Posted by Lu Wei on July 24, 2013, 7:45 am
On 2013-7-22 16:57, Bernhard Kuemel wrote:
>> And I think there is a little error on the label: The
>> diagonal can't be 195mm (should be 200mm I think), or 17.75% efficiency
>> and 4.24W will not agree. Anyway it's really cheap and worth the price.
>
> Interestingly I got cells with 195 mm and 200 mm diagonal, both 156*156
> mm square. It's only a little difference at the corners.
>
17.75%, 156*156 and 195 diagonal will give 4.197W. The difference is
small but could not be mis-labeled. Maybe the package is not original.
--
Regards,
Lu Wei
PGP key ID: 0x92CCE1EA
Posted by Kevin McMurtrie on July 21, 2013, 6:16 am
> Hi asp, sec!
>
> I bought 300 "Class/Grade A" solar cells [1]. Just when I wanted to
> resell some of them I discovered that most of them (all that I checked)
> have a few (about 2-6) complete or partial gaps in the finger traces
> that pick up the electricity and forward it to the bus bars. There are
> also marks on the edge that look like overheated spots:
>
> http://www.bksys.at/bernhard/solarzellen/defects/-gallery.html
>
> Many of the gaps appear in sequential cells in the same position, so it
> seems it's a fabrication mask error, not a shipping defect.
>
> Are these significant defects? Do they reduce performance or life time?
> Would you care about them?
>
> I have a bunch of Grade B polycrystalline cells with no such defects.
>
> Thanks, Bernhard
>
>
>
> [1]
> http://www.ebay.at/itm/121129695438?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m14
> 97.l2649
Those conductor breaks look harmless because there are no islands. The
edge colors are normal.
A problem with crappy solar cells is internal leakage. They'll perform
to spec in full direct sunlight but you'll get zero volts indoors or in
the shade. There's a lot of IR indoor near lamps and a lot of UV
outdoors in the shade so a decent solar cell still has some use without
direct light. You can always do a side-by-side comparison with a known
quality cell.
--
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Posted by Bernhard Kuemel on July 22, 2013, 9:21 am
On 07/21/2013 08:16 AM, Kevin McMurtrie wrote:
> Those conductor breaks look harmless because there are no islands. The
> edge colors are normal.
>
> A problem with crappy solar cells is internal leakage. They'll perform
> to spec in full direct sunlight but you'll get zero volts indoors or in
> the shade. There's a lot of IR indoor near lamps and a lot of UV
> outdoors in the shade so a decent solar cell still has some use without
> direct light. You can always do a side-by-side comparison with a known
> quality cell.
My cells have 0.46 V and 39 mA inside in the shade. I put them in a
stainless steel pan as backside contact and touched the middle bus bar
with a multimeter probe. My desk is next to the window, it's a bright
day outside, no direct sun hitting my window, just some diffuse reflections.
Bernhard
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>> diagonal can't be 195mm (should be 200mm I think), or 17.75% efficiency
>> and 4.24W will not agree. Anyway it's really cheap and worth the price.
>
> Interestingly I got cells with 195 mm and 200 mm diagonal, both 156*156
> mm square. It's only a little difference at the corners.
>