kelabar
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Post by kelabar on Sept 17, 2020 18:49:28 GMT 10
There are hundreds of solar panels from old rooftop installations available at very low prices on gumtree.
They do degrade over time but IIUC the performance only drops off slowly over about 20 years. If so how would you check the panels? Would testing the open circuit voltage in direct sunlight be a good enough indicator (within 10% or so). Or do you need to check the current output as well? Are there easy ways to do this? TIA.
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shinester
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China's white trash
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Post by shinester on Sept 19, 2020 15:21:15 GMT 10
Go with the BLUE panels, never the red ones [produce half the power]. Solar panels are incredibly simple electronics and other than the wire connections will work if not cracked. I personally wouldn't worry about testing them if they're not cracked [look at the cells], though if you like, putting light on them ought to generate a voltage you can test with a multi-meter. Yes old panels are great value, so cheap, no reason to buy new ones when there's usually only 1-4% difference in efficiency and 0-20% loss of generation depending on age and they're 1/4 - 1/2 the cost. No brainer.
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kelabar
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Post by kelabar on Sept 26, 2020 15:29:17 GMT 10
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bug
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Post by bug on Sept 28, 2020 8:24:32 GMT 10
Been looking on Gumtree. You can get a 1.2kW system including the inverter for under $1k. At that price I'd say get a few spare panels in case some of the ones you have are not performing well. Solar panels have been great for us. I have a 5kW grid connected system. It cost $6k all up and we do not have a power bill during summer. Normal bill for us is $250pm. So that's a 6-8 year payback, even ignoring winter. In reality it would be a 5 year payback.
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Morgo
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Post by Morgo on Sept 28, 2020 11:16:27 GMT 10
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Beno
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Post by Beno on Oct 4, 2020 11:46:05 GMT 10
Can you use rooftop panels with solar charge regulator for camping? I looked at an amorphous type producing 120ish watts and they want $2300. At that price they can GGF.
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kelabar
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Post by kelabar on Oct 4, 2020 17:17:39 GMT 10
Can you use rooftop panels with solar charge regulator for camping? I looked at an amorphous type producing 120ish watts and they want $2300. At that price they can GGF. You can. Just match the controller voltage range to the panel voltage. The standard 'camping' panels are usually 12V, the rooftop ones 24V or maybe higher. EDIT: Oops. Need to check the current or Amps rating as well. The other thing to watch out for is the size of the panel. A lot of the rooftop ones are big. This makes them difficult to transport and set up. Mounting them permanently or semi-permanently on a caravan, trailer or roof-rack would help with this. Most of the camping panels are foldable which helps. Also I'm not sure how rugged the rooftop ones would be if moved around a lot or subjected to a lot of road shocks or corrugations. The camping ones are tough!
Check on gumtree for cheap rooftop panels. If you know anyone who works in solar, check with them and see if they have anything laying around.
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bug
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Post by bug on Oct 5, 2020 8:10:22 GMT 10
Can you use rooftop panels with solar charge regulator for camping? I looked at an amorphous type producing 120ish watts and they want $2300. At that price they can GGF. Yes. The regulators are very cheap (you'll need to get one). It may be worth buying a connector and making up a plug for it so that you can re-mount on your roof once finished. Rooftop panels are vastly cheaper than the 4WD type, mostly due to the sheer number in production. It's in the tens-hundreds of millions of panels manufactured every year, so the price point is very low now. Very different to a decade ago.
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malewithatail
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Post by malewithatail on Feb 9, 2021 19:46:24 GMT 10
Yup, simple tests are the best, check in full sun the open circuit voltage, that should be on the panel somewhere. Check the panel can deliver current, switch yr multimeter to 10 amps and check that the current is around what the nameplate states. This test can catch you out though, if the panel has a crook connection, the amps test is nearly a short circuit and can temporarily weld the poor connection together and trick u into thinking the panel is OK. Without some specialized gear its hard to determine the quality of the panel. Its inconvenient to work upside down under the panel in full sun, so I've made up a bench with 4 off 40 watt Fluro lights, and some standoff made from scrap timber. This enables me to place the panel face down on the bench and carry out tests without hanging under it in the hot sun. Mind the eyes though as there is a lot of light from the Fluro's. At a MPP of 37 volts, and assuming a 250 watt panel, then the current is about 6.8 amps, so the resistance needed for max power is about 37/6.8=5.5 ohms. The power rating of the resistor is obviously 250 watts. You can get some resistance wire from Jaycar and wind a resistor to suit, or try and find a commercial one for less than $100.
I'm connected to the universe, but I forgot my password.
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doglover
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Post by doglover on Feb 10, 2021 8:50:33 GMT 10
I haven’t seen any used panels for sale. Can’t say I’d be worried much about them though if not beat up, cracked and put out voltage. The price of panels has come down a lot and is still dropping so that’s the easy part in my mind. The battery bank is where your costs are and they don’t have the incredibly long lifespan of the panels unfortunately. I’m really hope there will be some kind of battery technology in the near future that lowers cost and increases lifespan. One can dream!
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malewithatail
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Post by malewithatail on Feb 10, 2021 15:54:36 GMT 10
Ive picked up useable panels from the tip, and some dead ones that usually turn out to have a dry joint either on an intercell connector (usually visible and easy to repair) or on the terminal box. Occasionally I find a dead bypass diode that's shorted, and once again, that's easy to just remove to get the panel operational again.
All reality is aspect dependent.
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bug
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Post by bug on Feb 10, 2021 19:03:09 GMT 10
I haven’t seen any used panels for sale. Can’t say I’d be worried much about them though if not beat up, cracked and put out voltage. The price of panels has come down a lot and is still dropping so that’s the easy part in my mind. The battery bank is where your costs are and they don’t have the incredibly long lifespan of the panels unfortunately. I’m really hope there will be some kind of battery technology in the near future that lowers cost and increases lifespan. One can dream! Ebay has shedloads of them. About $100 each and in working order.
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