Hard to believe USB-PD upses aren't a common products.
There's no reason anymore that a power bank should ever even have an off mode unless it's so cheap there's no passthrough, which shouldn't be a thing either because it's annoying and probably saves 50 cents.
It's microamps with a good eco mode switcher.
Inline USB ultracapacitor banks seem like a reasonable product too though.
Hopefully USB will give us standards for power banks someday so you can get certified ones with a defined form factor and behavior.
Yes, but between Revision 11 and 12, all manufacturers on the consortium unanimously voted to up all voltages by 0.4V to increase incompatibility. Still the same gbps though.
There's something sort of horrifying in the fact that I can't tell if the posts in this thread are real ... or fake in pretending to be a bureaucratic, ridiculous joke.
Anker has a power bank with integrated charger[0], or charger with built in power bank. Don't think it's made to be used as a UPS, but maybe it can be.
> Inline USB ultracapacitor banks seem like a reasonable product too though.
I actually saw just that in a GreatScott Youtube video about Aliexpress gadgets just the other day[1]. Not sold as a UPS, but rather a power filter or buffer.
Laptops can run off of any USB-C power bank now, so it's no surprise there's no market for something like this. Cool product though!
It's on the line voltage side like any other UPS, so not as efficient as you could be with a solution that didn't have to convert AC to DC then back to AC then to DC again in the brick. But with Apple's proprietary charging connector soldered to the device end of the brick, what else can you do about it?
Exactly, even 5000mah in your standard USB-PD 60w adapter would be a huge boon, especially for laptops where the internal battery has begun to fail and replacing the battery means replacing half the laptop, app..cough..le
> replacing the battery means replacing half the laptop, app..cough..le
These kind of comments are surprisingly common on HN and annoy me slightly.
Yes, most phones and laptops do not have user replaceable batteries anymore. It's a pity. That does not mean a dead battery is a justification to throw away fine equipment.
Any phone repair shop or computer shop can replace batteries. They usually have all the equipment and spare parts, even more so for popular Apple devices. It usually takes half an hour and costs way less than replacing the whole device.
I always recommend that to friends and family because most of them are not even aware this is possible. They usually thank me later saying how painless and affordable it was to give a second life to their devices.
I did not say it's justification for throwing away old equipment, but at some point, the high cost of replacing a battery (high because it requires a 'repair') offers less value than buying a newer model. This is especially the case with, say, Apple laptops where the official battery replacement means the entire top-case and keyboard has to be replaced.
A good way to keep these devices in use would be with an external battery, and one built into the power adapter would be very convenient. Just an hour of power would be enough to move around to meetings without multiple reboots.
I just did a battery replacement on a 2017 MBP. While there were a lot of screws needing to be removed and lots of lifting/prying to get to cables, half the laptop did not need to be replaced.
Assuming the default failure mode of the battery is degraded capacity. Over the years I've had an alarming number of lithium-polymer batteries puff out in consumer devices ranging from my Dell XPS 13 (9343 model, battery was replaced three times) to the Moto Z Play phone (dislocated the screen, replaced twice by Asurion, third time they claimed it was a warranty issue and played support tennis with Verizon) to an iPod
Touch (also popped the screen out).
For some reason I still cannot fathom, the 50-cent saving is a point of great pride to electrical engineers. They repeat some phrases about million-unit manufacturing runs and I just seethe with anger that we can't have nice things.
Good case study for Harvard Business School. When a design engineer wants to cut a feature to save a few pennies, they are teamed with a marketing pair-analyst to assess the TAM and margins, considered holistically with other feature subsets.
> 50-cent saving is a point of great pride to electrical engineers
As an engineer you are given a power budget, a thermal budget, a size budget, a weight budget and a monetary budget, among many other constraints. This means, like any engineering endeavor, there are tradeoffs to make. That 50-cents you saved on some power controller might be "spent" somewhere else that has a higher impact on the product.
