Broken Panels and optimization

[HackNFly]

I recently purchased some used panels, only $40 a piece, as they were cracked.

Model: Q.Plus-L-G4.2 - 335 W

Electrical Watts: (STC) 335 W Max Power

Voltage: (VMPP) 37.33 V

Max Power Current: (IMPP) 8.97 A

Open Circuit Voltage: (VOC) 46.81 V

Short Circuit Current: (ISC) 9.54 A

Max System Voltage: (UL) DC 1500 V

I have 24V EVE 280ah battery bank, and an MPP HV LV 2424, the green one.

I have bulk and float at 27.8v. I have an OverKill Solar 80A 8S BMS.

I tested the cells when purchasing them and they were putting out the same volts as the uncracked cells. At home I tested the cells on an AMP meter and got close to 9A on short. My battery is currently at 80AH / 280 AH, and I top balanced the cells when I first got them.

I'm currently only getting 300 watts with 2 cells in series with the sun out and bright. It's almost May in North Carolina. I had the panels completely flat when the sun was out at it's highest.

Are the panels likely defective? Is there some way to check? I'm in the process of figuring out optimal placement. Unbroken panels were $135 a piece so even at half power I suppose it works out but I want to be able to tell. I'm planning on using some UV sealant on the cells that were badly cracked. I'm currently testing the cells without any sealant.

 

[sunshine_eggo]

Next time you test, add a load > what your panels can produce.

 

[kanelr]

300 watts is very good for a 335 watt panel in May not facing the sun directly.
Also I think that like everything else the max ratings are in near perfect conditions whatever that might be.
That being said. Yesterday while adding four more panels on our roof i cracked one with a stray screw (sigh). Tested and had same specs stillso I installed in the group. Thought about what to fill in the glass cracks because rain would do something bad soon enough .I decided that a repaired panel lasting a long time was better than a broken panel at 100 % but dying in a few months either optically or electronically, I cut a tight fitting piece of 1/8"thick plexiglass and silicone sealed it in place with only the frame not the glass getting the sealant. (see picture- fixed one is on right). That takes care of water-now to find out if the plastic impairs the sunlight getting in.I called one of the big Arizona stores and they did not have an opinion about the diagonal reflectivity of the plastic vs the " bumpy" glass factory panel.. I think the thing will be fine when the sunn is high in sky but when low like at morning the plastic cover may reduce the "gain". Today at noon first test I was getting 440 watts at noon with a 580 watt setup thats Ohio on a clear sunny but not the brightest day. Seems about similar to your panels as you are farther south a bit. there are websites that help you figure how many degrees.

 

[HackNFly]

Well I am not sure but I think the watts do not double in series, just the volts.......I think. Someone please correct if necessary. If I am correct then 300 watts is very good for a 335 watt panel in May not facing the sun directly.
Also I think that like everything else the max ratings are in near perfect conditions whatever that might be.
That being said. Yesterday while adding four more panels on our roof i cracked one with a stray screw (sigh). Tested and had same specs stillso I installed in the group. Thought about what to fill in the glass cracks because rain would do something bad soon enough .I decided that a repaired panel lasting a long time was better than a broken panel at 100 % but dying in a few months either optically or electronically, I cut a tight fitting piece of 1/8"thick plexiglass and silicone sealed it in place with only the frame not the glass getting the sealant. (see picture- fixed one is on right). That takes care of water-now to find out if the plastic impairs the sunlight getting in.I called one of the big Arizona stores and they did not have an opinion about the diagonal reflectivity of the plastic vs the " bumpy" glass factory panel.. I think the thing will be fine when the sunn is high in sky but when low like at morning the plastic cover may reduce the "gain". Today at noon first test I was getting 440 watts at noon with a 580 watt setup thats Ohio on a clear sunny but not the brightest day. Seems about similar to your panels as you are farther south a bit. there are websites that help you figure how many degrees.

Thanks for the reply. Watts = V*A. When you connect in series, the amps stay the same and the volts double. If you connect in parallel the amps double and the voltage stays the same. However if you connect 2 335 watt panels you should get 670 watts total in ideal conditions.

I like your fix for your solar panels. I was looking for all types of fixes, I ended up using
Rustoleum 2X crystal clear

As seen in this video:

It was one of the few ones that had any follow up, flex seal supposedly worked too but took longer to apply. I was trying to go cheap, if I can get the panels working right then the whole set up will pay itself off after 8 years. At which point I can buy other panels if these start to fail.

Where did you get your acrylic sheet? I checked home depot and for my size panels, 72 X 40, it would be over $100.

 

[HackNFly]

Next time you test, add a load > what your panels can produce.

I forgot to mention that, I tried connecting my space heater to my inverter and I saw that it was pulling power from my battery by using my BMS, total power output only went up by like 10 watts when trying that.

 

[sunshine_eggo]

Good. #1 cause of what you describe is the battery/charge controller being at the absorption voltage, and it just won't take any more.

Did you try them in parallel?

If one is underperforming on current the other will be limited to that current when they are in series. In parallel, they will deliver whatever current they can, and you might see more. Also worth checking them individually.

A clamp DC ammeter is very helpful when trying to figure things like this out.

Additionally, recommend you set bulk/absorp to 28.4V and float to 27.2V.

 

[HackNFly]

Good. #1 cause of what you describe is the battery/charge controller being at the absorption voltage, and it just won't take any more.

Did you try them in parallel?

If one is underperforming on current the other will be limited to that current when they are in series. In parallel, they will deliver whatever current they can, and you might see more. Also worth checking them individually.

A clamp DC ammeter is very helpful when trying to figure things like this out.

Additionally, recommend you set bulk/absorp to 28.4V and float to 27.2V.

Thanks, I haven't tried them in parallel. I figured the voltage would be too low to be useful, but the MPPT input voltage range is 30 -145 so I will try the panels individually tomorrow.

I'm also going to order a cheap lux meter, I found a paper

https://www.she-inc.org/wp-content/uploads/2018/04/TR-17-A-low-cost-method-of-measuring-solar-irradiance.pdf

that showed how to convert from lux to w/m2. Based on some of the feedback I've gotten I think it just isn't a 1000w/m2 day and my expectations were too high.

 

[kanelr]

Good. #1 cause of what you describe is the battery/charge controller being at the absorption voltage, and it just won't take any more.

Did you try them in parallel?

If one is underperforming on current the other will be limited to that current when they are in series. In parallel, they will deliver whatever current they can, and you might see more. Also worth checking them individually.

A clamp DC ammeter is very helpful when trying to figure things like this out.

Additionally, recommend you set bulk/absorp to 28.4V and float to 27.2V.

I was thinking that even just putting a spst panel mount toggle through the black box on back of the repaired panel so you could disconnect that one panel to see of the output drops the "full amount" expected. Team plastics on w140 in cleve is competitive .I would only cover one panel at at time the seal at the aluminum silicone bond is pretty critical for water.