20 watts ensures that the UPS can both, power the hub and charge the batteries at the same time in the event of them being discharged.
The UPS will always prioritise power to the hub, and will use any left over capacity to charge the batteries.
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I will be very curious to hear from those in the US that get these first - I was very slow in paying!
Set it up, let it go for a while then see how much charge in the batteries.
What my research is showing is:
A) The two chargers linked by @djos are not available in the US anywhere. Neither of them list any modern power profiles on their product sheets (PD or QCx)
B) Any USB-A charger that is available in the US and offers more than the 5v@1a all come with the marketing for PD, or QCx. Per the notes above. this device will not trigger those charging profiles. Therefore you will get juice at the 5v@1a. I think that is within the range to power the hub, but that leaves nothing left over for the UPS.
Curious to hear results. I too have a bunch of charges and will try things, eventually!
Fun!
18 watts is close enough and they seem very common on Amazon.
USB C Wall Charger Block 20W, 2-Pack Dual Port PD Power Delivery Fast Type C Charging Block Plug Adapter for iPhone 11/12/13/14/Pro Max, XS/XR/X, iPad Pro, AirPods Pro, Samsung Galaxy and More(White)
Re: what adapter to use.
If Rprog (R14) is still 2k then the charging current is limited to 1 amp. If the Hub needs 1 amp (I think its really something above 650ma) then a 2A adapter should be fine.
In general switching supplies are most efficient near their max capability.
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FWIW the thread for this design started on post # 290. So we've had 450 posts 
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The USB-C spec defaults down to 5v when the resistors for detection are not present. The resistors are really needed for the USB C PD detection. The Insignia supply i have is stricly 5v 3amp only so no negotiation occurs at all. It is basically a dumb power adapter.
The Splanks adapter you linked can do 4.8 amps across all porta but maxes at 2.4 for a single port. The USB C adapter goes up to 3amps when running at 5v.
As @JohnRob pointed out if the power shunt is the same then it will only ever charge at 1amp at max anyways.
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Yep, and this version of the ups isn’t USB C compliant, hence my recommendation to use high wattage USB A chargers. 2.4amp (12 watts) is ok, but I’d recommend 18-20 watts to provide safety margin.
I’m just waiting for my cygnett 2 port 20w adapter to arrive before replacing my 4 port unit with it.
The 4 port unit is my travel Charger that I used temporarily when I discovered 5 watt adapters weren’t adequate.
We should keep in mind the UPS using the TLc4040 in not USB-C compliant. To my knowledge the USB-C connectors were chosen because they were thought to be more robust.
I recommend a plain old 5V 2A dumb adapter that's UL approved. There is no need for the smarts and complexity of a "fast charger".
For me UL approval is a requirement to be used in my home. Others may disagree.
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I understand the desire for headroom. My point is you they don't make usb a or usb c chargers that go over 3 amps when doing 5v on a single port. That is 15 watts at most. When you point out a charger that is doing more it is a multi port charger that splits the max load between to ports.
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That’s not entirely true, the good quality units, like the cygnett I’ve ordered and linked to above, can supply 20w per port and 15w at 5v.
- USB-A Output 3: 5.0V⎓3.0A (15.0W), 9.0V⎓2.0A (18.0W), 12V⎓1.67A (20.0W)
- USB-A Output 4: 5.0V⎓ 3.0A (15.0W), 9.0V⎓2.0A (18.0W), 12.0V⎓1.67A (20.0W)
Right but for those to reach 20 watts they need to use 12v. I thought this ups only allowed 5v input?
Yes, sorry i really should have been a lot more concise with my rationale.
I mainly specified a 20 watt charger because they are almost guaranteed to output 15w at 5v.
You are correct, this ups is a 5v device.
I think you guys are over thinking this. The LTC4040 limits battery charge to 1 amp (5 watts). The Hubitat hub varies between 0.2 X 5v = 1 watt and 0.65 x 5V = 3.25 watts.
A 5V 2A supply will have 17.5% headroom when the Hubitat is at max current (which is not often).
Also remember the charge current will taper off to some milliamps when the batteries are fully charged (which will be 99+% of the time)
Any decent supply capable of 5v / 2A will be more than adequate.
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I've been a lurker in this thread for quite a while. I took a break from it for a few months and was blown away at how much activity had occurred. I'm back now because my cabin had a 13 hour power outage where my standard UPS completely depleted and shut itself off. Of course when the power was restored, my UPS stayed off and now my Internet and HE hub are offline. I should add that my cabin is an 8 hour drive, so it's not a simple trip to press a button.
So here I am with a few of questions.
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Is there 1 board, with case, still available?
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Am I correct in thinking that if this battery backup were to completely drain, before the power was restored, when power is restored would it power the hub back up? Basically not be stuck in an off state like my current UPS?
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I'm assuming I need to supply my own batteries for this backup too?
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From question 3, I've heard stories of some batteries being more unstable and/or more prone to catching fire. It's a family cabin that was built by family 52 years ago and I don't want to burn it down. What brand would be safe and good for longevity? Both in runtime and life itself. I winterize the place so the lowest temp could be about 30°F with the highest being 85-90°F in the summer.
Thanks in advance for the help
You are correct, I guess I’m just trying to avoid any issues by over specifying the power supply.
I think sold out, I’m just waiting for confirmation for the last unit.
Correct, they use 2X unprotected LifeP04’s in 18650 format.
Yes, that’s exactly how it works.
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Bummer. I'm going to DM you my email address just in case that confirmation doesn't come through.
Are there plans for another batch?
Any fears or Hazzard issues with these? Overheating from over charging or swelling?
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No, it uses the rather expensive LTC4040 power management chip and I’ve configured it to operate between 20/80% of the battery capacity only.
Plus LFP batteries are a lot safer than traditional lithium ion.
Not I unless I get time to improve the design (make it easier to build) and fully USB C compatible).
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I was thinking that your v2.0 model could be the same foot print as the Hub ( to act as a holder for the hub) with the ability to hold 2 or 4 batteries with a key way lid of course 
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That’s a pretty good idea! I’ll definitely give it some thought.
I was also thinking about including a Zigbee radio to communicate battery State and power source status.
That last one is defiantly a stretch goal for me.
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