There are at least two different boards I am aware of. I've not used the one you posted so I can't comment but I know the board in my post #277 works fine. I've looked at each IC and the circuit and understand why there is not glitch when power switches from/to battery.
One issue I've had is at a little over a year, the 18650 went belly up. Open circuit no energy.
Looking into it the life of the lithium's is reduced when"
you charge continuously above 80%. So this board running at 4.2 volts 100% of the time is not the best case.
The batteries like to be "worked" sitting at 100% and seldom if ever being discharged even a little is not the best.
For now I'm just going to change batteries at 10 months or so. I'm looking into a solution but it's not a high priority.
The one i bought was from the link in your post. That's why I was posting as a public service announcement to let others know that the vendor has changed what they are shipping. Even the picture in the store link is different than what they sent. Maybe i will send them a message and see if they still have any of the other ones as they are pictured.
I found the version I had became hard to find. I think when whomever makes these boards makes a "LOT" of boards. The seem to be selling from numerous ebay vendors. And when there are all sold... their gone for good.
However I was recently looking for something and came across these boards on a vendor site I felt could deliver them. However I don't recall where.
I did find this link on Amazon It's still only going by the provided photo but at least you can return it to Amazon. Or you could ask the vendor before purchase.
Found this on Amazon looking for a longer run time. Cost is about 20USD. It takes 2 x 18650 cells and appears well made. It has a much higher charge rate and I observed output up to 2 amps(not that we need that) and it charges quickly compared to the single cell version. I'll be testing it and posting more results. https://smile.amazon.com/gp/product/B09QKJTQKJ/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Okay, so I let a C7 hub run till the batteries were dead, it was 24 hours run time. It seems to me, based on casual testing, that the circuitry in this 2 cell version is less efficient than the single cell version, which ran for over 13 hours IIRC
Rookie mistake, I used 2 high power Samsung 18650's(3000mAh) versus the 3500mAh panasonic cells in the single cell version. If I can find 2 newer panasonic cells I'll retest with those.
Looks nice. For 20 USD the Pi Power seems to be an economical solution, although I like the design & battery handling of the device you linked.
I'm still using 3 of my intial sub 10$ solution. The power has only blipped once since I implemented the UPS, and the board kept things running easily. I've had to swap out 2 of the 18650's as after being charged for 3 years, they're worn out.
Honestly if you put this in a store let me know. I would jump on this. I honestly haven't jumped on something like this yet because it seems so hit or miss on a good solution because of weird supply of the parts.
Just read through the description of the device, @rlithgow1 ... can't pretend I understand all the tech, but he does seem to hit on the right issues and like his methodical approach/description very much. Mark me interested!
I agree, the design appears to be a proper "USB UPS". It's also designed to use LFP batteries instead of NCA/NMC so the batteries won't mind being charged to 100% and discharged to 0%.
I've never been happy with the quality of the Bangood units, half of the units I got didn't even work and several required the micro USB connector to be re-soldered so they didn't break off.
Cool store...makes me wish I still had access to the Tandy one of my neighbors had many, many moons ago. I really didn't understand it all too well at the time, but he was a gear head and had so much fun w/it.
That is not uncommon! 
