Working Thread for Solar Beginner Post/FAQ

BB. · October 2012

Re: Working Thread for Solar Beginner Post/FAQ

Some threads about Lithium and other rechargeable battery chemistries:

Pros & Cons of Lithium-ion batteries for solar application
Charge Controller for LiFePO4 Batteries
Compare Nickel-Iron Edison Batteries and Chinese Ni-Fe Cells
New Lithium Ion battery for us?
Lithium Phosphate Batteries
Would you consider a Lithium Ion battery?
Lithium-Ion charging with solarpanel

As always, you can use Google Search on the forum by using the "site:wind-sun.com" tag to limit searches to our forum:

Lithium site:wind-sun.com
Lithium site:https://forum.solar-electric.com

now: Lithium site:forum.solar-electric.com

-Bill

PS: add on 6/22/2014--And leave in the warning that there are many different Li-Ion chemistries out there--And using the wrong charging algorithms/voltages can destroy your battery pack (or worse):

PNjunction wrote: »

Wow - no offense, but this is pivotal and I have to use all caps:

DO NOT FOLLOW THE VOLTAGES LISTED IN THAT LINK FOR YOUR LIFEPO'4S - THEY ARE FOR A DIFFERENT LI-ION CHEMISTRY

Once again, I'll point out a great REAL-WORLD thread that describes in great detail how to do it with the chemistry we ARE using:

http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html

I can see that this has quickly devolved into a technical p*ssing match between real-world hands on, vs someone who doesn't actually own a bank of his own. Until you have one, all we'll end up doing is throwing links at each other, which does lurkers no good.

It is for this very reason, that most real-world users try to avoid armchair-engineering squabbles and eventually go silent. Although that might be to the relief of the crowd.

4/22/2020: McGivor recommends this site as a good source for Li Ion battery information/confuguration/usage:

mcgivor said:

mcgivor said:
@OffGridMarty This site http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/ which is devoted to marine applications though the fundementals remain the same, I found to be very helpful when I began, it contains most of the information needed, well worth reading.

BB. · June 2013

Re: Working Thread for Solar Beginner Post/FAQ

We have a fair number or requests about repairing older Xantrex (and others) AC inverters. Here is (or are) some options:

offgrid me wrote: »

For anybody that has a problem with an older Trace SW/SW+ or DR-series, contact this guy using his web form on his site:
http://www.phantompowerservices.com/

He'll get it working again.
--
Chris
I think this is the one
Ned

-Bill

PS: As of 10/10/2013:

Below is a list of companies that can repair the old Trace inverters.

I suggest Sunpumps.

INVERTER REPAIR

-Sunpumps (Rod)
800-370-8115

-Tekris (Brian)
877-483-5747

-RVMD (Steve)
520-270-9922

Old black trace inverters
Craig Wilburn
425-501-7280

David Lauzon
President
Northern Arizona Wind and Sun

Link to post where you may find updates to list:

Where to repair old Trace/Xantrex Inverters...

PPS: 1/5/2013:

Blackcherry04 wrote: »

Here are the parts you need, only you know if they are cost effective.

http://inverterservicecenter.com/Inverters/Inverter-Repair-Parts/Xantrex-Repair-Parts/SW-5548

The problem is buying components is you don't know what the problem is and if one thing went bad what else did it take out. You buy it on a one way trip, if it's doesn't work you eat the cost. I'll take a new one with a warranty and sleep better.

4/15/2014 (some people that make repairs--PM them for further information--For information only):

greensolarelectric wrote: »

I repair/refurbish SMA Grid tie inverters. I offer a 6 month warranty on all repaired inverters. And i offer a 1 year warranty for a additional $50

Most repairs cost from $200-$600.

Thanks,

Greensolarelectric
http://www.greensolarelectric.com/Inverterrepair.html

jclothi wrote: »

Ray
How did your situation work out, regarding the failed swr 2500? Did you find a repair service?
If not, I can help you. I am retired but I will help people (only) that are financially squeezed (and screwed by sma!) and simply will be unable to get back on line, otherwise. Why cant they understand that there is good will to be had in providing support? Anyone with your experience may be expected to never buy another sma product, huh!
jclothi -at- attglobal.net

Compuhans wrote: »

I have been repairing various solar inverters for people who had a inverter go bad that is out of warranty, usually they can be restored to where years of life are added to the unit.
I fix Sunnyboy 1800 2100 2500 3000 4000, Xantrex , Power One Aurora and PV powered ( and likely others if they came across my workbench)
Only in case of catastrophic burnout do I tell them to throw them out.

