How best to find the "best" small solar panel of a particular size?
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@NeverDie I bought my first two over a year ago. Have not used them yet. So no, nothing useful unfortunately.
@mfalkvidd
It's a pity this topic hasn't attracted more interest. I guess people are happy with their batteries. -
There seems to be a sweet spot at 6V 1W when it comes to price/performance, at least specified performance. Smaller panels are relatively expensive, and so are larger. I have ordered four of these but they haven't arrived yet.
I have been looking for flexible panels, something that could be folded or rolled up, but haven't found anything with a decent price so far.
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I think that's because that's where the market demand is. It's hard to find smaller panels generally. I have these on order, but neither has yet arrived:
https://www.aliexpress.com/snapshot/0.html?orderId=83597824322273&productId=32253274314
https://www.aliexpress.com/snapshot/0.html?orderId=83519564882273&productId=32644217312
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The problem of adding up panels is that your node would get quite big. The other day I was listening to a podcast and they were talking about a new sensor device with a special paint on the case that acts as a solar panel that charges the internal battery/supercap that needs to be much smaller than usual battery powered sensors
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The problem of adding up panels is that your node would get quite big. The other day I was listening to a podcast and they were talking about a new sensor device with a special paint on the case that acts as a solar panel that charges the internal battery/supercap that needs to be much smaller than usual battery powered sensors
@gohan said in How best to find the "best" small solar panel of a particular size?:
The problem of adding up panels is that your node would get quite big. The other day I was listening to a podcast and they were talking about a new sensor device with a special paint on the case that acts as a solar panel that charges the internal battery/supercap that needs to be much smaller than usual battery powered sensors
Yes, that's why I mentioned that Solar Bits (which are just 7mm x 22mm in size but deliver 4.7v) might be a good fit for multiple panels in series. The sum of their areas wouldn't be large. But they come at a price... https://www.digikey.com/product-detail/en/ixys/KXOB22-01X8F/KXOB22-01X8F-ND/4840081
Do you have a link to the podcast? Never before heard of a paint that produces solar power. Is it something I can buy?
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@mfalkvidd said in How best to find the "best" small solar panel of a particular size?:
@NeverDie Interesting. Let us know what result you get.
I just now tried four 6v panels powered in series by moonlight just to see what would happen, and it produced only 0.06v. :( So, scratch that idea.
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@mfalkvidd said in How best to find the "best" small solar panel of a particular size?:
@NeverDie Interesting. Let us know what result you get.
I just now tried four 6v panels powered in series by moonlight just to see what would happen, and it produced only 0.06v. :( So, scratch that idea.
@NeverDie ths is slightly off topic, but can you recommend any rectifier with low drop voltage to use to prevent the solar panel from discharging the supercap/battery? I'm not comfortable with SMD, so I need to find something that's big enough to hand solder, has low drop and doesn't cost too much.
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@gohan said in How best to find the "best" small solar panel of a particular size?:
The problem of adding up panels is that your node would get quite big. The other day I was listening to a podcast and they were talking about a new sensor device with a special paint on the case that acts as a solar panel that charges the internal battery/supercap that needs to be much smaller than usual battery powered sensors
Yes, that's why I mentioned that Solar Bits (which are just 7mm x 22mm in size but deliver 4.7v) might be a good fit for multiple panels in series. The sum of their areas wouldn't be large. But they come at a price... https://www.digikey.com/product-detail/en/ixys/KXOB22-01X8F/KXOB22-01X8F-ND/4840081
Do you have a link to the podcast? Never before heard of a paint that produces solar power. Is it something I can buy?
@NeverDie I have to look at it but it's in Italian and the paint it wasn't just simple paint, but different layers of semiconductor materials printed on the case, so something quite difficult to do at home.
@mfalkvidd I usually seen schottky diodes on the solar panel for that purpose.
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@NeverDie ths is slightly off topic, but can you recommend any rectifier with low drop voltage to use to prevent the solar panel from discharging the supercap/battery? I'm not comfortable with SMD, so I need to find something that's big enough to hand solder, has low drop and doesn't cost too much.
Not sure about through-hole blocking diodes. I'm using 1PS79SB30, which is SMD, but reverse current leakage is just 10na. Practically all the new good stuff is SMD, so you're severely impaired if you don't make the jump to SMD. SMD is nothing to be afraid of. Presently I'm hand soldering everything, including all SMD parts.
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Not sure about through-hole blocking diodes. I'm using 1PS79SB30, which is SMD, but reverse current leakage is just 10na. Practically all the new good stuff is SMD, so you're severely impaired if you don't make the jump to SMD. SMD is nothing to be afraid of. Presently I'm hand soldering everything, including all SMD parts.