There is a near infinite set of things you can do to make the product better somehow. Unfortunately you don't get to do them all. Many of the things conflict with eachother--more battery life might mean more weight and size that you have to "steal" from some other aspect of the product to balance out. Faster, better charging might cost 50-cents but that might mean in order to stay on budget you'd have to use a lower quality plastic shell that is more prone to damage. That faster, better charging might also eat into your thermal budget, meaning you'll need to spend more on cooling, weight and size.
I imagine it's a similar feeling of pride felt by the engineers who design outdoors equipment that only fits in the provided container when folded precisely how it was at the factory with no margin for error.
I was amazed when I learned that most powerbanks do not function that way. Some of them will switch modes if you unplug them, but there is still an interruption.
It is so nice to be able to unplug my Pi to move it, and have it stay on. I also use them for my usb powered wifi security cameras. So far they have not failed me.
> Hard to believe USB-PD upses aren't a common products.
Insanely easy to believe. The role of UPS is to prevent data loss when power fails. If something is powered by USB-C it almost always already have its own battery preventing from that.
The only devices that are not are stuff like say, raspberry Pi
Also, there literally are devices like that, just aimed more at stuff like camping, so much bigger battery, usually an inverter on board and solar input.
> Hopefully USB will give us standards for power banks someday so you can get certified ones with a defined form factor and behavior.
If it will be like USB-PD then it will be insanely overcomplicated and nobody will be able to get it right.
> The role of UPS is to prevent data loss when power fails. If something is powered by USB-C it almost always already have its own battery preventing from that.
That's a very narrow minded approach to both UPSs and items using USB as their power plug imo.
A UPS isn't just "to prevent data loss when power fails." It's also to keep critical (for home, not DC) things running in the event of power outages. Current uses for USB-C power banks as UPSs I have (or have recommended to friends) that aren't "to prevent data loss".
- Power bank running as a UPS on (a few critical) wireless security cameras (that use USB-C for power).
- Power bank running as a UPS on my cats water fountain (uses USB for power), if the power goes out she still needs to drink water, and I may not be home to put down a standard bowl.
- Friend has a baby monitor and took my idea of using a USB power bank as a battery backup on the camera and monitor so that if his power goes out he can still keep tabs on his child. (no sense waking her up to move her if he doesn't have to)
> Insanely easy to believe. The role of UPS is to prevent data loss when power fails. If something is powered by USB-C it almost always already have its own battery preventing from that.
That's a moot point though, IMO. Like if you're travelling, wouldn't it be nice if your charger and your battery bank were the same device? Just because it doesn't have the same specific utility as a UPS, doesn't mean that it's not useful in other ways.
There may be a market for an ATX USB-PD power supply. My desktop has no spinning rust nor discrete video card. A 60 watt power supply could power it easily, especially if there were a small lipo for the occasional burst.
Solar generators aren't specified to be UPSes. Some work, some don't, just like power banks. I love them, but they're not always perfect.
Raspberry Pis are common though. They've taken over like half of DIY electronics and home servers, for a good reason, everything else is way more hassle and less supported.
Not sure why you say PD is overcomplicated. Until you get above 30 to 60w where not everything supports it, stuff just works. Their only big mistake I see is not keeping the 12v power tier.
WAY too many things run on 12v and losing the ability to easily run legacy stuff sucked. But they'll fix that when 12v PPS trigger modules are available, for some reason they are not currently.
Get a 12V SLA battery, solar charge controller, 14-20V AC adapter, and a USB car charger if you need 5V output in addition to 12V. DONE!
The "DC UPS" units you can find for sale (as well as USB power banks) don't have any monitoring/data connection. Real UPSes have them to tell your systems to perform a clean shutdown when the battery gets low. Since they're all just simple dumb batteries anyhow, you might as well roll your own for less cost and much more runtime...
To make it a proper smart UPS, you would just need to add a low-voltage trigger that talks over USB, RS-232 or Ethernet. Something like a 12V relay could act as a "contact closure" signal, though you'd have to test the cut-off voltage and perhaps try a few different values of resistors to fine-tune the low-battery signal.
