Hi there! I do lots of camping and outdoor activities and I was asking… does anyone ever use this kind of solar charger?
I never owned one … I think it would be very comfortable in lots of outdoor situations 
Do these solar panels work with cloudy sky or charge the phone/tablet intermittently?
Let me know what do you think about! 
Portable Solar Panel
Hi @JohnWatson,
I use Anker’s Powerport Solar 21w to power my Soundcore Boost, Android phone, iPad, earbuds, headlamp, and various other accessories. Here’s what I have learned:
iPhone / iPad will shift to the lowest common charging speed when plugged into anything. In other words, even if you plug the phone into the panel in direct sun, it will slow down to the slowest speed when a cloud passes over, and that will be the speed it charges at for the rest of that plug-in time.
Instead of charging devices directly, It’s much more intelligent to get a battery (I use a PowerCore II 20000, Astro E1, and a few other batteries in a rotation) to collect solar power then use the batteries to charge your items. It also allows you to carry around a little extra power in case the day isn’t ideal for solar collection.
In any case, I’ve used only this setup to power my full compliment of USB chargeable devices since March, when I got the powerport Solar. In fact, I got a new phone in July and it has never been charged on anything but solar power. Same thing with the SoundCore Boost.
But for this sort of thing to work, you definitely need at least one battery.
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A little technical background to then explain the answers so your question:
The semiconductor in the solar panels releases electrons in the presence of sunlight. The energy of those electrons (Voltage) is a function of the frequency of the light, Ultraviolot (UV) is the strongest light and is stronger at altitude, and when sun is higher in the sky (light passes through less atmosphere which absorbs UV), and when reflection from surfaces like sand, snow.
The quantity of electrons (Current) is a function of the brightness of the light, so the thickness of cloud basically.
So in an extreme example, at night, the light reflected off the moon is enough to make energy, the voltage will be there, but the current won’t.
Then you get a variable voltage based on spectrum, and variable current based on brightness.
Then you got the need to adhere to USB specifications which is realistically a minimum of 4.2V to about 5V. The DC-DC converter in the solar panel compensates for lower spectrum (less UV) via stepping up the Voltage, but that steps down the current. So what you get is a fairly fixed 4.2-5V output and varying current.
If you have understood this so far, then you can predict that if you have a physically bigger panel, then the step-down of current is less, so the current is higher.
Then minimum required input current of your device then will be above the current output of the solar panel more often the bigger you make the panel, so more useful current. This is non-linear, in that double the panel size is going to be more often useful.
Get the biggest panel you can afford, or wish to pack, so in the Anker system the 21W.
A Powercore recharge is more tolerant of varying voltage and current than most devices, a Powercore will recharge its cells on a lower current than devices, so you waste less of the energy. However, putting the energy into the Powercore then taking it out to put into device wasters energy. So if you are in strong sunshine, it is more efficient to plug your device in directly until its at least 70% charged. Once you get to 70%-85% charged then your device will move into trickle charge so you;re wasting energy. Then once your devices are nearly fully charged, then recharge Powercore instead.
A good technique is to plug in both your device and the Powercore together and any unused energy the phone cannot take, goes into Powercore.
It is good to buy a USB meter to measure the current, because in really good conditions you get too much power and it is wasted, in that case the Powercore 26800 and the Powercore II Elite has dual input so it can take all the output in perfect sunny conditions.
TO answer your question, if you get the 21W, you’d expect to see 1A 5W output in suboptimal conditions, useful energy in hazy cloud, and this goes upto about 2.1W 11W in ideal conditions, most phones cannot ingest as fast as 11W, so if you bought the meter, you can find the maximum ingest current of your phone, tablet, etc based on the brightness of the sun, and then learn that and plug in devices and Powercore to make best use of the energy.
In less than ideal conditions, the minimum current of a higher end tablet will stop charging, so consider an intermediate Powercore to capture useful energy and present at higher current to the device.
In a camping situation I tend to take a lower-end phone which accepts lower current, and a smaller tablet which accepts a lower current, as these then tolerate less than ideal conditions and collectively is smaller to carry.
