Used Solar Panels

[Netsua]

I have a barn I’ve wanted to put solar on. It already has a battery bank, inverter, and generator. Being an accessory structure, I never wanted to spend a ton.

Ran across a BUNCH of used panels. Buyer claims to have purchased them 5 years ago, but only used them for 3.

The panel is still sold today for 275-290 per panel. What would you think the per panel value of these would be?

Should only be about 5% degraded right?

 

[BobR]

Check out the prices of used panels here. (I am not affiliated with this company): https://store.santansolar.com/product-category/solar-panels/

 

[chrisski]

I can’t say how much they’ve degraded, but I recommend you find out what your power requirements are and build from there.

A couple mistakes I made was getting my first panel off a good deal, and then a lot of work to find matching panels to make the system bigger. The next thing was not planning the build enough, which lead to three different banks of panels and three solar charge controllers.

In my area, I can make twice the wattage of the panels per day in watt hours in the winter, and in the summer that grows to six times.

So, I can make about 2600 wh - 7800 wh depending on the time of year. I just recommend you do calculations off what you Need to avoid not just the cost, but building two or three systems to get the power you need.

 

[Bluedog225]

Looks around for how to test used panels individually. And for “relabeling” or covering up the old label to hide that they are recalled Trinas. And be ready to take a loss if they are junk. New panels are cheap (Ish).

 

[Netsua]

Looks around for how to test used panels individually. And for “relabeling” or covering up the old label to hide that they are recalled Trinas. And be ready to take a loss if they are junk. New panels are cheap (Ish).

Holy moly! Thank you so much! I looked up these Trina recall panels - and without question that’s exactly what these panels are!

 

[Netsua]

Check out the prices of used panels here. (I am not affiliated with this company): https://store.santansolar.com/product-category/solar-panels/

Will check it out - thank you

 

[Netsua]

I can’t say how much they’ve degraded, but I recommend you find out what your power requirements are and build from there.

A couple mistakes I made was getting my first panel off a good deal, and then a lot of work to find matching panels to make the system bigger. The next thing was not planning the build enough, which lead to three different banks of panels and three solar charge controllers.

In my area, I can make twice the wattage of the panels per day in watt hours in the winter, and in the summer that grows to six times.

So, I can make about 2600 wh - 7800 wh depending on the time of year. I just recommend you do calculations off what you Need to avoid not just the cost, but building two or three systems to get the power you need.

Thanks for the input. Thankfully this is just for my barn. I’m getting by right now with a 450ah bank and a generator for running tools/charging - so really anything extra is only helpful. Just not wanting to spend a ton.

 

[chrisski]

If you already have that stuff figured out and a battery, all downhill from there.

I’ve found in Arizona with my battery bank about your size, 950 watts of panels charged the bank year round. Done by noon except on cloudy days and I use between 80 ah and 165 ah.

 

[HRTKD]

If shipping is involved, then it may not be the bargain you think it is. I bought new 320 watt panels locally for $185 each and was happy to find them.

 

[Kornbread]

Trina panels ... easy enough to check for snail trails or cracked vinyl.

 

[fafrd]

Holy moly! Thank you so much! I looked up these Trina recall panels - and without question that’s exactly what these panels are!

Used panels often are not nearly the bargain they appear to be.

-unknown age / power degradation (so higher effective $/W)

-unknown history (and often panels that were recalled due to quality issue, as you’ve discovered)

-usually lower power than new panels, meaning $/W cost for racking (which is about $40/ panel, regardless of size) will be higher

-no warranty

I’m lucky I live in near a major solar wholesaler where I can pick up panels myself to avoid shipping charges.

By monitoring their pricing, they almost have a sale on panels they are closing out every couple months or so.

My last purchase was new 380W half-cut panels for $0.39/W, so if you are in the right place and patient, you can often find premium new panels for close-to-used-panel prices (all-in, including cost of racking).

Installers will also often have leftover panels after a big install which they sell at bargain prices on Craigslist. These often carry a full warranty as well (supposedly, I’ve never actually pulled the trigger on one of those Craigslist deals before…).

 

[fafrd]

Trina panels ... easy enough to check for snail trails or cracked vinyl.

Meaning they can be a deal or they should be avoided at all cost?

 

[Kornbread]

Meaning they can be a deal or they should be avoided at all cost?

Either. Used panels can be a good deal, or not. They can (SanTan's inventory is in perpetual motion) be bought for $.14/watt. I got no problem with buying panels with known issues for super cheap, if they fit the need. This includes cracked vinyl or snail trails. Although, their seems to be differing opinions on the viability of panels with snail trails, I'd wager cracked vinyl will lead to an untimely panel death. In certain situations, like an off grid hunting cabin, they could fit the need. Not going to use them on the house or grid tied. In the OP's situation, on a barn and not wanting to spend a lot of $, they may work just fine.