Why over complicate it with electronics? It’s a computer.
Just have your device shutdown when it can no longer poll another device. For example, if the router or some other network device isn’t contactable for longer than two minutes, it might indicate that the power is out.
The router is one of the first things I put on a UPS. The telco equipment likely has fallback power as well.
Sure, you could find some device that isn't on a battery backup and ping it regularly. But this approach forces the device on your UPS to shutdown as soon as power is lost. That buys you a clean shutdown, but you don't get the added benefit of being able to run without interruption during a brief brownout.
> Just have your device shutdown when it can no longer poll another device.
Most people want their devices to stay up and running on battery as long as they can, not just shut-down immediately after utility power goes down. Without somehow measuring the battery voltage, you can't estimate how much run-time your devices have to work with.
Any networked device will do - switch, router, etc. If there's no link on the port, power is down. USB-C Ethernet adapters with power pass-through will generally power the Ethernet module off the USB-C power port even if no host device is plugged in. USB-to-Ethernet adapters may also light up the port even if only connected to power (and not a host device).
That's not hard to do, for some networked devices that step amounts to just plugging it into a power source and connecting it to the network. I haven't had to touch the configuration of my wifi printer for example since I plugged it in to the wall years ago.
Also a much bigger timeframe for testing and development. This isn't something you slap together in a weekend and call good. More like building an experimental drone than putting together a 3d printer kit or building a PC
No idea what you're talking about here. Solar charge controllers are quite mature and do exactly what is needed. You're literally putting a few wires on the right terminals, and a few connectors.
Only the low-battery signal would require a bit of work, but that is option and isn't found on ANY devices available off-the-shelf so it's not possible to buy your way around that.
Sure the "DC UPS" are basically "simple dumb batteries", but the sort of loads that you'd probably run off them and the expected runtime of each tends to be quite different.
Guessing the average AC UPS that someone might back a desktop with might last 5 minutes (or in a data centre long enough for the generators to kick in). A "DC UPS" running a router or a raspberry pi likely has a runtime measured in hours. Still would be nice to have monitoring info available, but more time for human intervention to shut down if need be.
"you might as well roll your own for less cost and much more runtime..."
Depends on how much gear you want to power. If you just want to keep a raspberry pi online a few hours I doubt you'd save much money (if any) rolling your own. Could be fun as a project though.
I got a large power bank (Bluetti EB55) to get me through the expected power cuts this winter. Supports charging from mains or solar while supplying power. Of course at £900 it's hardly a cheap option ...
If Europe has rolling blackouts this winter, the purpose is to reduce energy, and hence gas, consumption.
If everyone were to charge a battery bank when the power is on, to see them through the time when it is off, the net result would be increased energy consumption, due to efficiency losses.
That would only be true if people are charging huge batteries that sustain their full home energy usage. If they're only charging small batteries to sustain the most important devices in their homes, the usage will still be much lower.
Additionally, peak/off-peak is a thing. The grid may have excess power from wind and solar when conditions are idea. Charging your batteries during those times will not have any negative effects.
There are, however, USB-PD sources that can run from a fixed voltage DC supply.
I would actually really like something like this that can fit in my backpack with just shy of 100Wh (airline limit) of energy storage, a retractable cable to plug into an outlet, and monitoring via USB. In theory, I could build this myself around OpenUPS, but sourcing a pack, retractable cable and suitable enclosure is really annoying.
It is surprisingly not.
I travel frequently with random ESP32 projects in various stages of looking highly suspicious and never get hassled about them. 4oz of an unfinished bottle of water though is absolutely not getting through security.
Do those have large li-ion batteries? Lets say you'd diy your own charge controller, I could see that get treated differently since you could cause a nasty fire that way.
In London security will sometimes specifically ask if you or anyone else has made repairs or modifications to any electronics. Depending on how honestly you answer, this could still be a hassle.
> What's the typical circuit found in a laptop or phone? They all have to deal with this stuff internally.