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@NeverDie thanks. How do you handle lead times för pcb manifacturing? Or is it possible to buy prototype pcb cards? I'm worried project lead times will 10x if I need to wait for pcb milling for each iteration.
@mfalkvidd said in How best to find the "best" small solar panel of a particular size?:
@NeverDie thanks. How do you handle lead times för pcb manifacturing? Or is it possible to buy prototype pcb cards? I'm worried project lead times will 10x if I need to wait for pcb milling for each iteration.
I'm not sure how others handle it, but what I do is solder each individual SMD part onto pre-made breakout board for SMD parts. Here's an example of one I use frequently: https://www.aliexpress.com/item/100pcs-SOT23-SOP10-MSOP10-Umax-SOP23-to-DIP10-Pinboard-SMD-To-DIP-Adapter-Plate-0-5mm/32769473900.html?spm=2114.13010608.0.0.exgj0t
Then I attach header pins to it and complementary header pins onto a general purpose protoboard, such as: https://www.aliexpress.com/item/10pcs-3X7cm-3-7cm-Double-Side-Prototype-pcb-Breadboard-Universal-for-Arduino-1-6mm2-54mm-Practice/32655345057.html?spm=2114.13010608.0.0.exgj0t
Then I literally plug the SMD part into the protoboard. I then solder wired connections among the various parts. Sometimes I'll use breadboards, but I prefer this method because the wiring on breadboards can get rather loose, which becomes a headache, whereas doing soldered wire connections on protoboard, the connections are great quality and "made" forever until you decide to change them. I do it this way first rather than going straight to PCB because of the long PCB fab time (on average around 2 weeks for me from OSH PARK). Once I verify the design is correct using the protoboard, then I'll translate it to PCB as the final step. Also, while I'm waiting for the PCB to arrive, I have a solid working prototype, so I can continue working on whatever is next and the turnaround time for PCB fabrication isn't quite so painful.Does that answer your question?
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@mfalkvidd said in How best to find the "best" small solar panel of a particular size?:
@NeverDie thanks. How do you handle lead times för pcb manifacturing? Or is it possible to buy prototype pcb cards? I'm worried project lead times will 10x if I need to wait for pcb milling for each iteration.
I'm not sure how others handle it, but what I do is solder each individual SMD part onto pre-made breakout board for SMD parts. Here's an example of one I use frequently: https://www.aliexpress.com/item/100pcs-SOT23-SOP10-MSOP10-Umax-SOP23-to-DIP10-Pinboard-SMD-To-DIP-Adapter-Plate-0-5mm/32769473900.html?spm=2114.13010608.0.0.exgj0t
Then I attach header pins to it and complementary header pins onto a general purpose protoboard, such as: https://www.aliexpress.com/item/10pcs-3X7cm-3-7cm-Double-Side-Prototype-pcb-Breadboard-Universal-for-Arduino-1-6mm2-54mm-Practice/32655345057.html?spm=2114.13010608.0.0.exgj0t
Then I literally plug the SMD part into the protoboard. I then solder wired connections among the various parts. Sometimes I'll use breadboards, but I prefer this method because the wiring on breadboards can get rather loose, which becomes a headache, whereas doing soldered wire connections on protoboard, the connections are great quality and "made" forever until you decide to change them. I do it this way first rather than going straight to PCB because of the long PCB fab time (on average around 2 weeks for me from OSH PARK). Once I verify the design is correct using the protoboard, then I'll translate it to PCB as the final step. Also, while I'm waiting for the PCB to arrive, I have a solid working prototype, so I can continue working on whatever is next and the turnaround time for PCB fabrication isn't quite so painful.Does that answer your question?
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Back to the OP. I finally received these smaller solar panels:
https://www.aliexpress.com/item/10Pcs-Lot-5V-30mA-53X30mm-Micro-Mini-Small-Power-Solar-Cells-Panel-For-DIY-Toy-3/32811111041.html?spm=2114.01010208.3.10.2aPJ36&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10130_10068_5160013_436_10136_10157_10137_10060_10138_10155_10062_10156_10154_10056_10055_10054_10059_100032_100033_100031_10099_10103_10102_10096_10147_10052_10053_10050_10107_10142_10051_5150015_10084_10083_10119_10080_10082_10081_10178_10110_10111_10112_10113_10114_10037_10181_10183_10182_10185_10033_10032_10078_10079_10077_10073_10123_10120-10033_10077,searchweb201603_4,ppcSwitch_4&btsid=98b799be-2ff3-401c-aaeb-fa49f82cdc7c&algo_expid=a78e15b1-b89c-40bf-849b-b9f99d840f0d-1&algo_pvid=a78e15b1-b89c-40bf-849b-b9f99d840f0d
However, they're disappointing. They do produce 5v if put into direct sunlight. However, indoors, they produce maybe 1/3 the open-circuit volts of a larger mini panel. Instead, I had expected it would produce the same open circuit voltage, but simply able to produce less current.So, I think what may be going on is that these panels may have some kind of internal leakage. In direct sunlight, that leakage is relatively small. However, in the less good mini solar panels, that internal leakage starts to dominate as lighting conditions get dimmer.