1/15/2018--Dean posted in another thread that he repairs inverters too:

SolarWizard said
Contact Dean at abneysolarelectrix.com for SW & SW+ repair and testing, Oldest Trace repair center in the NW.

5/19/2022:

bnes` said:

There are a few individuals still repairing the old SMA units, and good for them. I had luck with

707-621-5107
info@greensolarelectric.com
Covelo, CA 95428

littleharbor2 said:
Compuhans on eBay repairs and sells older Sunny Boy inverters. He is located in Agoura Hills (Southern Calif.)

niel · June 2013

Re: Working Thread for Solar Beginner Post/FAQ

of course this is not an endorsement or recommendation of anybodies service as naws and ourselves as moderators for naws are not of 1st hand knowledge of anyone and we are not in that aspect of the business as far as i know so this is a disclaimer.

BB. · April 2014

Re: Working Thread for Solar Beginner Post/FAQ

Some early 1960's videos that Verdigo found:

verdigo wrote: »

I found these old DOD videos on YouTube . I'm pretty sure I seen these in my Army days, and thought they might be useful for some here.

https://www.youtube.com/watch?v=DjYePMNOQXw [How AC Generators and Motors Work]

https://www.youtube.com/watch?v=MXQzUhORgKM [How DC Generators Work]

-Bill

BB. · September 2014

Re: Working Thread for Solar Beginner Post/FAQ

Poster Les Nagy has a thread suggesting various volt meters:

Which mulitmeter? My opinion for those looking for something reliable

-Bill

PNjunction · October 2014

Re: Working Thread for Solar Beginner Post/FAQ

LiFePo4 warning for beginners!

Unless you are extremely astute or have prior experience, I would NOT generally recommend a beginner immediately go with lifepo4 - you have enough going on already with other factors to fill your head.

The biggest issue in order not to absolutely blow your solar budget right off the bat, is not knowing your power needs FIRST. If you don't, you may end up with a totally inappropriately sized lifepo4 battery, or worse yet, be tempted to buy lower priced CRAP. Please don't do that. I would much rather have a total beginner spend their budget properly on a lead-based system, and then graduate to lifepo4 when / if they are ready.

It is for this reason that we suggest beginners start with lower-priced, yet still somewhat quality lead-acid batteries as a "learner" bank. I think it would be irresponsible to recommend something like a Rolls-Surrette to an absolute beginner who may not be up to the task of proper maintenance, and likewise, suggest a jump into lifepo4 without having the background in figuring out your power needs, solar insolation, and other hardware infrastructure matching first.

Up-front costs of lifepo4 are high, and making a mistake here can leave you stranded with a battery with nowhere to go, and possibly nobody who wants to buy one used from you.

I love lifepo4, but I'm just trying to keep it real.

BB. · January 2016

Some more Lead Acid Battery answers from an older 2012 thread:

http://forum.solar-electric.com/discussion/comment/181142/#Comment_181142

"Equalization" is "over charging" a battery (or some cells in a battery) to bring "low specific gravity" cells back up to their maximum SG (hopefully, SG between high and low cell is less than 0.030 or 0.015 s.g.).

Normally that is done when a battery is already at "full charge" and you are overcharging the fully charged cells to bring up any low cells. Then equalization should end.

By the way, how often do you need to refill the cells? More or less, ~2 months is "good"... More often, may be over charging. Much less often, may be under charging (although, the Trojan RE batteries have been reported by one or two posters here as using significantly less water than their non-RE Trojans).

At this point, deep cycling (to ~50% or so State of Charge, as suggested by Vic) to try and knock/converter any sulfation that may be covering the plates is probably your best bet. It may take 10-20 cycles before you see full improvement (if any).

As Windsun asked, did the batteries sit for months without any charging? That will cause sulfation to form "before its time".

Where the batteries stored at high temperatures? Typically, every 10C/18F over ~25C/77F causes batteries to age by a factor of 2x (36F over 77F, would be 2*2=4x faster). Also "hot batteries" have faster self discharge.

