oh wow. that means in Summer you could charge up a 10Ah Powerbank in one day with that module.
That’s really nice.
How about not direct sunlight - just bright outside - does it produce 5V or not?
Blitzwolf BW-L1 20W solar panel with BW-L1 code is now 6$ cheaper. It’s basically a rebrand of Anker 20/21W panel (I’ve seen it called with those two watt designations) - this one: Anker PowerPort Solar . There are some reviews online for Anker but basically it’s same quality as 15W sibling but delivers more current. It charges 10000mAh Xiaomi powerbank with ease in one day even without strong direct sunlight. 15W version seems exactly like Anker PowerPort Solar Lite. Blitzwolf/Anker solar chargers offers incredible value for the price and you will have hard time find anything better out there for twice that price. Anker is slightly more expensive so Blitzwolf with free shipping is no brainer. Blitzwolf 15W solar panel goes for $32,99 and if you have enough BG points you can even drop that to $28.04.
Those AX panels are way overpriced for their performance and low quality cells. Blitzwolf says it uses SunPower cells with over 20% efficiency and performace seems to support that claim. Not to mention the fact you can fold Blitzwolf cells and they are very convenient to carry.
Regarding the question about charging in indirect sunlight - I did not measure the voltage, but if the sky is overcast and still overall bright or the panel is in soft shadow both smartphone and Xiaomi powerbank are being charged but of course at much lower rate. 20W panel can even charge inside by the window. Those SunPower cells are excellent for less-than-optimal sun exposure.
You may want to venture into something more “wide range” and sophisticated. Take a look at these modules:
- B900W NC DC Constant Current Power Supply Boost Module Ammeter
- 400W DC Converter Boost Step Up Power Supply Module 6-40V to 8-80V
- DC-DC 600W 10-60V to 12-80V Boost Converter Step-up Module Power Supply (seen $1-2 cheaper on eBay too)
These modules have wide enough voltage range as to safely accommodate and use effectively multiple in-series solar panel arrays (at least as that one you mentioned).
Do the math. The expensive first one should safely manage a 7SnP setup, and allow it to work from a really low per panel voltage (<0'9V). 
Hope this helps. 
Cheers ^:)
I’ve been thinking that the BlitzWolf and Anker solar panels were ‘related’ for some time now. Nice to see it corroborated.
I’ve been doing some testing with it, to write a post for my blog.
But surely that 20W is theoretical.
They state 3A output max, so in my book that’s 15W max (because of the 5V it puts out).
I have yet to make a timelapse of a full day on the two outputs combined, but in one day of sunshine (a norlal summer day, not that burning sun) you can recharge 2 10.000mAh powerbanks, even when it’s a bit cloudy.
I did a review for “Archeer” of a similar solar panel.
3 panels (15watts) and 2 USB ports.
I was able to draw 1,8A on both ports in full sunlight.
Output is falling with clouds apparition obviously.
I have 2 and 3 
I just hooked up my DMM directly to the solar Panel - it went up over 17V without direct sunlight.
I think, the main Problem is the current and what the Buck/Boost eats from that - if that is too much, the voltage drops too low for the circuit to be able to boost it up.
Why I “need” (want) a solar Panel:
I am planning a part-time-camping tour through Norway and Sweden - half of the time in a tent, half in privat rented rooms.
I just need something to charge my flashlights and mobile-phone - both with one or two powerbanks as temporary storage.
Made a new video to hopefully show the performance under cloud cover and in sunshine :
This was a proof of concept-test for a whole day test up next…
Great video, thanks!
I will buy that 20W thing when I need it.
New vid : one full day of sunlight…
I think I’m done testing it now. Which is a good thing, because RAVPower sent me a bigger 24W solar charger
Nice videos. Thank you
> RAVPower sent me (link is external) a bigger 24W solar charger Wink
Yikes!
If your family’s asleep, turn your speaker volume WAY down, before clicking that link.
What’s the real maximum power of BW-L2 (15W)? Based on video 7W, well that’s not so bad but not perfect. I would prefer Poweradd 14W, Kingsolar or Solarkingdom (13W) (amazon) similar panels rather than BW. I managed to extract 10W from such type of panels. Smaller pieces of cells is a real disadvantage because during the full cell cutting, micro cracks appearing that reduces output power.
I found this helpful.
Not really man, not really. There wasn’t a single panel that I mentioned before. All this stuff is the old one and do not worth any attention. May be someone will find it interesting, I don’t know. First of all a decent one solar panel must be made from Sunpower cells.
No, there was mention of your concern, but I find an abundance of information helpful.
Could you explain or clarify, what exactly is supposed to be useful? Especially for the users, who’s looking for a good portable panel. I might be wrong and gonna change my opinion.
There’s an unreadable picture of a comprehensive spreadsheet in that second video.
Where can we see the actual spreadsheet?
Seriously, text is far more useful than videos for making thoughtful comparison of multiple items.
For one, claims made by many solar products are false, and I found it helpful to understand how solar power is actually achieved to power up power banks.
If you are looking for quick answers on what solar panels to buy, you are an ‘easy touch’ for false claims and assumptions. I was only trying to be helpful, but it was my false assumption that I would be helpful. 
I agree with you about preferring text information, but I use what I can find.
For the spread sheet information, I went to full screen and stopped the video and enlarged text or font size.
The main thing I learned is that not knowing the science behind solar energy for powering power banks leaves many of us with a vulnerability to half-truths or even false claims.
Being a smart consumer does take effort, and people trying to sell you stuff only want you to know their POV.
It’s obviously, I’ve presented a piece of information with some recommendations which based on my experience and topic understanding. I’m ready to sign under the each word. Forums have the same reputation as youtube, you decide whom to trust.
Theory or physics of solar panels is much more useful for the beginners as a main source of information. There’re many different solar panels on market, their main disadvantage is weak electronics. That’s why I solved this issue by myself. SWIFT Solar Wide Functional Headlamp, developing and discussing.
Yes, sometimes I got tired explaining all basic things from the beginning again and again on my previous forum. So, what I wanted to say, the best way to get knowledge is reading books or articles.
My apologies if something went wrong, I’m still adapting to a foreign language, this’s my 1st day on this forum. That was my personal point of view, who am I to judge.