I've tested even smaller mini solar panels from Digikey, and they do manage to produce much more voltage under dimmer lighting than these cheap ones from China, which I'm now doubting will be of much use to me.
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Back to the OP. I finally received these smaller solar panels:
https://www.aliexpress.com/item/10Pcs-Lot-5V-30mA-53X30mm-Micro-Mini-Small-Power-Solar-Cells-Panel-For-DIY-Toy-3/32811111041.html?spm=2114.01010208.3.10.2aPJ36&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10130_10068_5160013_436_10136_10157_10137_10060_10138_10155_10062_10156_10154_10056_10055_10054_10059_100032_100033_100031_10099_10103_10102_10096_10147_10052_10053_10050_10107_10142_10051_5150015_10084_10083_10119_10080_10082_10081_10178_10110_10111_10112_10113_10114_10037_10181_10183_10182_10185_10033_10032_10078_10079_10077_10073_10123_10120-10033_10077,searchweb201603_4,ppcSwitch_4&btsid=98b799be-2ff3-401c-aaeb-fa49f82cdc7c&algo_expid=a78e15b1-b89c-40bf-849b-b9f99d840f0d-1&algo_pvid=a78e15b1-b89c-40bf-849b-b9f99d840f0d
However, they're disappointing. They do produce 5v if put into direct sunlight. However, indoors, they produce maybe 1/3 the open-circuit volts of a larger mini panel. Instead, I had expected it would produce the same open circuit voltage, but simply able to produce less current.So, I think what may be going on is that these panels may have some kind of internal leakage. In direct sunlight, that leakage is relatively small. However, in the less good mini solar panels, that internal leakage starts to dominate as lighting conditions get dimmer.
I've tested even smaller mini solar panels from Digikey, and they do manage to produce much more voltage under dimmer lighting than these cheap ones from China, which I'm now doubting will be of much use to me.
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I suppose if you were to boost them, then for some inside applications, like a potted plant moisture meter, they would be adequate because for that you don't actually need updates all that often. So, they may not be a complete loss, but they aren't as good as even smaller panels that you can buy on digikey for more money. For instance, in my testing, this micro panel performs much better indoors than the cheap Chinese ones, and it's smaller too: https://www.digikey.com/product-detail/en/panasonic-bsg/AM-5610CAR/869-1009-ND/2165194
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I just completed a battery-free outdoor node reporting temp/humid based on the information in this thread. Works great, thanks to @NeverDie for his insights. Node is a sensebender micro, RFM69W, 10F supercapacitor, and 5V solar panel. Reporting every 4 minutes it sends temp, humid, supercap %, & solar V. Uses the simple tiny solar charger schematic from @NeverDie shown above.
Results: The supercapacitor cost $2 at Digikey, is about 2/3 the size of a AAA battery, and lasts 40 hours without the solar panel connected. The 40 hours is when the supercapacitor reaches 1.9v as the low end for operating the node. Easily gets through the longer dark winter nights.
The solar panel is from China, Ebay, 110mmx70mm, 5V, 1.25W. The panel works great also. It reaches 4V in the smallest amount of light, and 5.45V (no load) in modest indirect light. In fact, it will fully recharge the supercapacitor in the morning before the sun even rises above the horizon, just from the sky brightening. (From the ~20% overnight discharged state.) It seems to charge a fully empty supercap in ~10 minutes under average light.
Bottom line: no longer walking through 1ft of snow in 10 degrees (F) to get the node, bring it inside, remove water seals, and change the batteries. This is the solution I was looking for.
Also have a 2nd outside node in testing using the Ceech solar board (A great PCB also!), a 18650 battery and the same solar panel. So far the battery has gone 2 months and is at 3.85V without the panel connected. In testing, the solar panel has no problem charging the battery. In fact so much, I am going to add a FET to disconnect the solar panel periodically to allow the battery to cycle some.
This site is excellent, such great talent, thank you all!