I ran across this page on why different types of batteries have different starting s.g. fills... Is pretty interesting:

Specific Gravity vs Applications
1.285 Heavily cycled batteries such as for forklifts (traction).
1.260 Automotive (SLI)
1.250 UPS – Standby with high momentary discharge current requirement.
1.215 Geral applications such as power utility and telephone.

As mentioned earlier, the specific gravity (spgr.) of a fully charged industrial battery, or traction battery, is generally 1.285, depending on the manufacturer and type. Some manufacturers use specific gravities as high as 1.320 in an attempt to gain additional Ah capacity, but at the cost of a shorter cycle life.

...

Higher Gravity = vs Lower Gravity =
More capacity / Less capacity
Shorter life / Longer life
Higher momentary discharge rates / Lower momentary discharge rates
Less adaptable to "floating: operation / More adaptable to "floating" operation
More standing loss / Less standing loss

At 77F, the equation that relates S.G. to battery cell voltage is:

Specific gravity = single-cell open-circuit voltage - 0.845 (example: 2.13v – 0.845 = 1.285)
Or
Single-cell open circuit voltage = specific gravity + 0.845.

Or, for your bank:

Battery "resting voltage" = 6 cells x (1.245+0.845) = 12.54 volts

So, your resting voltage seems to relate to the S.G. pretty closely (assuming battery bank is around ~77F).

At this point, it sure sounds like your batteries are sulfated (low S.G.) and, at this time, there are no "accepted" methods to convert hardened (crystallized) Lead Sulfate back to Lead + free sulfur (back to acid).

Cycling the battery bank (shed material and leave fresh lead exposed) is one solution (by the way, over charging/equalization generates O2 which can corrode the Positive Plate Frame and oxidize the lead (from what little I understand), it is possible to cycle discharge/recharge to drive the Oxygen from the lead plate (but not the frame).

There are "Desulfators" and people that love them or hate them (a couple such conversations here have resulted in, rare for us, locked/deleted threads). On the positive side, a desufator should not damage a battery bank (that is, otherwise, kept properly charged). On the down side, a poster here has seen a desulfator confuse his Outback MPPT charge controller and dramatically reduce the charge controller's battery charging current.

And lastly, there are the magic battery additives. Some contain Cadmium (which is a heavy metal that can cause battery recyclers to charge you to dispose of a battery bank)--And has some validity for use with Lead Acid battery chemistry. Epsom Salt variants and even oils -- Which appear to have less validity.

Not many folks here will tell you to try desulfators/additives... But there are the occasional (apparently) positive results.

Perhaps some others here with much more battery experience/knowledge than I--Can give you some better guidance.

-Bill

BB. · May 2016

This link is a "Generator" link--But it explains pretty much all you need to know about about basic AC power systems, pure sine wave, modified square wave, etc.:

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

Thank you Mike for bringing this site up again:

mike95490 said:

The lighting & grip website has been revamped, but I found the generator page. It's basically talking about cheap inverter generators having square and mod sine output, and that even PSW inverter and conventional generators, seeing strangely reactive loads instead of "old style" restive loads, are unable to provide sine waves and the loading distorts the waveform (much as I have experienced with my new small robin/subaru/hatz genset) it's very interesting and should be required reading.
http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorSquare Wave Generators

-Bill

BB. · April 2018

An older thread about why we suggest matching Solar panel Vmp ratings within 5-10% for parallel connections, and Imp to within 5-10% for series connections:

http://forum.solar-electric.com/discussion/5458/two-strings-in-parallel-with-unequal-string-voltages

-Bill

PS: Dec 17, 2018:

Add a link to David Angelini's Post about why mixing panels and array directions with a single MPPT controller can be an issue (article is written towards comparing central GT inverters and micro-GT inverters)--But does discuss MPPT issues:

https://forum.solar-electric.com/discussion/comment/393434#Comment_393434

Dave Angelini said:
The arrays harvest need good static mpv and dynamic. There are plenty of cases where one controller fails to do this right. The article below was from 2010 when we were field testing the first 600v mppt. The shade tolerant feature was pretty amazing and it worked well in moving clouds.

