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Old 09-11-2012, 12:20 PM   #21
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I've been looking at the Morningstar Tristar 45 mppt and the BlueSky 3024 mppt unit. They are a bit more than I need but but there seems to be a gap between 15/20A units and 30A+ units.

2 144W unisolar panels would feed into this.
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Old 09-11-2012, 01:24 PM   #22
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With the BlueSky 3024 you'll need to wire your two panels in parallel - it has a recommended maximum input voltage of 45 volts and each of the ePVL 144's put out up to about 35 volts. One thing about the Morningstar is you can run at roughly 70 volts by wiring your two panels in series, so you can gain a couple of watts by avoiding transmission loss.
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Old 09-30-2012, 11:21 AM   #23
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I had some time yesterday to perform the initial surgery on one of the ePVL-144 panels.

Important disclaimers - Based on what I've read on the Internet, the internal structure of the older PVL panels vs. the newer ePVL panels is probably different. Similarly, I only have cut into an ePVL-144 - so I don't know if the inside of a -68 or a -136 are different. So what you see here may not be exactly the same if you don't have an ePVL-144.

Here are the steps:

1) Look at the front of the panel - it's obvious where the individual cells are - they are about 9 inches long - and there is clear black line with silver edges you can see between every two cell. This is where you will make the cut - only in-between two cells.

2) Remove the white peel away plastic from the back of the panel - I used a single edged razor blade - in the area where you want to make a cut.

3) Peel away the sticky black mastic from the back of the panel - about 3/4 inch on each side of where you will make the cut. It comes off more easily then I thought it would. I found mineral spirits worked to clean up any leftover spots.

4) Now look carefully at what you are seeing. With the black mastic gone, you can see what used to be the black line in between the cells is actually empty space - about 1/8" of clear, transparent plastic between the cells. You can now also see the wiring bus that ties the panel together, including a bypass diode.

The colors you see are important - the copper is obviously the wiring bus. The silver color is stainless steel, and is the cell itself - the actual cell is silicon deposited onto a stainless steel sheet. The remaining black color is internal insulation within the assembly - this is going to be important later - because you will short out the panel if you don't keep the various elements insulated from each other. The little black square soldered onto one of the copper conductors (at the bottom of the picture below) is a bypass diode.

The reason I think the layout may have changed between the PVL and ePVL series panels, is that in this new ePVL panel the bypass diode is in a pretty good place if you are trying to cut panels - I saw references on the Internet to the diodes running across the area you need to cut. In this panel, the diode sits on the back of the cell, separated from the cell by black insulation. It also has copper leads, which should make the panel much easier to cut and re-assemble.

5) Use a brand new single edge razor blade to cut through the panel, right in-between the cells. The material is tough and it will take several passes. Very carefully stay in between the cells, and make sure to leave yourself enough of the copper lead connected to the bypass diode to have something to solder to later.

6) Once you separate the panel, you will see there are two more conductors that are buried within black insulation - one on either edge of the panel. So there are a total of four conductors. When re-assembling the panel, you will be re-connecting these conductors with solder and wire.

This is where I stopped last night. It is relatively safe to assume that the four conductors mean that the overall panel contains two strings of cells - it would make sense that every other cell is connected in series to either the left or the right set of conductors, and that the two strings are connected together in parallel at the end of the panel.

Having two separate sets of conductors also means that it's probably that you could find a bypass diodes on both the left or right edge of the panel - on the right side of one cell, and on the left side of the next one. So which side the diode is on probably depends on whether you cut above an odd cell or an even cell.

If I have some time later today I'll put the voltmeter on the cut panel pieces to try to verify what each of the conductors actually is carrying, and I'll start to work out a procedure for re-connecting the cut pieces.

The four pictures below are

1) The upper side of the panel, showing the line between two individual cells.
2) The underside of the panel, in the same place, with the mastic removed.
3) A closeup of the bypass diode
4 A closeup of the cut edge, so you can see the embedded conductor that is otherwise hidden by black insulation.
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Old 10-02-2012, 03:14 PM   #24
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Thanks for the update. I have still have not come across any ePVL-68 panels so would be interested in splitting the 144 panels.
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Old 10-03-2012, 06:27 AM   #25
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Quote:
Originally Posted by bgordon View Post
Thanks for the update. I have still have not come across any ePVL-68 panels so would be interested in splitting the 144 panels.
Amazon: Amazon.com: ePVL-68
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Old 10-03-2012, 10:29 AM   #26
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unisolar | eBay
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Old 10-03-2012, 11:28 AM   #27
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Made some progress on re-wiring the panels.

