I bought a pair of $1/watt W Solar 45W monocrystalline panels from Solar Blvd which arrived today. First thing I noticed was there were 40 cells on the panel, not 36 like usual for a '12V' panel, but the open circuit voltage was not 4 cells higher.Took it outside to do some measurements and when checking shading performance I was VERY surprised to not see the amps drop when I shaded one cell, then another, then another.Hmm, I don't see blocking diodes on the cells. Blocking some of the other cells, there was an immediate drop. "What is going on?"Closer inspection showed that though this panel has 40 cells, only 36 are wired up. 4 cells appear to be wired up but are not as seen in the 2nd photo.I guess it was more important to make a square'ish panel vs a rectangular panel even if it meant wasting 11% more cells. Too bad they were not wired up - would have liked to have used that extra voltage for an MPPT controller.Performance wise, Isc and OCV matched the label even at 4:30PST sunlight with the panel facing the sun.Green arrows show cells not wired upGreen arrow shows connector ribbon not extending beyond edge of cell.

Would you have bought it if it were missing four cells? ;)

my guess,it was supposed to be 40cell panel, but something in that row tested badso it was wired and sold as a 45w 36cell paneli know CPU chips get graded, if they don't pass the highest testing levelsthe get marked and sold at the grade they do passa chip that was supposed to be quad core, might be sold as a lower grade duo core

You could always remove it from the frame and wire it up... It might work.

MrWizard wrote:my guess,it was supposed to be 40cell panel, but something in that row tested badso it was wired and sold as a 45w 36cell paneli know CPU chips get graded, if they don't pass the highest testing levelsthe get marked and sold at the grade they do passa chip that was supposed to be quad core, might be sold as a lower grade duo coreI was thinking about CPUs and yield and clock rating as well. Either their spec is only 36 cells and those 4 are available to jumper in to make spec when necessary, or they sell panels with fewer working cells as a different model.Do the cells make power in sunlight similar to the connected ones?If you find they have the full output of their peer cells under various conditions, I don't see any reason not to just Jumper them in, in series, and bump up your panel voltage a couple of volts. If you have MPPT you could even take advantage of the extra watts.What actual model panel is it? What are the specs? Sometimes low watt battery maintainer type panels are intentionally lower voltage because they are designed to run direct attached to a battery bank without a controller. There could be two versions, and the one using all panels has the extra volts to work better with a controller in the middle.Jim

I noticed on the spec. at the website, that the 45W. weighed 20 #. The 40W panel next to it weighed 10 # while only being a inches in L & W shorter.As I would plan on a portable panel being used as a battery maintainer while my RV was in storage for my house and chassis batteries, carrying this to the roof of my RV would be noticeable.Does it really weigh twice as much, 20# vs. 10#.Why would that be for almost the same size panel?

Solar so cheap that cells can be wasted | Good Sam Community

15 Replies

RCtime
Explorer
May 11, 2013
I noticed on the spec. at the website, that the 45W. weighed 20 #. The 40W panel next to it weighed 10 # while only being a inches in L & W shorter.
As I would plan on a portable panel being used as a battery maintainer while my RV was in storage for my house and chassis batteries, carrying this to the roof of my RV would be noticeable.
Does it really weigh twice as much, 20# vs. 10#.
Why would that be for almost the same size panel?
HiTech
Explorer
May 11, 2013
MrWizard wrote:
my guess,
it was supposed to be 40cell panel, but something in that row tested bad
so it was wired and sold as a 45w 36cell panel

i know CPU chips get graded, if they don't pass the highest testing levels
the get marked and sold at the grade they do pass

a chip that was supposed to be quad core, might be sold as a lower grade duo core

I was thinking about CPUs and yield and clock rating as well. Either their spec is only 36 cells and those 4 are available to jumper in to make spec when necessary, or they sell panels with fewer working cells as a different model.

Do the cells make power in sunlight similar to the connected ones?

If you find they have the full output of their peer cells under various conditions, I don't see any reason not to just Jumper them in, in series, and bump up your panel voltage a couple of volts. If you have MPPT you could even take advantage of the extra watts.

What actual model panel is it? What are the specs?

Sometimes low watt battery maintainer type panels are intentionally lower voltage because they are designed to run direct attached to a battery bank without a controller. There could be two versions, and the one using all panels has the extra volts to work better with a controller in the middle.

Jim
atreis
Explorer
May 11, 2013
You could always remove it from the frame and wire it up... It might work.
MrWizard
Moderator
May 11, 2013
my guess,
it was supposed to be 40cell panel, but something in that row tested bad
so it was wired and sold as a 45w 36cell panel

i know CPU chips get graded, if they don't pass the highest testing levels
the get marked and sold at the grade they do pass

a chip that was supposed to be quad core, might be sold as a lower grade duo core
Michael_in_MN
Explorer
May 11, 2013
Would you have bought it if it were missing four cells?

;)

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Solar so cheap that cells can be wasted

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