Yea, I know I was talking about large installs of 100+ batteries in a pack. Mostly done as diy powerwalls or off grid solar, but has a niche fit in network closets.
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Yes, and yes. Sorry I didn't reply sooner. For some reason, the reply arrow hasn't shown on my PC for months...until now, of course. If you tried it, I hope you used electrolytic caps and observed proper polarity. 
I did validate polarity. Used a single 470uF and no go. I have a 1000uF-35V-should I try?. I'll assume the voltage doesn't matter, as long as its rated above 5 volts??
Thanks
Has anyone lately been trying to print out the 3D print enclosure mentioned earlier in post? I downloaded it and in slicer it looks like some of the holes and walls are missing a bit of perimeter.
I'm using PrusaSlicer.
There are (at least) two different versions of boards with this basic functionality.
The first one (the one I am familiar with) has three IC's. They perform the following functions:
- Battery Charge control
- 3.7 to 5V boost converter
- over/under charge protection.
In this design the load (Hubitat hub) is always powered from the battery. When mains power is available the battery charge control will replenish the battery. Therefore when mains power is lost, there is not output "glitch" as the hub remains connected to the battery.
Three IC's: Battery Charge control, 3.7 to 5V boost converter, over/under charge protection.
see posts 1, 91 & 102
I've been using this board as a UPS backup for many months with no issues.
On the boards with the single 32 pin IC (PN SW6115) the load is not connected to the battery but is controlled by the SW6115 controller. I don't have this board so I cannot tell how long the outputs go off then mains power is lost. But apparently the amount of time of the disconnect exceeds the hold up time for the Hubitat hub.
All the technical information is in Chinese so I haven't been able to see if the lag in connecting the battery is specified or controllable.
One IC:
QFN 32 Pin PartNumber: SW6115
see posts 218 and 296
SW6115 IC:
Used Cura & got from thingiverse, no missing pieces
The 1000 at 35V should be OK and theoretically should provide additional "run time" once charged. It only needs to do it's job for a few milliseconds, so I really can't see any reason why it's not serving its purpose. If you want to get really juicy, try using two Super Capacitors - 10F/2.5V wired in series. (about 2 US$ each) Those should theoretically run HE for minutes without the batteries being installed. (I may have to try that just to see...)
If you do try two supercapacitors in series you should consider something to insure the both charge and discharge the same. Else yo will find you might have 3V on one and 2V on the other.
You and or @JohnRob might understand better than me. with the cap properly installed it made no difference. I'm thinking, could it be possible the chip will only engage the battery once the voltage drops beyond a set point, at the USB voltage terminals? I say this because I know the cap works, yet there was still a delay for the battery to kick in even with the cap installed. Anyway don't drink and solder, as I killed the board by putting in my helping hands alligator clips and thought I had taken out batteries, but I failed and the metal alligator clips shorted the board and... Magic smoke.
Project over
Alas, once you let the smoke out it's never the same.
Do a search for pi ups hat on Amazon. I'm sure you'll find something that suits your needs for a quite reasonable price. For example: https://www.amazon.com/MakerFocus-Raspberry-Standard-Expansion-Cellphone/dp/B01LAEX7J0/ref=sr_1_4?dchild=1&keywords=pi+ups+hat&qid=1610253772&sr=8-4
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If anybody in the UK has a 3D printer and fancies printing me a case I will happily ship you a good quality Samsung 18650 battery in return. Heck I can ship you two batteries if needed as I do have a few spare from a previous project.
Got my version from Aliexpress arriving in a few days hopefully and will see which version I get (so much stuff of Aliexpress doesnt match the website), so can definitely experiment with capacitors if I get one with the 32 pin IC.
Not as cheap but Monoprice has a USB Power Bank that can charge and supply power at the same time. 20,000 mAh for $25.
https://www.monoprice.com/product?p_id=15120
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They look great. I would buy one now if I knew the device could charge and supply current at the same time.
Some time ago I eMailed Anker asking if their power bank could charge and supply at the same time. They responded "no". Their explanation was that a peculiar condition existed where it was not (reasonably) possible for the device to know what state the power bank was in.
So if you purchase the Monoprice and it works for you, please post back what you found. I would love to purchase one of these for USB backup.
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+1 Iād be keen to hear if it works properly too.
Based on answers in the Q&A section on the site, it seems that it will charge & feed simultaneously.
Hmm, this is tempting to try... I'll think about it.
There is no think, only do ..... 
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UPDATE
I saw the Q&A answers on their site also saying it passes through power when charging. I have one 10,000 mAh that I bought a while ago mostly to charge cell on vacation.
According to the documentation that comes with the power bank:
"The LED indicator will blink while charging"
So I did a test:
I plugged a hub into the Power Bank with the power bank plugged into a wall charger. The hub powers up and the power bank LED still blinked like it's charging. So apparently it does charge and pass through power at the same time BUT,
When I unplugged the power bank from the wall charger, everything goes off. I had to push the button on the power bank to turn the juice to the hub back on. DOES NOT automatically switch from charging mode to output mode when the power goes out.
So much for use as an automatic battery backup. 
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Bugger! 
Cant say Im surprised tho.
Even if you find one that can charge & supply power at the same time, That will not always translate into a smooth transition from wall power to battery. The last device I had did just that, it would pause for about 1 second when switching from wall to battery power. It was a 2 cell version of the one in OP, with different circuitry.
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I think this is the nature of the beast. At least without extra circuitry$$. I'd guess the market for UPS use is so small its not worth the cost addition to every device they sell.
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