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groingo
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# Posted: 20 Aug 2025 02:54pm - Edited by: groingo
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Not being one to see something useful just do nothing I put the old 6 Renogy 100 watt panels back to work and got some pleasing results.
First, they look old, 2 BB, snail trails all over the place
and overall under the glass kinda gungy.
So, I plugged them into my new 8 awg wire onto my new Shengen MTTP (undersized 20 amp) charge controller and was blown away how well they performed, easily pulling 19.7 amps at 20.4 volts where all the time prior regardless the controller never higher than 13 amps at best! These numbers were also limited due to the 20 amp controller and the battery now being full charged to 14.5 volts while the controller throttled down as it should.
The controller (provided it lasts) may be one of those odd gems, with it's smoked see through case, readouts you can read from odd angles and accuracy with zip heat output...panels still kicking after 14 years!
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Steve_S
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# Posted: 21 Aug 2025 12:00pm
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Pleasant Surprise indeed and I'm willing to bet, you had serious doubts about those old "crusty" panels eh. Do you have a link for that MPPT Solar Controller ? I'm curious about it.
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travellerw
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# Posted: 21 Aug 2025 03:01pm
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I had 18 year old Shell solar panels on our boat. They had begun to get the brown spots of death. Yet they still produced more than their rating on some days.
Another cruiser we were friends with "rescued" 1000s of watts of panels out of the garbage that big boats threw away because they were bad. Pretty much every one of them was a wiring issue or dead bypass diode. MC4 connectors suck, especially if you mix different brands of use off brands.
Panels last a lot longer than people think.
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gcrank1
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# Posted: 21 Aug 2025 05:03pm
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Yet I suspect the power companies with the solar fields will mass replace at a point in time, likely keep a replacement rotation going on, just like big business replaces all their light bulbs rather than just replace as they go bad.
Where will they end up? My guess is a panel graveyard rather than the secondary market.
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groingo
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# Posted: 21 Aug 2025 06:46pm - Edited by: groingo
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Steve_S
Keep in mind these are sold under many different names but the real manufacturer is Shengen.
https://www.amazon.com/dp/B0DZ29WBVR?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
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groingo
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# Posted: 21 Aug 2025 06:49pm - Edited by: groingo
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travellerw
Mine looked like they were rusting yet never leaked and all are thick with snail trails, according to various sources online they were toast and I too had issues with the MC4 connectors cracking, leaking and shorting so I manually tied the wires and sealed, no more MC4's.
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gcrank1
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# Posted: 21 Aug 2025 10:51pm
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Think my old panels have MC3's!!!, well, the few that are left. Last time used a few years ago they were working to rating on a fine day. They are sitting inside storage now, dont think they deteriorate stored well do they?
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paulz
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# Posted: 25 Aug 2025 07:09pm
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My shop roof contains all my old panels. That rack of 12 panels, I was buying something else off CL and he said he’d sell that rack for next to nothing, so long ago I forget. Don’t know how it’s wired, comes out in two pairs of leads. Have all this junk charging my shop leds and yard cam, does that ok. Guess I could measure them, probably 20 years old.
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gcrank1
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# Posted: 25 Aug 2025 09:34pm
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That is a Nasty Looking array!
Cant help but wonder what king of output you'd get if you cleaned em off and re-did all the connections.
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paulz
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# Posted: 26 Aug 2025 12:08pm
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I plan to clean and test them today. What’s the test, open voltage, amps?
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gcrank1
Member
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# Posted: 26 Aug 2025 01:55pm
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I suggest not even testing, just clean (cause ya know ya need to) then redo ALL the elec connections you see and can get at, they are probably all in poor shape.
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paulz
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# Posted: 26 Aug 2025 07:42pm
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Went down and blew them off then played around. Whole array comes out in two pairs. Both measured equally 34 volts. Label says 17v so they must be paired up. Nicely put together with copper stranded. Only took one cover off. My VOM didn’t have dc amp fitting so couldn’t check that.
So, be better to run more in series? What about those Schengen SCCs, good?
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groingo
Member
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# Posted: 27 Aug 2025 08:29pm - Edited by: groingo
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Typical older panels, that's some beefy wiring, are they wired in Series or Parallel, (looks like Series on the tag) From your tags looks like a 40 amp SCC would do fine.
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travellerw
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# Posted: 27 Aug 2025 10:43pm
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Parallel is MUCH better for shade. Based on your location they are probably configured pretty decent. I wouldn't change them.
I mean we can get into semantics. 34V is pretty low and a quality MPPT wants more voltage... bla bla bla..
But you have been using them so far and things are good. Sure you might get more with some tweaking, but will the juice be worth the squeeze for your use? Probably not!
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paulz
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# Posted: 28 Aug 2025 12:47pm
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Yes these must be 2 parallel,3 pairs in series, two sets, 12 panels total. This morning, in total shade, as they always are for about 23 hours a day, one measured .3 amps, the other .2xx. If I happen to be down there and catch in the sun I will measure.
But again all it has to do is keep my trail cam going and a couple shop LEDs when I go for a tool. One 12v car battery.
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groingo
Member
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# Posted: 28 Aug 2025 01:36pm - Edited by: groingo
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Just got my 40 amp replacement SCC for the problem child 60 amp SCC (which was putting out half of the 40 amp) and all is well in the world, output is back up where it should be, for $60.00 all in I couldn't ask for more and if it doesn't perform send it back!
https://www.amazon.com/dp/B0DZ2CYXWD?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1&tag=smaca b-20
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