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Hi @ryandhazen, thanks for the answer
I’m evaluating these panels because with my 10,000mah anker power core battery I can not keep in charge all my things for a 10 or more day excursion.
So you advice to connect a power bank to the panel so that it can be recharged and used later on for other devices … I thought a similar thing, not for slow charging of iphone / ipad but not to leave direct sunlight an 800 euro device.
This is another reason for charge my power core with the solar panel.
Thanks for the advice!
Get the largest panel you can afford, or want to pack, so in the Anker system the 21W.
Okay, bigger is better! 
A good technique is to plug in both your device and the Powercore together and any unused energy that the phone can not take, goes into Powercore.
Couldn’t be the reverse? So you charge the power bank and the device, power bank takes the current that it needs and the excess goes to the device?
When sun is weaker, plug in device, if it is recharging then you’re good.
When sun is strong, plug in device and powercore.
Learn about your device tolerance to varying sun using a meter, do that before you rely on solar. Every device is different.
In general use lower power requiring devices when reliant on solar, because they can make useful gain in weaker sun, and lighter to carry and last longer per hour of sun. If you assumed 5Wh/day of sun then size your devices in that budget…
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Thanks for the technical answer!
In general use lower power requiring devices when reliant on solar, because they can make useful gain in weaker sun, and lighter to carry and last longer per hour of sun.
If these Anker solar panels are rainproof do you think it’s a good idea to leave it out and connected to a powercore during the night so at the early lights of the sunrise they are ready to go?
That 10,000 mAh battery will be a perfect fit with a powerport solar. I’d even recommend getting another one because the 21w powerport has 2 outputs, so you can charge two batteries at once.
Not to mention that you don’t really get to use a device while it’s plugged into a panel.
Remember to shade the battery that’s charging from the solar panel. I usually prop up the panel a little bit and slide the battery into it’s shadow to keep the battery cool. You don’t want that battery in direct sunlight either. I’ve had success shading the battery under the panel in 95-100 F (35-38 C) temperatures with direct sunlight above 5000 ft (1524 M).
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I think too that my 10,000mAh will be nice to start. When you recharge two devices simultaneously, the amperage of the individual outputs decreases compared to a single device charging?
Good news that the batteries can keep cool (or nearly) in the little shadow of the solar panel, usually this black solar charger become really hot.
correct, which is why:
- buy a meter
- learn the relationship between sunshine and output
- learn how your device tolerates erratic and lower current.
So I’ll give you two examples:
- my Moto G4 Play is my “camping” or “off-grid” phone because it lasts a long time, it is a less powerful phone, I put a meter on it when attached to a 2A output wall charger and saw it is incapable of ingesting more than 1A
- my smaller tablet for “off-grid” is an old Nexus 7, it cannot ingest more than 1.6A. These two devices cost total of $187, given if I’m hiking an accident can only crack a low cost device.
- in summer noon sun my 21W gives about 2.6A output, so both the phone and the tablet can be recharged concurrently at their fastest possible speed.
- in less than ideal situations I see about 1A output, so then I choose, I plug in the most discharged device.
- if my devices are fully (or mostly, >70%) charge, then in weaker sun I would probably be best recharging the most discharged device, or the most important device (phone first, then tablet).
- in strong sunshine, if I my devices are mostly fully charge, then I’d plug in a 10000mAh Powercore to make use of the energy to story to carry me through any future wet / less-sunny period.
- I find an average of 5Wh to 10Wh/day is realistic from solar, then look at your devices and calculate. The Moto G4 Play in an off-grid situation its 10Wh battery and lasts me 2 days (phone needs 5Wh/day) so you’re talking even in a sustained bad weather period, a few days worth is valid, and then weather turns better and “too much energy” to which the 10000mAh soaks that up then handle the next rainy days, repeat, so pretty much can be off-grid indefinitely.
Each device is different.
