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Find out if it's possible to power Christmas lights with solar energy during the Scottish winter, despite the short days and low sun. Discover how small solar panels can be used to charge a lithium cell and potentially provide a sustainable and eco-friendly option for your holiday decorations.

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[0:00] in a previous video we made some of our
[0:02] Christmas lights rechargeable and one of
[0:04] the viewers suggested why not make them
[0:06] solar powered as well now I made the
[0:08] obvious joke of creating an infinite
[0:10] energy machine with the lights power in
[0:12] the solar cell which then power the
[0:14] light which then power the solar cell
[0:16] you get the idea eventually it would
[0:18] explode but it got me thinking is it
[0:21] even possible in the Scottish winter to
[0:23] run the lights off solar power now
[0:25] contrary to popular belief it is
[0:27] actually quite sunny in Scotland the
[0:30] only problem is being quite far north
[0:32] our winter days are pretty short you can
[0:35] see this from the calculator here
[0:36] Edinburgh is around 56 degrees north so
[0:40] around this time of year the sun rises
[0:41] about 9 A.M and sets about 3 P.M but you
[0:45] can see that during the summer it’s
[0:46] rising at about 3 30 am and setting it
[0:49] about 8 PM we do get really long days in
[0:52] the summer but in Winter pretty short
[0:55] using this next calculator we can work
[0:57] out what the best tilt for our panel is
[0:59] the sun is so low that we need to be
[1:01] almost pointing at the Horizon for
[1:04] maximum power reading off the graph we
[1:06] should get around two kilowatt hours per
[1:08] meter Square so I thought it was worth a
[1:11] go and ordered some small solar panels
[1:13] off Amazon using the two kilowatt hour
[1:16] per meter Square value with the size of
[1:18] our little cells we’ll have around 4.55
[1:21] Watt hours of sunshine our panels should
[1:24] be around 20 efficient so we’ll get 0.91
[1:28] Watt hours
[1:29] in theory assuming we get 5 volts from
[1:32] our solar panel the maximum we’ll be
[1:34] able to get is around 200 milliamp hours
[1:36] now I have to say this feels very
[1:39] optimistic and pretty unlikely but let’s
[1:42] run some experiments and see I have
[1:44] hacked up the code for my DIY battery
[1:46] discharge tester so it just monitors
[1:48] voltage it’s based around the esp32
[1:51] which is quite handy as it’s a wireless
[1:53] device so I can stick it outside on the
[1:55] balcony and pull readings off it
[1:57] remotely I really don’t want to be
[1:58] standing outside because it is pretty
[2:01] cold this should give us fairly optimal
[2:03] conditions as the balcony faces South
[2:05] and there’s not much in the way rather
[2:08] than measuring the open circuit voltage
[2:10] of the solar panel I thought it might be
[2:12] more realistic to measure it under load
[2:14] so I’m feeding it into a voltage divider
[2:16] made up of two 220 ohm resistors this
[2:20] will give us about 10 milliamps when the
[2:21] solar panel is outputting 5 volts we do
[2:24] need the voltage divider as the esp32 is
[2:27] a 3.3 volt device so we need to get our
[2:29] voltage into that range
[2:32] I’ve left the panel on our South racing
[2:34] balcony and recorded the output of the
[2:35] solar panel at this point I’d just like
[2:38] to say thanks to PCB way for powering
[2:40] the YouTube channel over the past couple
[2:42] of years there probably wouldn’t be a
[2:44] channel without them and there certainly
[2:45] wouldn’t be any pcbs for projects check
[2:48] out a link to them in the description
[2:49] they do a really good job
[2:52] the results look kind of promising even
[2:55] with our weak sunshine and shadows from
[2:57] the trees and the occasional Cloud there
[2:59] are previous where we might actually get
[3:01] enough voltage and current to charge a
[3:02] lithium cell we might at least be able
[3:05] to harvest enough power to run some LED
[3:07] light strings for a couple of hours at
[3:08] low brightness
[3:10] calculating the current based off this
[3:12] voltage and our fixed resistors and
[3:14] integrating the area under the curve I
[3:16] think we managed to get about 33
[3:18] milliamp hours it’s not much but it’s
[3:21] better than nothing
[3:22] I’ve got one of these tp4056 charging
[3:25] boards and I’ve removed the charge
[3:26] indicator LEDs so that we don’t waste
[3:29] any power hopefully this board won’t
[3:31] have the same issue that one of my other
[3:32] boards had where it was draining the
[3:34] battery when it wasn’t charging check
[3:36] out the video that should be in the top
[3:37] corner right now if you’re interested in
[3:39] that investigation it was pretty fun
[3:42] I’ve also taken one of my Savage lithium
[3:44] cells and discharged it completely we’ll
[3:47] hook this up to the charger board and
[3:48] leave it in the window for a day
[3:50] unfortunately after making all these
[3:52] great claims about Scotland Being Sunny
[3:54] the weather forecast for the next few
[3:56] days was pretty dire even measuring the
[3:59] open circuit of one of the cells gives
[4:01] us a pretty bad result this won’t charge
[4:03] anything but with two cells in series we
[4:06] get a reasonable voltage and adding
[4:08] another two in parallel means that we
[4:10] might actually be able to get some power
[4:12] after a day on the windowsill we’ve got
[4:14] some results there was no sun at all but
[4:17] we have managed to raise the voltage of
[4:18] the cell by a very tiny amount but it is
[4:21] a very tiny amount so I’ve discharged
[4:24] the battery again this time I’ve tried
[4:26] to get it to exactly three volts and
[4:28] we’ve got a pretty reasonable day
[4:29] forecast I’m trying it with just a
[4:32] single cell and we’re getting quite a
[4:33] good voltage even with it under load
[4:35] connected to the charger it’s quite a
[4:37] nice day so hopefully we’ll get some
[4:39] good results and some sunshine
[4:41] well the sun is pretty much down and
[4:44] looking at the voltage coming from the
[4:45] cells we might as well call this
[4:46] experiment done we managed to raise the
[4:49] voltage by a whopping 0.2 volts over the
[4:52] day which is definitely better than the
[4:54] last time but according to my battery
[4:56] discharge test we only managed to get a
[4:58] measly 10 milliamp hours into the
[5:00] battery not a great result at all but
[5:03] probably about right given that the
[5:04] solar cell is on the windowsill indoors
[5:07] and the weather has been a bit worse
[5:09] than normal not a great deal of sun
[5:11] really so I think maybe we could double
[5:13] this on a good day and get 20 milliamp
[5:15] hours so I’m going to call this
[5:17] borderline possible we could definitely
[5:19] run our LED string at a lower current
[5:21] and on a good day get a couple of hours
[5:23] of run time all in all a pretty
[5:25] interesting experiment but I think for
[5:27] now I’ll stick to charging my lights via
[5:29] USB thanks for watching I’m going to
[5:32] take a break now for Christmas and I’ll
[5:33] see you all in the new year

HELP SUPPORT MY WORK: If you're feeling flush then please stop by Patreon Or you can make a one off donation via ko-fi
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Chris Greening

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A collection of slightly mad projects, instructive/educational videos, and generally interesting stuff. Building projects around the Arduino and ESP32 platforms - we'll be exploring AI, Computer Vision, Audio, 3D Printing - it may get a bit eclectic...

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