Indeed the original 26800 dual-input remains one of the best choices, as 3 ports out which suit most things you’d travel with and yet recharges off solar and in rapid time for its capacity.
But if you’re buying for real life, a mix of performance and capacity, a sale on the 20000 PD 18W input is still the sweetspot.
Discounts been infrequent and low for months, Covid…
Yeah I still have the one Anker sent us and it’s working great so far.
Well I’m in no rush to get a solar battery, just wanted to dio my toes into solar charging but I’ll keep my eyes open for a GOOD discount
Avoid anything with small solar panels as utterly useless hype. The Anker 21W is good, and probably the Anker 24W should be good but this thread suggesting dud doesn’t help.
Until there’s mandatory quantum physics, mathematics, for all buyers, just have to stick to simple terms.
You know the electrons from a solar panel now are given their kick out of silicon atoms, made from photons which were made about a million years ago from atoms made about 4.5B years ago? The photons you are reading this by were made a tiny fraction of a second ago, using chemicals in you eye made from what you ate yesterday.
I’ll keep those two on my list of “Things to buy that I don’t really need” 
Just as a final update, we now have some seriously nice weather; pure sunshine from 8am to 9pm which is fantastic.
So I’ve tested the powersolar on 3 separate days and it performs exactly as I hoped, it charged up my 65W 20,000mAh power power bank in a day with nothing else attached.
With cloud, it does have a temperamental ‘off/on’ attitude that means it supplies a charge one second, and then stops the next. This seems to be mostly when the light is near to the minimum threshold for an output. For this reason, I decided not to charge my phone on these days, but instead charge a power bank with pass through.
In response to iPhones being problematic with the charging setup, I can’t say I’ve found this issue at all? On the sunny days, the powersolar charges and the phone takes the charge without any complaints so this is good news. I’m using an iPhone 12 if that makes any difference.
I expect the performance will change depending on solar intensity/season/latitude etc but I didn’t buy it as a replacement for an AC mains charge, which I wonder might be some of the reasons for some people returning the item? I know and accept the output will be a fraction of a mains charger!
The important bit which relates to my OP, is that it seems the red circle is BOTH an indicator of electrical incompatibility with the device AND an indicator of insufficient solar input to output a charge. This isn’t mentioned explicitly on the instructions and so I think a lot of people might assume there is a problem with the unit when it is actually just isn’t getting enough light.
All in all a great buy for those outdoorsy people away from a mains charge 
Sounds a happy outcome, and the manual needs updating.
There’s threads from years ago that iPhone stop charging when receiving variable power and so a buffer battery charge it and it charges phone was the answer, and Android phones more forgiving and so charge direct.
I’d still recommend buying a usb meter to debug all the types of issues like dud cables.
when you put your item in full sunlight then the red will be blue.