How best to find the "best" small solar panel of a particular size?
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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!
-
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!
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@novas said in How best to find the "best" small solar panel of a particular size?:
@novicit Could you share schematic and software of your node?
also links to the hardware would be appreciated ;)
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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!
@novicit said in How best to find the "best" small solar panel of a particular size?:
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.
I'm not aware of any advantages to cycling a LiPo battery. As mentioned by Gohan, though, charging to just 80% does seem to extend lifespan.
Better yet, use a LiFeP04 battery. They're safer, and you don't need to down convert their voltage because their max charge is 3.6v.
I prefer supercaps mainly because they should last practically forever.
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@novicit said in How best to find the "best" small solar panel of a particular size?:
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.
I'm not aware of any advantages to cycling a LiPo battery. As mentioned by Gohan, though, charging to just 80% does seem to extend lifespan.
Better yet, use a LiFeP04 battery. They're safer, and you don't need to down convert their voltage because their max charge is 3.6v.
I prefer supercaps mainly because they should last practically forever.
@NeverDie Did you look at @ceech solar harvesting boards?
My experience with solar panels is this. There are so many of them with the claiming same spec,. but behaving differently in real life. I think the same reason is quality. I have a weather station using ceech's board with temp/hum/baro/lightning/light sensors and nrf24l01+, 5V 1.2W solar panel and 3.7v 400mA LiPO. This has been running for some time. I was actually surprised that the battery is being charged even on a dark winter day. Some harvesting even is possible without the sun.Now I have been looking at replacing LiPO with a solar harvesting board and a few supercaps. Do you think 10F would be enough? Or shall I go for something higher like 20F or 50F?
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Interestingly, in direct sunlight they all measure at an open circuit voltage of 7v +- 0.1v. So, go figure as to why the range is so much wider under dim conditions.
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@NeverDie were they all at the same angle to the light source? If you laid them out on a table and shone a lamp, theynwill be at different angles and have different results.
@wallyllama I would say that in the similar circumstances different solar panels do behave differently due to quality solar cells, i.e. manufacturing quality as well as efficiency.
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@novicit said in How best to find the "best" small solar panel of a particular size?:
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.
I'm not aware of any advantages to cycling a LiPo battery. As mentioned by Gohan, though, charging to just 80% does seem to extend lifespan.
Better yet, use a LiFeP04 battery. They're safer, and you don't need to down convert their voltage because their max charge is 3.6v.
I prefer supercaps mainly because they should last practically forever.
@NeverDie said in How best to find the "best" small solar panel of a particular size?:
@novicit said in How best to find the "best" small solar panel of a particular size?:
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.
Thanks for the pointer to Ceech. I hadn't been aware of him, but I see that his Ebay store has a lot of interesting boards, including this one:
http://www.ebay.com/itm/Solar-Energy-Harvesting-power-supply-w-LTC3108-and-super-capacitor-storage-/331974364829?hash=item4d4b36ce9d:g:tXwAAOSwmLlX4Osy
which I may order just for fun.Impossible for me to really answer your question, as it all depends on what your current drains are. A 10F supercap isn't really much compared to a 400mah Lipo.
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@NeverDie said in How best to find the "best" small solar panel of a particular size?:
@novicit said in How best to find the "best" small solar panel of a particular size?:
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.
Thanks for the pointer to Ceech. I hadn't been aware of him, but I see that his Ebay store has a lot of interesting boards, including this one:
http://www.ebay.com/itm/Solar-Energy-Harvesting-power-supply-w-LTC3108-and-super-capacitor-storage-/331974364829?hash=item4d4b36ce9d:g:tXwAAOSwmLlX4Osy
which I may order just for fun.Impossible for me to really answer your question, as it all depends on what your current drains are. A 10F supercap isn't really much compared to a 400mah Lipo.
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That's a simple circuit, but it lacks the balancing of the supercaps or at least the individual overvoltage protection
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It's a buck converter. Here's the datasheet for the chip that's on it: http://cds.linear.com/docs/en/datasheet/35881fc.pdf
So, it's for the case of having a solar panel that produces more volts than the target device can handle. It's a larger solar panel than the ones we've been discussing.
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Even with a 5V panel you still need 2 supercaps in series or get the 5v supercaps but they have less capacitance. I have ordered those 5v 4F too so I'll have to see how they behave