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I just completed a battery-free outdoor node reporting temp/humid based on the information in this thread. Works great, thanks to @NeverDie for his insights. Node is a sensebender micro, RFM69W, 10F supercapacitor, and 5V solar panel. Reporting every 4 minutes it sends temp, humid, supercap %, & solar V. Uses the simple tiny solar charger schematic from @NeverDie shown above.
Results: The supercapacitor cost $2 at Digikey, is about 2/3 the size of a AAA battery, and lasts 40 hours without the solar panel connected. The 40 hours is when the supercapacitor reaches 1.9v as the low end for operating the node. Easily gets through the longer dark winter nights.
The solar panel is from China, Ebay, 110mmx70mm, 5V, 1.25W. The panel works great also. It reaches 4V in the smallest amount of light, and 5.45V (no load) in modest indirect light. In fact, it will fully recharge the supercapacitor in the morning before the sun even rises above the horizon, just from the sky brightening. (From the ~20% overnight discharged state.) It seems to charge a fully empty supercap in ~10 minutes under average light.
Bottom line: no longer walking through 1ft of snow in 10 degrees (F) to get the node, bring it inside, remove water seals, and change the batteries. This is the solution I was looking for.
Also have a 2nd outside node in testing using the Ceech solar board (A great PCB also!), a 18650 battery and the same solar panel. So far the battery has gone 2 months and is at 3.85V without the panel connected. In testing, the solar panel has no problem charging the battery. In fact so much, I am going to add a FET to disconnect the solar panel periodically to allow the battery to cycle some.
This site is excellent, such great talent, thank you all!
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I just completed a battery-free outdoor node reporting temp/humid based on the information in this thread. Works great, thanks to @NeverDie for his insights. Node is a sensebender micro, RFM69W, 10F supercapacitor, and 5V solar panel. Reporting every 4 minutes it sends temp, humid, supercap %, & solar V. Uses the simple tiny solar charger schematic from @NeverDie shown above.
Results: The supercapacitor cost $2 at Digikey, is about 2/3 the size of a AAA battery, and lasts 40 hours without the solar panel connected. The 40 hours is when the supercapacitor reaches 1.9v as the low end for operating the node. Easily gets through the longer dark winter nights.
The solar panel is from China, Ebay, 110mmx70mm, 5V, 1.25W. The panel works great also. It reaches 4V in the smallest amount of light, and 5.45V (no load) in modest indirect light. In fact, it will fully recharge the supercapacitor in the morning before the sun even rises above the horizon, just from the sky brightening. (From the ~20% overnight discharged state.) It seems to charge a fully empty supercap in ~10 minutes under average light.
Bottom line: no longer walking through 1ft of snow in 10 degrees (F) to get the node, bring it inside, remove water seals, and change the batteries. This is the solution I was looking for.
Also have a 2nd outside node in testing using the Ceech solar board (A great PCB also!), a 18650 battery and the same solar panel. So far the battery has gone 2 months and is at 3.85V without the panel connected. In testing, the solar panel has no problem charging the battery. In fact so much, I am going to add a FET to disconnect the solar panel periodically to allow the battery to cycle some.
This site is excellent, such great talent, thank you all!
-
I just completed a battery-free outdoor node reporting temp/humid based on the information in this thread. Works great, thanks to @NeverDie for his insights. Node is a sensebender micro, RFM69W, 10F supercapacitor, and 5V solar panel. Reporting every 4 minutes it sends temp, humid, supercap %, & solar V. Uses the simple tiny solar charger schematic from @NeverDie shown above.
Results: The supercapacitor cost $2 at Digikey, is about 2/3 the size of a AAA battery, and lasts 40 hours without the solar panel connected. The 40 hours is when the supercapacitor reaches 1.9v as the low end for operating the node. Easily gets through the longer dark winter nights.
The solar panel is from China, Ebay, 110mmx70mm, 5V, 1.25W. The panel works great also. It reaches 4V in the smallest amount of light, and 5.45V (no load) in modest indirect light. In fact, it will fully recharge the supercapacitor in the morning before the sun even rises above the horizon, just from the sky brightening. (From the ~20% overnight discharged state.) It seems to charge a fully empty supercap in ~10 minutes under average light.
Bottom line: no longer walking through 1ft of snow in 10 degrees (F) to get the node, bring it inside, remove water seals, and change the batteries. This is the solution I was looking for.
Also have a 2nd outside node in testing using the Ceech solar board (A great PCB also!), a 18650 battery and the same solar panel. So far the battery has gone 2 months and is at 3.85V without the panel connected. In testing, the solar panel has no problem charging the battery. In fact so much, I am going to add a FET to disconnect the solar panel periodically to allow the battery to cycle some.
This site is excellent, such great talent, thank you all!
