Epoxy for encapsulating cells (great DIY thread with photos!)

[artificer]

Michael a Trowel?
I don't think a trowel is gonna work..sylgard is almost like water..very thin..

Instead of trowel, think screed like they use in concrete. Something held a precise distance from the glass, and you draw it down the surface. I should end up with a fairly uniform thin coating of Sylgard on the glass. You don't want much. Lay down the cells, and then cover with the remaining Sylgard. Let cure, and possibly coat the back with something else.

I've never done this before, so I have a few questions. People mention 6x6 cells curling. How much do they typically curl? Can you flatten them by pressing down, or do they break? Which direction do they curl? along the tabbing wire or around it, or all over?

My Sylgard from Essex just arrived. 2 units only, but I ordered online without talking to anyone. Since I didn't see any information on minimum orders on the website, I would be interested to see if someone could do a one kit order online.

Michael

[DeltaFox 25]

From My experence that I have had with Slygard it is a little thicker the something that just runs. I would say the Slygard that I used was kind of like STP maybe a little thicker.

[mrnewbie]

Artificer...

"I've never done this before, so I have a few questions. People mention 6x6 cells curling. How much do they typically curl?

If when you solder the tabbing wire down..the tabbing wire curls up..the cell will curl up as well..Your goal is to make a nice flat cell..so try and keep your tabbing wire nice and straight...

So If your soldering the BACK side..and it curls up or down..then you would want to make sure the bow..in the tabbing wire your soldering is the just a little in the opposite direction to help..straighten out the finished cell..
I dunno kinda hard to explain..after making a few you will figure it out.
A little bow in the cell will not hurt anything, but it will take more sylgard to fill in the gap..and sylgard cost $.

"Can you flatten them by pressing down, or do they break?"

You cant really bend them back into shape.they spring back..outa shape.the tabbing wire solder flexes them back if it was not a perfect solder job.

Well when you sylgard your cell you can try something like a little weight on it (Spark plug type socket, shot glass, ect), but if it gets slygarded down..its real hard to get off without breaking cell ..as mentioned before someone else said they put a little piece of wax paper under weight, then just leave the wax paper..making sure your weight does not get sylgarded down..

Why do you need to spread the sylgard around..if you put your glass on a flat surface..and poor the sylgard on, it flows around pretty good..it will take it 10 min..but it will level itself

If you wanna scooch it around...think more like rubber ..like old windshield wiper blade...or even a flat piece of cardboard would work just fine. No need to go buy anything

Note..the Sylgard does not dry in 2-3hrs...takes 2-3 days..at least if you do it in the house like I have..also..it has no bad smell..

[DeltaFox 25]

Maybe you could use a paint brush to spread the slygard.

[bladerunner]

A Paint brush works fine, used cheap disposable ones, one for each batch.
Another word of caution, stir in the catalyst VERY well, one of my batches did not cure all the way, and I think not stirring enough was the reason. Stirring for about 10-15 minutes seems to work well for me. letting sit afterwards for about 15 minutes let all the bubbles rise to the top and pop, so you have less to deal with.
Because it is cured by the catalyst and not the air, you can put plastic on the back, and the sylgard should still cure fine.(mine did)
here is an outline of what I did:
1)Solder together all cells used in panel, instructions can be found lots of places on web MAKE SURE YOUR SOLDER JOINTS ON THE FACE OF THE CELLS IS SMOOTH AND FLAT. If it is not, you will have voids in the sylgard caused by the solder holding themselves off the glass.I kept them on a piece of cardboard, to more easily move them
2)make dam around area cells will occupy ( I used strips of plexyglass, silicone has worked for some people.
3)mix sylgard(10-15 min), clean glass w/alcohol, paint layer of sylgard on glass, If it was "grabby" I added a bit more, tried to get it pretty even.
4)slid the cell assembly (face down) onto the sylgard covered glass from the cardboard.
5)painted back of cells w/sylgard, this seemed to press them into the face sylgard pretty well, but then I had bubbles from the edges of the cells curling.
6)stretched cling wrap across the back, put weights on corners of cells to hold them down. (one some of my panels, I put a thicker plastic, and had to use heavier weights to hold it down as well, not sure which one works better. The sylgard supports the cells pretty uniformly, so you can put quite a lot of weight on the cell without cracking it. coffee cups and glasses seem to work ok sockets,large nuts, maybe flat rocks?

[DeltaFox 25]

that sounds real good . any pictures??

[lesticx]

What about using something like sikaflex?

http://www.sikaindustry.com/ipd-ma-products

It's not expensive, granted it's not see-through either. But I think I could just glue the cells with sikaflex to a hard plastic sheet from the bottom side, then put a plexiglas etc. on the front, and glue that in place with sikaflex.

Point is: this kind of substance is in essence elastic, it's meant to be used in boats etc.

What do you think of this idea?

[Eric]

I'm just starting to work with DAP 3.0 crystal clear and I'm really liking it so far. It really is as clear as I have seen out there and it has fantastic adhesion/flexibility. It's kind of expensive @ $7.50 (Home Depot) for a standard caulk tube but I used only two to three tubes total.