It was not hard to expose the four conductors and solder leads onto them. I used a razor blade to cut the outer membrane and expose each conductor - on each side of the panel, one of the conductors is best reached through the front of the panel, and the other through the rear. Then I soldered 12 gauge wire leads to each internal conductor. Took about 30 minutes and I was very very careful.

In testing the panel with my volt-meter, my latest theory is that the conductors on the right side of the panel are the main power bus, and the left side carries bypass current. I had previously thought that both sides of the panel were power busses. Why do I think this - when I measure the voltage on the right side of the panel, it is producing about 14 volts. On the left side, about two volts. This is consistent with one cell on the left, and seven cells on the right. It really doesn't matter since I am going to re-connect everything anyway, but I was curious.

Don't panic if you cut the panel and you no longer measure voltage at the connectors. You need to close the circuit on the power side of the panel - see the bottom right of the picture - if you are going to measure the output of one segment without re-connecting the whole panel back together. Otherwise you will be trying to measure an open circuit.

As you can see in the picture below, the panel segment is still happily producing 14 volts- and survived an 80 pound Labrador retriever walking around on it pretty well too!

My main concern at this point is physically reinforcing the connections. I don't want the solder joints to carry any mechanical stress, or they will eventually break off.
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Old 10-05-2012, 03:41 PM   #28
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$99 buys the 9'4" x 15.5" 68 watt panel at Solar Blvd...

Unisolar PVL-68T 68W, 12V Thinfilm Roof Laminate
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Old 10-12-2012, 07:26 PM   #29
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More progress to report.

I'm almost ready to install the cut panel on the roof of my airstream.

I ended up cutting the 18 foot long ePVL-144 panel into three segments, each approximately six feet long. Each segment contains either 7 or 8 cells, there are 22 total cells in the panel.

I needed to split the panel into three segments so it would fit in the remaining open, unshaded spaces on my roof. I've got a 27 foot safari, so your mileage will vary depending on the length of your trailer.

Below find a few more pictures - once you connect leads to the conductors inside the panel, it's easy to hook the segments back up together again.

I'm pleased to report that each segment is working fine, and producing the expected amount of voltage - and the whole panel is similarly working correctly when wired back together.

I ended up using 2 inch wide, 20 mil thick PVC tape to mechanically fasten the leads to the cut ends of the panel - I didn't want the solder joints to carry any stress. What I did was liberally apply weldwood adhesive (solvent based, that I also use for laminating veneer) to the edge of the panel and to the leads, and then also to the back of the PVC tape - and then I sandwiched the end of the panel and the leads in between two pieces of PVC tape. It seems to be very strong and solidly bonded to the panel - we'll see how it holds up over time. This type of adhesive is waterproof and the bond get stronger over time.

You can see the end of one of the panels with the weldwood cement applied in one of the pictures below. I am sure there are other creative ways to do this, I happened to have these materials laying around in my shop.

I would say this is not a project for the faint of heart - you need to be comfortable with a soldering iron and with the idea of cutting into a $150 solar panel.
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Old 10-13-2012, 12:33 PM   #30
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Below is are shots of the re-connected panel happily producing 45 volts... You can see the twenty mil pvc tape I used to protect the panel cut ends and provide some extra strength to the pigtails I soldered onto the panels.

Next step is to install on the roof - and that will be the easy part.

The final step will be to reconnect the various sections of the panel after the sections are adhered to the roof of the trailer. This will be super easy, I'm using 10 gauge THHN stranded copper wire in between the sections, and will solder it to the pigtails I attached to the panels as described in earlier posts.

So I'm about to declare success - happy with the way this project turned out, and my total cost for the complete project will come in at about $700 in parts for a 288 watt system, before the 30% federal tax credit.
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Old 10-13-2012, 12:56 PM   #31
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Good job Dan,
how are you going to hold the wires down on the roof. I will need to connect three of these panels to each other and there will be several feet between panels.
Also how did you remove the roof protection for the tv antenna?(the metal plate that the antenna rests on when not in use)
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Old 10-13-2012, 01:18 PM   #32
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For the TV antenna support -

On my trailer, the support that the antenna rests on was a simple piece of aluminum bar bent into a U-like shape, with one leg on each end. Each leg was attached with one rivet to a plate that was glued onto the roof.

What I ended up doing was cutting the curb-side leg off of the support, and using a new piece of aluminum bar to extend the support further toward the edge of the trailer, so the panel could fit underneath. I also bought a small piece of aluminum plate to glue down to the roof of the trailer - and used a small stainless steel screw in place of a rivet to attach the new plate to the new aluminum bar - so there are no roof penetrations.