 

[fafrd]

Either. Used panels can be a good deal, or not. They can (SanTan's inventory is in perpetual motion) be bought for $.14/watt. I got no problem with buying panels with known issues for super cheap, if they fit the need. This includes cracked vinyl or snail trails. Although, their seems to be differing opinions on the viability of panels with snail trails, I'd wager cracked vinyl will lead to an untimely panel death. In certain situations, like an off grid hunting cabin, they could fit the need. Not going to use them on the house or grid tied. In the OP's situation, on a barn and not wanting to spend a lot of $, they may work just fine.

‘Cracked vinyl’ I understand and agree they are likely to lead to premature death of the panel, but what exactly are ‘snail trails’?

I have to admit I thought they were merely a cosmetic issue when I saw the description on Santan’s website, but you are making it sound as ‘snail trails’ may actually as big of a reliability concern as cracked vinyl…

Would like to learn more if you’ve got any pointers…

 

[HRTKD]

‘Cracked vinyl’ I understand and agree they are likely to lead to premature death of the panel, but what exactly are ‘snail trails’?

I have to admit I thought they were merely a cosmetic issue when I saw the description on Santan’s website, but you are making it sound as ‘snail trails’ may actually as big of a reliability concern as cracked vinyl…

Would like to learn more if you’ve got any pointers…

A decent write-up on "snail trails":

Snail Trails on Solar Panels– an aesthetic issue or a performance limiter?

What are snail Trails: Snail trails are discolouration of the panel, which usually builds up over couple of years of power production on the

www.avisolar.com

 

[sunshine]

I have to admit I thought they were merely a cosmetic issue when I saw the description on Santan’s website, but you are making it sound as ‘snail trails’ may actually as big of a reliability concern as cracked vinyl…

These are not as large a problem when running at low voltages rather than in longer high voltage strings.

However, even when looking at panels for my 12v conversions any imperfections to the 'power' region are the first reason for rejection. Just not worth it at this price level as other better alternatives available.

I allow some latitude for vinyl damage caused during or after removal

 

[fafrd]

A decent write-up on "snail trails":

Snail Trails on Solar Panels– an aesthetic issue or a performance limiter?

What are snail Trails: Snail trails are discolouration of the panel, which usually builds up over couple of years of power production on the

www.avisolar.com

Great - thanks.

No ‘snail trail’ panels for me. All of this solar stuff is complicated enough without needing to add yet more thing to stress out over (and perform occasional inspections for).

 

[fafrd]

These are not as large a problem when running at low voltages rather than in longer high voltage strings.

However, even when looking at panels for my 12v conversions any imperfections to the 'power' region are the first reason for rejection. Just not worth it at this price level as other better alternatives available.

I allow some latitude for vinyl damage caused during or after removal

Are you saying that snail trails are only likely to cause a problem in high-voltage strings or that they are only likely to form in the first place m high-voltage strings?

And what string voltage levels are we talking about?

Are the formation of snail trails understood to be only the result of a manufacturing defect like microcracks or can any properly-manufactured panel develop snail trails (especially if operated within a high-enough voltage string?

All of my purchased-new panels are currently operating at 1S voltages of 35-40V (microinverters & parallel strings) so presumably I’ve got nothing to worry about, but I’ve been mulling some hybrid inverters that require string voltages of 250V or even 500V.

Are string voltages at that level the kind of ‘high voltages’ that can cause snail trails to develop in otherwise defect-free panels or is there nothing to worry about at these voltage levels (unless using panels that have already developed snail trails)?

 

[sunshine]

Are string voltages at that level the kind of ‘high voltages’ that can cause snail trails to develop in otherwise defect-free panels or is there nothing to worry about at these voltage levels (unless using panels that have already developed snail trails)?

I only use 2nd hand panels for low voltage.
Looking at the burn marks through the vinyl backing on many of the used PV I've seen I would be very wary of using any in a string unless sure of their integrity and even then make allowances in case of failure. Even new ones should be installed where failure won't cause disaster.

I guess snail trails could occur @ 0V wherever moisture can get in, or other reactive material in manufacturing can breakdown. But the extent and. problems caused will no doubt increase with voltage.

There is nothing to damage behind my panels so am unconcerned by any defects appearing until I notice a drop in power.

The main point is 2nd hand panels, even with minor defects are great. However, even with the recent price increases, there may not be the savings in used panels over new in anything other than back yard dyi!

 

[Hedges]

I tried testing panels, after I determined some must be underperforming.
Voc/Isc only flagged some bad panels. Vmp/Imp (or rather Vload/I load with a resistive load) was needed to see others.
Using an IR camera showed individual hot cells while an array was operating with an MPPT (Haven't determined if short circuit testing would produce such an image.)

Measuring PV panel performance

I suppose I could buy a solar panel tester like Will reviewed, but that doesn't feel DIY enough to me. Besides, I'm a cheapskate, and I try to do things in the most difficult (and expensive if the equipment wasn't on hand) way. I'm presently working on an underperforming string of Sharp 165W...

diysolarforum.com

PV panels are relatively cheap in comparison to balance of system, so I pay extra for brands known for quality.