Water and solar - I’d not advocate it in general, Anker products are well made and probably tolerate rain but not by design, try to avoid it. One way is to place indoors, inside your tent, and even though the tent shades from sun, you might get something useful. Remember though batteries hate heat. Much better though is to take advantage of dry sunny periods and soak up the energy, either recharge device, or if they are mostly charged store that energy in a 10000mAh Powercore to see you through a damp dull period.
Buy a USB testing meter, they are far more reliable information of what a device tells you, because most devices, when you turn on the screen, to operate an app, they reduce their input due to thermal throttling, so the figure you see is lower than true. You don’t necessarily need to take the meter with you (but they are light and small so why not) but if you spend a few days learning your solar / device interaction at home, it really helps when off-grid, to make best use of your solar budget.
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I bring with me my iPhone 6 for photos, tracking, speed, altitude, weather, and so on.
My iPhone 6 will take max 1.2/1.3 A if I charge it with an iPad charger (max 2.4 A), so I think this is the max speed.
How can I do that? I think a current less than 1 amp could damage the smartphone.[quote=“nigelhealy, post:10, topic:54340”]
- in summer noon sun my 21W gives about 2.6A output, so both the phone and the tablet can be recharged concurrently at their fastest possible speed.- in less than ideal situations I see about 1A output, so then I choose, I plug in the most discharged device.- if my devices are fully (or mostly, >70%) charge, then in weaker sun I would probably be best recharging the most discharged device, or the most important device (phone first, then tablet).- in strong sunshine, if I my devices are mostly fully charge, then I’d plug in a 10000mAh Powercore to make use of the energy to story to carry me through any future wet / less-sunny period.- I find an average of 5Wh to 10Wh/day is realistic from solar, then look at your devices and calculate. The Moto G4 Play in an off-grid situation its 10Wh battery and lasts me 2 days (phone needs 5Wh/day) so you’re talking even in a sustained bad weather period, a few days worth is valid, and then weather turns better and “too much energy” to which the 10000mAh soaks that up then handle the next rainy days, repeat, so pretty much can be off-grid indefinitely.
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This is what I want to do! I completely agree [quote=“nigelhealy, post:10, topic:54340”]
Buy a USB testing meter, they are far more reliable information of what a device tells you, because most devices, when you turn on the screen, to operate an app, they reduce their input due to thermal throttling, so the figure you see is lower than true. You don’t necessarily need to take the meter with you (but they are light and small so why not) but if you spend a few days learning your solar / device interaction at home, it really helps when off-grid, to make best use of your solar budget.
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Okay I will take a meter to better understand the behavior of my devices and the solar panel considering on the climatic conditions.
Thanks!
iphones are the least tolerant of solar’s variability, if the sunlight reduces then increases, iphones often lock themselves to a lower trickle charge and you have to unplug and reattach the iphone. Android is more tolerant.
Some solar panels detect they are connected to a device not taking all that is available and reset their output, the equivalent of unplug reattach. A meter would let you see if it is happening.
Use of a buffer battery helps get around this.
The 3rd video begin watching at 7m15s and see how Apple products interact with variability and how the meter informs.
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That’s why people says to connect to the solar panel a power bank and then charge the iphone!
Many thanks now is all clearer
Correct, it is more consistently reliable. The problem with this is you potentially lose energy as to charge a Powercore then it recharge an iphone has some power losses in the in/out process. Or you get power wasted if an iphone is locked at a low charge. Best to learn this at home with a meter. I don’t own iphone, but I do own the Anker 21W and a USB meter so I could test to see if the Anker solar panel resets itself possibly if I could borrow someone’s iphone.
Still is recommended to keep the solar panel in the sun, propped to be at show its maximum visibility to the sun, and a sufficient;y long cable to have whatever it is charging lower down in shade, e.g. solar propped on a backpack with the Powercore on the other side in a dry shaded spot.
I see you own 10000mAh, the problem is it is a 2A input, potentially in strong sunshine you’d have excess solar energy that Powercore cannot soak up, also if its nearly full anyway. In that situation something like the Powercore 26800 or Powercore II 20000 (I think renamed the Elite) is dual 2A input you use the two outputs of the 21W panel and it then can take more of available energy, but obviously at added weight. Or plug in Powercore 10000 and the iphone.