https://us.v-cdn.net/6024911/uploads/editor/37/fpqzmxmhly43.pdf

BB. · May 2018

Here is a nice discussion about how to pick the proper fuse(s) and circuit breaker(s) for your DC power system:

http://forum.solar-electric.com/discussion/353232/oversized-wire-and-breaker

-Bill

BB. · November 2018

Plumbing and Water tank forum (and other stuff) by one of our own posters:

cow_rancher said:
mike95490 said:

I seasonally get iron in my water, and need to remove it before the main filtering.
jonr said:
You can oxidize (various chemicals or ozone or air) and then let it settle out in a holding tank.
As jonr said, oxidation is the usual method i.e. bubblier in a storage tank with a pressure tank beyond that...
"Main Filtering" what are you filtering out, whole house filters are normally not needed, they reduce the flow too much, and require maintenance.
This is a Solar site so I see no conflict in sending you to another site https://pumpsandtanks.com/index.php , good unbiased experts there unlike another well known plumbing site, Speedbump is our resident expert and I own the site and won't try to sell you anything, besides I have nothing to sell.

Rancher

-Bill

BB. · December 2018

Poster Graham Parkinson has posted information about a really neat (smaller) LED UVC water disinfection unit:

https://forum.solar-electric.com/discussion/comment/393302#Comment_393302

Graham Parkinson said:
Regarding UV LED disinfection:
My dear Alma Mater, University of British Columbia, Physics Department has spun off a startup company called Acuva that markets 250-280 UV Led water treatment systems. Several of our off grid neighbours have also purchased these high quality, efficient units and we can recommend them:
www.acuvatech.com
Advantages over traditional fluorescent tube UV sources include instant startup (using flow sensors), long life (no changing tubes every year) no need for solenoid flow interlocks to prevent untreated water flow during warmup, low standby draw (mA).
If you use these units, that would reduce your need to expand your solar system!

-Bill

cow_rancher · December 2018

Who sells them?

Rancher

BB. · December 2018

I will post this for a bit--$100 off if you use their discount code in the next couple days.

Also, the RV Geeks has an install video and a test result video using contaminated samples:

http://www.thervgeeks.com/plumbing/acuva-giveaway/

At this point in time, it looks like you purchase direct from the Mfg's website. www.acuvatech.com

-Bill

BB. · August 2019

Advice on getting long(er) life from your AGM batteries. Marc Kurth, who sells and services AGM batteries (and other equipment):

https://forum.solar-electric.com/discussion/comment/401301#Comment_401301

...

First: I will categorically state that almost every early Concorde battery failure that we see is from undercharging. Undercharging is the enemy and always has been forever. Undercharging can include too low of an Absorb voltage, too short of an Absorb time, too low of a charge rate and not reaching 100% SOC often enough. Way behind undercharging on the list is high temperature. Overcharging is rare to the point of being almost non-existent.

Second: It is MY opinion that Concorde has gradually ratcheted up their support of “conditioning” because customers are so afraid of “over charging” their batteries, that they undercharge them. MOST people do not read (or perhaps ignore) the fact that Concorde batteries must be charged at the Absorb voltage until they are only drawing one half of one percent of the battery bank C/20 rating. Simply put, 0.50 amps per 100 AH of battery capacity.

Dropping to Float before reaching this point is a form of undercharging and will cause sulfation. Their manual also provides suggested Absorb time settings to be used as a starting point to fine tune. Two hours is minimum for very shallow cycling and four hours for deeper cycling. Remember that “end amps” is the key and that lots of Float time brings strings into balance. We often read the internet megaphone about overcharging AGM’s. Think about a typical 1200 ah bank. At 100% SOC, the entire group of 24 batteries is only drawing 6 amps! I assure you that it will take a very long time to cook them. Especially when the sun goes down with great regularity.

There is much, much more to discuss, but I will say that if our battery banks are charged per the manufacturer’s instructions, equalizing is not required for the first 5-7 years. Yes, it is a slightly destructive process, but less so than sulfation!

OK that was wordy! But go ahead tell me what I missed!

Thank you Marc!