Like everyone else, I though Sylgard is a great product but there are a lot of things I do not like about it. #1 price. #2 isolated bubbles are almost a guarantee in any DIY application #3 Cure time is far too long.

I'm considering using this technique. I've already tried it once and so far I've been impressed.
Layer order
1/4 Glass
cells fully assembled
DAP crystal clear dabbed all around about every 1.5"-2.0" with no continuous beads.
Wait 24 hours.
Apply continuous bead of standard all weather silicone around perimeter of assembly.
Apply back sheet of your choice (clear allows you to see what's happening in there. on top ensuring that there are no gaps in perimeter bead.
Apply weight allow to cure for 24 hours.
drill small hole in back sheet in a known safe location
Gently Vacuum air out of space and seal immediately with adhesive foil tape. I used a Reynolds Food vacuum (used with their bags)
Some Cells may crack during vacuum process but I found that more crystal clear dabs helps to prevents this.
In theory you will have a fairly decent partially vacuum sealed assembly at about 2/3 the cost of Sylgard and without much bubble worry.

This is a work in progress but I will try to update people on the success/failure of it.
I was also considering adding silica desiccant inside the space between the cells and back sheet in lieu of vacuuming at all.
Thoughts?

[Mike90250]

..... I was also considering adding silica desiccant inside the space between the cells and back sheet in lieu of vacuuming at all.
Thoughts?

I'd vote for the desiccant, and skip the cell busting vacuum.

[BilljustBill]

I'm just starting to work with DAP 3.0 crystal clear and I'm really liking it so far. It really is as clear as I have seen out there and it has fantastic adhesion/flexibility. It's kind of expensive @ $7.50 (Home Depot) for a standard caulk tube but I used only two to three tubes total.

I've seen and used a crystal clear sealant called "Lex-Cell" that cost about the same as what you've used. I put a 1/4" thick window in my workshop's dust collection 55-gallon barrels. Two 3hp vacuum blowers are very strong. It took the LexCell to withstand any air leak because, like the Plexiglass, it is crystal clear and dries a bit tough and nothing like the soft flexibility of silicone.

I like the idea of seeing one's work and to be able to verify the perimeter seal. Is that Dap product ridged or soft and flexible?

[Eric]

I like the idea of seeing one's work and to be able to verify the perimeter seal. Is that Dap product ridged or soft and flexible?

It's not rigid but it's not ultra soft. It's about what you would hope for, let's call it a firm cushion and a quality seal. It says that it is designed it to protect in exterior applications where you want the beauty of the material to show through.
In my case I just want the sunlight to get through to those pretty little blue electric wafers and it seems to do that perfectly well.

Mike, yeah, I think I'll try the silica method (no vacuum) on my next panel.

[charlie_ruizpr]

I have don that but with sylgard. I'm going to start a new way, First put sylgard on to the glass , then put the cells ( already tyed togeather and bussrar also) on top of the sylgard , then put more sylgard ontop of the cells. this way it will completly take any air out.

That's a good idea, try it and let us kno.

[charlie_ruizpr]

Oh ok. Thats interesting to know. I was thinking of doing it exactly how he was, but maybe i should think about it. It sounds like it would be difficult to handle the cells once all connected though if putting them down after the sylgard. for example, the solar panel im making is a 72 cell (4 columns x 18 rows), and soldering the bus wires together while the sylgard is wet sounds too tricky, which means i'd need to somehow hold the entire array of cells and place it on the sylgard...which i can't see how it would work.

I remember the youtube guy poured the sylgard so that only 3 edges of each cell had sylgard poured on it, allowing the sylgard to seep under without creating bubbles, but i guess if you tried it four times and it didnt work...

Also, do you think 2 Sylgards will be sufficient for a 72 cell panel? Im thinking of getting them off ebay, unless that superioressex website can send international? im from australia.

I will be making 108 cell panel, how much sylgard would I need?

[charlie_ruizpr]

Thats a real good deal on the glass, Everytime I called Superior Essex they told me I had to buy 3 of them or they could not sell it to me. I'm going to put the Sylgard down on the glass and then the cell's and then Sylgard on top of that . It will take the air out.
I had alot of trouble with the 6x6's so I;m working with 5x5's now and I'm making a 72 cell panel. Good luck on your project.

Hey guys, let's say you put the frame on a table, put the cells in the frame with the glass of course, place the sylgard and let it set for a while and possibly add a litttle vibration with a motor to the table to see if it helps with removing the bubbles. Let me kno what you guys think

[DeltaFox 25]

Im was thinking about puting the cell's on a piece of plywood that is alittle biger then the frame and glass and make sure that these are tied togeather just like when you have them on the glass. put that aside , get your frame and glass ready and put your sylgard on the glass, now slide the cell's on the plywood off onto the slygard you already have on the glass , You probly will have some time to move thew cell's around if needed. Then add the other slygard , your done , let everything dry. I'm going to make a 72 cell 5x5 and I'm going to use this method.