Hi there!
I finally bought a 20W 3A solar panel (I do not know if I can write the brand).
I tested it a bit during the wonderful september sun and it works really well! It charge my iphone 6 in 1 hour and 40 min against the two hours with the standard apple wall charger. The Anker power core 10,000 mAh is full recharged in half day. Pretty impressive!
One thing I noticed, however, is that there are continual power outages during the charging times. To make an example during the charging of my iphone there were about 40 power outages, and immediate reboots).
Why is this happening? I think this power outages can damage the battery of the devices.
My panel has a feature called “Automatic Restart”: “Don’t worry if the panel is out of solar power, the charger panel will automatically restart charging when it is illuminated again.” but during charging time the panel was all the time in a wonderful direct sun, never a shadow, never a cloud.
Do you know why these power outages happen? Will it be a factory defect?
Thanks in advance!
Yes, solar is surprisingly good these days, powerful and compact, relative to the technology only a few years ago, newer solar technology is more efficient and the cost is dropped.
So the problem:
- Crapple is notorious for when seeing a variable current / voltage input, it locks its pull to the lowest it sees. So a passing cloud causes a permanent reduction in recharge until the cable is pulled out and put back in. Solar output varies on many factors including heat.
Workaround options:
- the solar panel totally disables its power output many times particularly if the solar energy lowers then goes up. This does not break the phone, it is an unfortunate required hack for Crapple’s obtuse weirdness. Even if the solar energy is constant, if the device is not pulling the energy available, the panel will reset to try to encourage the device to pull more.
- do not connect the Crapple product to solar, use a battery to store solar energy then later use that battery to recharge the Crapple product. This is what most Crapple owners do with solar. Also regardless of make/model most devices you would be off-grid using would struggle to use all the solar energy. The issue is that strong sunshine is “too good” for a typical phone, in strong sunshine you’d often see 2A output but a typical phone is only capable of pulling 1A-1.6A anyway and a typical phone will vary its pull based on many factors such as if you touch the phone it increases its CPU/GPU demand which causes heat in the phone so the phone reduces its heat by slowing its recharge of its battery. The issue is the solar panel does not know why the demand is varying or less than being offered, it does not know if due to Crapple device or not, so given Crapple obtuseness exists, the solar panel keeps resetting its output port. If Crapple never existed, the solar panel would never need to do this. If the sun is strong you are discarding solar energy with a typical phone of any make/model so in strong sun you can instead use a battery. A good battery option is the 10Ah two of them, or the Powercore dual 2A input to take collectively all of the 3A output.
- don’t buy or use Crapple. Save money and buy Android instead. When I’m off-grid for long periods I use a minimalist basic cheap Android phone because when off-grid I’m more likely to have an accident of the type which can break a phone, the lower-end phones consume less energy so last longer off solar energy, and so these complement each other perfectly. My off-grid phone has a replaceable battery and I carry a spare as its physically smaller/lighter way to store up energy for sunny days into rainy days. An Anker battery pack is much larger for a given energy than a phone spare battery.
You could obviously have a bad product, if you have concerns contact the seller. The constant resets you can see here:
Do the benefits of this outweigh the negatives for chargers that don’t have as advanced technology as Anker?
Don’t understand. Are you asking who makes best solar product?
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No, I’m asking what the benefits are of what Apple does: seeing a variable current / voltage input, it locks its pull to the lowest it sees.
So are you saying that power outages only occur on apple devices?
I will test with an android smartphone to see if that really is so. But I remember that even on power core 10,000 mah there have been power outages. Obviously I talk about sunny days, zero clouds and just one device plugged in (not two) during tests. We’ll see.
Not here to talk about the best phone.
I contacted the seller to see if these power outages is a common problem or an isolated case.
On monday a friend lend me a meter, so I can achieve more precise information and see the resets.
Thank you very much for the information
PS: I just noticed that power outages occur every 5 minutes while charging the iPhone, what could mean this timing?