For the wiring -
I plan to use a combination of wire ties and adhesive caulk (something like Vulkem) to mechanically fasten the wiring between the panels to the roof. They won't be under very much stress up there - they don't have that much mass and are relatively protected from the wind - so I'm not horrible worried about them flapping around too much. I also plan to heat shrink the individual wires together into cables to make them neater and easier to manage. On my roof layout, there isn't too much distance between sections - looks to be about three feet between the first and second section, and two feet between the second and third.

Hope this helps.
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Old 10-13-2012, 02:49 PM   #33
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Good solution, thanks,
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Old 10-20-2012, 11:03 AM   #34
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Pleased to report everything is installed and working. Pictures below. Panels are wired together in series and generating about 90 volts DC. You can also see the supply cable coming up through my refrigerator vent. The colored wires are 10 gauge stranded THHN connecting back together the four conductors in each panel segment. All wire joints are soldered and shrink-tubed. I used a combination of zip ties and aluminized RV roof caulk fasten the wiring to the roof of the trailer.

No major issues in completing the project - just had to get over the fear of cutting up the panels.

What you are seeing in the pictures - on the curbside is an uncut ePVL-144 panel. On the streetside is an ePVL-144 panel cut into three pieces and re-connected.

Now we will see how it lasts...
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Old 11-10-2012, 03:31 PM   #35
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Thanks for taking the lead on this Dan. I finally got my ePVL-144 panels ordered. The 14.5" width of the ePVL is critical for my application. I'll be splitting them in half and will have 4 sections appx. 9ft in length to go up top.

I'll take some pictures and post when I go through the install sometime in the next few weeks. My friend works at a solar installer so I may lean on them for some help with misc parts, etc.
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Old 11-10-2012, 03:42 PM   #36
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Also, what kind of feedback do you have on your Intronics charge controller? I'm intersted in springing for the Tristar 45 MPPT but it's twice the cost at $400. Thanks.
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Old 11-10-2012, 09:41 PM   #37
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it seems to be working fine. batteries have been topped off just fine for the last month. i would prefer to have a remote monitor though...
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Old 12-03-2012, 03:09 PM   #38
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Unisolar e-PVL 144 install

I've got the 2 panels cut and installed on my Boles Aero. Cutting and resoldering leads (and then making sure they were protected) took quite a bit of time. The ePVL-68 panels would've made for a cleaner and less time intensive install, but I could not find any at a price comparable to the ePVL-144s. The e-PVL model was critical (as opposed to the older PVL model) because I needed the slimmer width so I could fit them side by side between my roof vent and the edge of the roof (picture #4).

The splicing of the panels was a bit tedious but not very complicated. Thanks to Dan for taking the lead.

I cut the panels in half and dug out the two leads from the rear. I used an exacto knife to cut and peel back the mastic and the plastic layer. (pic #1)

I dug into the top of the panels but did not find any copper leads - just the stainless sheet that backs the solar cell. My impression is that there is one lead on each side accessible from the bottom of the panel. I wired them back up and they seem to work fine - getting just under 48 volts each. (pic #2/3)

After I soldered up news leads I wrapped the exposed wires for protection. This was the toughest part as I had to cut around parts of the wire and wrapped it multiple times in 20mil PVC plubming tape to ensure a good seal and make for a clean install.

Upon installing I used Trempro to seal parts where the mastic had been remove, around the connections and over the wires.
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Old 12-03-2012, 03:16 PM   #39
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wire routing

I do have a question about routing the leads. Originally I thought I would run them up through to the fan vent, but I see now that I could have a much cleaner install if I ran them down through the panel next to where where they terminate (pic below - yellow circle).

That would keep the wires covered underneath the junction box on the panel - protecting the wires as well as providing additional insurance against water leaks. And the aesthetics would be cleaner.

There is a risk because there may be a copper lead embedded in that panel underneath. The next cleanest install would be to send them into the roof right below the panel.

I think I could've gotten some insight on the path of the embedded copper if I had peeled back the mastic underneath the junction box. I'm not sure if anyone provide insight or if there is a schematic of this panel floating around.

I did see some panels that were being sold on eBay without the adhesive so perhaps I can inquire there.
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Old 12-04-2012, 12:17 PM   #40
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I did find these images from a non-laminated PVL-144 for sale on eBay. I'm not sure how much the design changed on the ePVL model so it's not clear what the underside of my panels look like at the junction box, but this should add to the thread.
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