Sunday, August 17, 2008

Solar Panel from New Tabbed Cells.

Building a 70 watt panel using 3.6 amp tabbed cells.

This is a "How I did it"with 35 of the cracked and damaged cells from the batch....not a "How You should do it" with your perfect 36 cells.

I decided to re-use some materials from an earlier, less successful, panel project.


The 900mm x600mm ply sheet with a 18mm square timber frame will only fit 35 of these big cells and will have a somewhat unusual configuration.
3 rows of 10 cells with 1 row of 5 at right angles.









This will give me a 69.3 watt 19.25 volt panel which is good enough for any system.

My major issue before actually getting started on this one has been the fact that to use the method I'm used to with small cells would mean soldering 10 big cells together face down and I would then need to turn them over when they're joined.
With the other panels I've built I've done the front soldering myself and trusted it enough to lift the strings of cells by the tabs.
The factory soldering on these much bigger cells is perfectly good enough to carry current but I'm not prepared to trust it to carry the weight of all those cells.

Consequently I've had to come up with another plan.

This is it.

I am going to tab the back of the cells with a cm or two of "tail" on the opposite side to the front bus.









Scraping the bus on these fresh cells may well be a waste of time but I did it anyway.











The flux pen makes it easy not to make a mess.
I couldn't take a pic of me actually soldering so you'll just have to take my word for it.

Using a plastic ruler as a straight edge the tabs are carefully folded at right angles to the back of the cell with the ruler touching the side of the cell.


















In case you're wondering this is what happened to the corner of my cell......
I got a teeny bit too close to my extractor fan when I was soldering the tabs. The fan made the most of the opportunity and went the munch!










With the cells laid out on the board I'll mark the position of the holes then drill all holes.
A small blob of Selleys all clear will go in the centre of the back of the cells and the tabs will be fed through their holes.
In most cases there will be the positive (back) tabs of one cell and the negative (front) tabs of the next cell through the same hole.









These tabs will be soldered together at the back of the panel.

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Okay....the above was written before a lot of the work had been done and all went to plan.
The cells were all laid out with a gap of 4 or 5 mm on the board in position and the holes marked for drilling and drilled.










I then bent all tabs at right angles to the cell using the plastic ruler against the edge of the cell to create 2 mm or so of gap between the edge of the cell and the right angle in the tab.










I put a blob of All Clear on the board for the centre of where each cell was to go and positioned the cells.
I started with the designated positive out pair of drilled holes and worked from there taking care to match neg to pos.




























The last cell to go into place was the negative out cell.


















The back of the board looks a lot worse than it actually is at this stage.









The back of this panel was complicated by the configuration so care was needed.
Alligator clips make perfect clamps! I bought mine from ebay seller allgateopeners at a great price and got excellent service.








I bent the tabs apart and soldered the join.









The longer joins on this panel took a bit more effort.









I used copper wire here both for the insulation and it's greater carrying capacity.









All the pairs of tabs are now soldered and trimmed and the longer joins are done with tab and copper wire.











The back cover trim is glued and screwed ready for the ply back cover.









The perspex front cover was put in place and carefully drilled for the 10 screws that will help the bead of All Clear hold it on.

My panel lead boxes haven't arrived so I can't quite finish the panel yet but I soldered a pair of wires directly and took it outside for a test run........
It was 5.15pm and it's winter evening and the panel did Great. Over spec at 19.7 volts and a credible 1.8 amps!....that's 35 Watts just on sundown in Winter!
I used the chipped and cracked cells out of the batch so I can't wait to see what the perfect ones can do!
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I ran out of paint so the back ply got a coat of estapol ( in Maple no less!). It should be okay but I'll keep an eye on it.

6 comments:

Part timer said...

This is some good information. How much time did you have involve on the whole project? Thanks Jon at solardiyinfo.org

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