-Bill

PS: Add CoachDad's issues with AGM and charging issues:

I found the thread where CoachDad had issues with the rolling battery manual revisions (for Concorde Lifeline batteries):

https://forum.solar-electric.com/discussion/354712/time-to-change-batteries

BB. · November 2019

Member Blackda3 has had a good experience with this soft start kit for RV A/C + a (relatively small) Honda eu2000i (1,800 Watt) genset

Blackda3 said:

I had a similar situation in 2017. My 2017 Aliner came with the Dometic 10.15k BTU Cool Cat air conditioner/heat pump. Dometic states that the locked rotation amps is 50.0 amps AC (120v). Running the Cool Cat required two Honda 2000 generators in parallel. I was able to measure the actual amp load over 3 test runs as requiring: Approx. 2 amps to start running the fan for about 30 seconds; then the compressor would start/surge to 44.1 amps (approx. 5300 watts peak for about 0.5 seconds); and then taper off to about 9 amps for the rest of the cycle. It would then drop to 2 amps on fan only until another cycle begins. My solution was a smart/soft start capacitor from MicroAir.net. I had it installed by my local RV shop (good thing too since the directions for my unit were wrong). It allows me to run my A/C with a single Honda 2000. It doesn't start as quickly but ramps up within 45-60 seconds. I wish I had know about this solution then - it would have saved me buying a second generator that I no longer need.

I assume this is the unit he used:

https://www.microair.net/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners?variant=30176048267

Note the above unit only works on 120 VAC, and needs a modification to run on 230 VAC.

-Bill

BB. · December 2020

Member @Mcgivor recommends this site for folks getting started in Li Ion (specifically LiFePO4 -- Lithium Iron Phosphate):

http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank

From this post:

https://forum.solar-electric.com/discussion/comment/414092#Comment_414092

mcgivor said:
Can't say for sure but it would appear that the cell is damaged if the voltage reading is zero, have you checked the meter on the other cells to prove it's working?

One of the fundamental cautions when parallel connecting a number of cells is to ensure the voltage of all cells are within 0.005V (5mV) it is important to have a meter capable of measuring millivolts as 0.01V is not acceptable, meters will have a certain error some as much as 5-10% and that could represent a large difference in state of charge, When this caution is ignored the result is the balance of the cells will dump massive amounts of current, perhaps thousands of amps, into a single cell if it's state of charge is lower, which has the potential to cause a dangerous situation, or at very least just ruin the cell.

Take the time to study extensively from sources other than You Tube, the video linked has misinformation not to mention bad practice, this link http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/ is a good place to start but don't limit your education to a single source.

-Bill

BB. · April 2021

Many years ago, there was some Q&A about the NEC usage of ganged circuit breakers/1 amp ground fault fuse detection to address Arc-Fault failures in solar array wiring (sustained arcing between two wires, two connectors, wire to earth ground).

I dissagreed with this implementation (essensially puts a 1 amp breaker/fuse between DC solar/battery bus negative bus and green wire (equipment/ground rod/etc.) safety ground. The fuse or breaker tripping, causes the solar charge controller to shutdown (there are many different implementations of this specific function).

In no UL/NRTL (nationally recognized testing laboratory) is a fuse between power return and safety ground ever allowed... Except in solar.

The white paper addressed the implementation of a ganged breaker with 1 amp breaker between DC return and safety ground which trips the other two +&- solar power connections. And how the tripping of a fuse/breaker in the safety ground bond makes the solar power system (DC Bus Side) increadibly unsafe... Anyway, I was ignored by the powers that be... Here are the present working links to the paper and the disucssion (note that Vic just asked the question again today--Please use Vic's discussion if anyone wants further discussions--The FAQ is not a great place to have "the discussion":

https://forum.solar-electric.com/discussion/356660/ground-fault-white-paper-by-bb-bill#latest

Hi Vic,

Really want to "dig that one up" again?

The paper is here:

https://us.v-cdn.net/6024911/uploads/attachments/512/1965.pdf

Note--Right after I made that PDF, my computer's hard drive crashed... I did not bother to resurrect the document as it pretty said everything I wanted to say--And while I had a few engineers from other companies at the time contact me, the powers that be said I was talking about European regulations (not).

Our Forum discussion:

https://forum.solar-electric.com/discussion/9345/system-grounding

Midnite Forum Discussion:

http://midniteftp.com/forum/index.php?topic=142.0

Both sites have had hosting/URL changes (and Midnite users now manage the Midnite forum, not Midnite itself--I think).

