 20mm wide upvc strips mounted longways on the panel (so air could freely move from one end to other), these are the readings.
All readings were taken during 20 minute window of unbroken full sun. Each time I measured the temp of the central solar cell on the panel, then the temperature of the surrounding roof and then the charge current.

Time ---- panel temp ------ roof temp------- charge current

11:50 ------- 46 oC ------------ 36 oC -------- 5.0 amps ------- 10 oC temp difference between roof and panel
11:54 -------- 50 oC----------- 37 oC --------- 5.5 amps ------- 13 oC " "
11:57--------- 54 oC------------ 39 oC---------- 5.8 amps ------- 15 oC " "



The next three readings are with the panel taken off strips and laid flat and flush to the roof,again, still the same period of unbroken sunshine.


Time------ panel temp-------- roof temp-------charge current

12:00 ------- 48 oC --------------38 oC ---------- 5.5 amps ------ 10 oC temp difference between roof and panel
12:04-------- 48 oC ---------------38 oC -----------5.6 amps ------ 10 oC " "
12:10---------49 oC ---------------38 oC -----------5.8 amps.------ 11 oC " "

Not sure what the readings would be on a metal roof (mine is white GRP poptop) but by my observations, rather than causing the panel temperature to rise, sitting it flush to the roof actually dissipates the heat from the panel better than having it raised with a 5mm airspace below it.
 

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interesting results, going to get some temp readings of my black metal roof later today, it'll be a good comparison
 

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I've got one of my flexible panels off and cut back a bit of the top layer to get at a fresh piece of conductor and it's still producing 21v, so with a bit of soldering and repairing, I should get them both back in working order. Depending on how well my new panels perform, I may put one of the flexible panels back on the roof & sell the other one on to recover a bit of my costs. If anyone's looking for a cheap 50w semi flexible panel, let me know.

While we're on the subject, can anyone confirm whether or not I need to replace the blocking diode if the unit is connected to a charge controller?

Cheers, Al.
 

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I've got one of my flexible panels off and cut back a bit of the top layer to get at a fresh piece of conductor and it's still producing 21v, so with a bit of soldering and repairing, I should get them both back in working order. I Depending on how well my new panels perform, I may put one of the flexible panels back on the roof & sell the other one on to recover a bit of my costs. If anyone's looking for a cheap 50w semi flexible panel, let me know.

While we're on the subject, can anyone confirm whether or not I need to replace the blocking diode if the unit is connected to a charge controller?

Cheers, Al.
When I changed my panel from a single 38v circuit to 2 19v circuits, I took the diodes out of the black box. Neve had any trouble with it. My panel goes in 20amp charge controller.
 
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