Different output from different pannels

[tcrenshaw]

I have two Arco M51's with shattered glass, but they are still intact. Each panel has 36 round dark black type cells. I have four home built panels and they have 36 cells each (from eBay) which as everyone has seen are the 3x6 blue colored cells.

Today I had the chance to setup all my panels in pretty much the same area and take some measurements. I wanted to mark each panels reading on it so I'd have a reference later on. The panels were all at about the same angle to the sun.

Here's what I'm seeing -

Arco M51 Panel #1 20.6V @ 1.25A

Arco M51 Panel #2 20.6V @ 1.39A

Home Built Panel #1  20.4V @ 1.98A

Home Built Panel #2  19.8V @ 2.1A

Home Built Panel #3  19.6V @ 2.11A

Home Built Panel #4  19.5V @ 2.22A

My question is, are the home built panels showing higher current because of the larger surface area of the eBay cells compared to the smaller circular cells used in the Arco panels?

[RatOmeter]

Depending on the cell technology (junction material), each cell will have a characteristic voltage, no matter the size.  Current is a function of the area of junction, therefore the area of the cell. Part of evergreen solar's design goal is to optimize the area of the cells, hence the rectangular shape.  For the record, the traditional round solar cells are so because they're cut into wafers from a round silicon block, then processed to be made PV cells.

[BT Humble]

My question is, are the home built panels showing higher current because of the larger surface area of the eBay cells compared to the smaller circular cells used in the Arco panels?

Yes.

And being newer, it's possible that they have a slightly higher efficiency per square inch too.

BTH

[troy]

I think they're better because you did such a fabulous job building them, so they're trying harder for you.

From the tongue in cheek dept,

troy

ps, I really think it's a surface area issue, plus the newness.  Although it does prove that you made excellent connections and very consistantly.

tr

[jimjjnn]

Solar cell technology has improved tho the different types seem to improve things.

Amps and volts seem to be the same no matter what tech it is,

I have 20 1X2 centimeter cells  acquired in 1960.

The output of them are still.045 amps @

.5 volts.

I cut one in 1/2 (very carefully) with an old diamond glass cutter.

Volts remained the same and amps was now

.023.

Amps increases with the area while volts remains the same.  

[tcrenshaw]

Guess that's my mothers influance, putting a little TLC in there with the mix! HA! Well I'm happy with the outcome whatever makes them work. One more panel this weekend and it's time for a charge controller, batteries, and an inverter. Even though it's expensive, even with home made panels, I'm enjoying it.

[tcrenshaw]

Some people are reporting 2.75A out of basically the same configuration I'm using. I attribute some of that to my cheap meter, there cheap meter or both. My meter is a very cheap US$39.00 meter with a 10A max. Plus or minus .5A would not surprise me with it. I do like the almost double output of my panels with less than 1/4 more surface area though. It's almost time to break into that second box of cells and build another five or six panels. Maybe I shouldn't use the word break!

[sandovalch]

My home made panels have about 2.75A short circuit current, with glass in front of them. Without the glass the panels can go up to 3 to 3.2A. That is at 2 o'clock without a cloud. But then again I'm at latitude:13.9800 longitude:-91.0700 or Guatemala City, so we could have better sun irradiation.