-Bill

BB. · July 2021

Some old threads with "extreme" off grid systems (the good and the bad) and a smaller GT system with unsafe solar panels:

What "can be done":
https://forum.solar-electric.com/discussion/19312/extreme-off-grid

What "can go wrong" with large/complex off grid power system:
https://forum.solar-electric.com/discussion/17986/is-the-system-set-up-right/p1

What can "really go wrong" (grid tied home system--not large):

Panel Fire Question

-Bill

BB. · May 2022

Discussion on "How Solar Panels Work" electrically (series/parallel connections. Sizing array to controller, mixing panels, etc.):

https://forum.solar-electric.com/discussion/5458/two-strings-in-parallel-with-unequal-string-voltages

-Bill

Dave Angelini · May 2022

You-tube on comparing the Sol Arc solid state all in one to the 80 pound Toroid XFMR based XW pro by Dean Abney in high power modes.

https://www.youtube.com/watch?v=-Ez4cbuy7IQ

Photowhit · May 2022

If I'm listening correctly, it's amazing the XW design on the schneider goes back to Trace/Xantrex, which would mean boB and Robin Gugel...

So I'm even more impressed with my High frequency (Xantrex)Prosine 1800, which is a High frequency inverter which regularly (8 years), wonder how different the design is between the High frequency inverters of the 2000's and the high frequency of today are? I ran my water heater at 900watts along with the fridge, window air conditioner and assorted little loads laptop, lights, fan...

Dave Angelini · May 2022

I remember the Engineer Jeff Everette at Xantrex when the XW was announced of the Xantrex Forum. Bob was at Outback then. He can fill in the blanks. I remember Jeff writing to him on the forum about what XW meant to the design team.

Xantrex Wins. They had huge Dod grants that helped them build what I still think is the best out there now 16 years later. Just the way they filter/cool the air and channel it to keep dust off the components is a classic engineering move when cost is not an issue. I got to work with Jeff on the first networked MPPT field testing offgrid. I think he is in the LFP business now.

Your running Photowhit 120VAC? The big issue with HF inverters is split phase operation. It is the reason that they have to build large outputs to keep them from faulting and shutting down power with pretty normal household loads. Dean went thru that in the video and remarked that it would be a pain to lose power offgrid and have to walk out and reset the Inverter.

The only time we have ever lost power was when I was testing for Schneider and they provided a second XW for AC bypass back-up to the unit under test.

I mean zero times losing power on XW in 16 years !

Photowhit · May 2022

Yes, all 120, still am with the 120 version on the Magnum 4024...

I'm always amazed at the small group of people involved in so much of early solar electric and off grid design.

Back to Heart Akerson not being happy with square wave inverters on his sailboat and designing and building early sinewave inverter, selling out and going sailing and rejoining to build an all-in-one transverter to accept all sorts of input and producing assorted output. Not sure where that stands, they got UL approval, but the max DC was 40V or less... I think he had some health problems...

The Pot farmers supporting much of the land based and boating supporting much of the rest...

I caught an interest in my late 20's, and was amazed that we had a solar electric store in Tallahassee in the late 80's! While Al Simpler was doing some installs on islands off the coast of Florida, he had contracts setting up schools, clinics, hospitals in the Caribbean and Africa from the late 70's.

Dave Angelini · May 2022

Health problems are pretty common in this group. We used a Heart on our boat until Trace started building something far more relaible.

Not to knock him as he was as you said, a pioneer. You would see people in airports all over the world struggling to carry a carry-on that was a Heart inverter/charger

Back for a repair, and they could do that then reliably.

Fond memories of Florida and the year we tried to live there on a sailboat. By the mid 90's it had changed so much we went back to Mexico. Take Care !

BB. · December 2022

New member TheAppleTreeGuy did some research and found the Model/Part numbers of Sunpower solar panels that require "Positive Grounded Panels" in solar applications. PGR panels are from around 15 years ago (2008 +/-) and they have a loss of output power if connected to negative grounded power systems/GT inverters.

This thread has some historical links too to white papers about the issue too.

https://forum.solar-electric.com/discussion/357711/positive-ground-sunpower-327-watt-t5-solar-panels

Image: https://us.v-cdn.net/6024911/uploads/editor/62/ful0qp2gyb1l.png

Thank you again TheAppleTreeGuy for your research and posting that information here. As these panels (possibly) work their way into the used market--I am sure that this will be very helpful to people considering using these older panels.

-Bill

Working Thread for Solar Beginner Post/FAQ

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