Most phones and laptops operate at the "micro-cycling" mode that the author describes, it's part of why portable devices regularly end up in the news for swelling batteries. There's no brand that didn't have complaints by people.
Additionally, the power quality of shoddy chargers [1] makes life even worse for circuit designers - voltage ripple or, worse, spikes that rise fast enough to hit the battery... the list of problems is quite endless.
I always see recommendations on /r/HomeServer for using a laptop and I always shudder a bit. I had a battery swell on a Macbook. The thought of leaving a laptop running unattended for months at a time, possibly stuffed in a garage or closet where you won't be watching it for awhile just sounds like a disaster waiting to happen.
The other thing is that if you have a laptop worth using as a server then you have a laptop probably worth selling. Use that money to buy a proper UPS and cheap server and you may even have money left over. You also can't plug routers or cable modems into a laptop, so it's rather pointless anyway.
I have a UPS because I'm hit with short brownouts every summer (yay, California). But if my grid was better and I only saw outages every few years then screw it. Let the server crash. This isn't the 1980s. Nearly all filesystems and databases (ACID, anyway) recover just fine today. Use ZFS if you're truly paranoid.
That depends on the amount of stuff you're running, and how much you care about the UPS working. If the answer to both is "very little" or "not much", I'd take the Pi setup any day.
It also depends on how often you expect to lose power. If that answer is “somewhat often” or worse, then even a minor annoyance can be worth avoiding. There’s a reason laptops used as a server were known as “California servers”. (aka a server with a built in UPS)
I really love the fact that the presented circuitry avoids fully charging the battery cells to extend their lifespan.
SO many consumer electronics intentionally charge lithium cells to their limits to boast long battery run times and high capacities in the specs while severely shortening the products lifespan.
Lithium batteries are awesome, but I think lead acid just makes a lot more sense for a UPS- they like to be fully charged, last virtually forever when maintained that way, and don't require any complex charge management circuitry.
I think cheap batteries, poorly designed starter circuits, and occasional full discharge in use, which all coordinate to damage the batteries early. Also if your power is low quality, it causes the device to switch to battery often, and can put a lot of cycles without actually having a power outage. High quality lead acid batteries in solar systems, car starting, and commercial UPSs often last a decade or longer.
VRLA batteries are commonplace for commercial UPS units. For lithium, I’d explore LiFePO4 batteries. Not all lithium chemistries are alike and LiFePO4 are considered safe. It doesn’t have great capacity to weight ratio but it wasn’t meant for consumer electronics anyway.
I've been a LiFePO4 evangelist for years! I always prefer that chemistry over Li-Ion for IOT devices and recommend it to all my clients. Energy density is rarely the driving constraint except in EV or flight applications
Tangentially related question I'm actually trying to answer in earnest at the moment:
I want to put together an EDC portable Linux box using something like a Radxa Zero or OrangePi Zero, with the idea that it'll run for some nominal amount of time away from a wall outlet.
A power bank is obviously the answer, but I don't want "push the status button and guess at what the 5 LEDs are saying" to be my answer to "how much power is available?". I want something I can ideally turn into an ETA, so that I can then monitor that ETA and send myself alerts when the battery is critically low.
I've found RPi hat "UPSes" that seem to provide exactly this data over I2C... but none of these seem to also provide an all-important enclosure that would ensure I don't accidentally short anything out and literally burn a hole in my pocket. Not viable.
I've not yet explored the world of 3D printing, but I do understand enough to be know that my first 3 or 5 or 28 prints will be slightly janky. :)
So, I'm trying to find a premade solution to this problem - either a power bank that provides Actual Data™ over the USB connection (!), or some kind of devkit-style solution that'll viably/safely fit into a standard enclosure of some kind.
One of those plagues of shitty consumerism & no market pressure: there's a standard that works great but no one implements it, cause they suck & are no good & there's no consumer pressure to do basic shit.
USB HID has all kinds of sensors & telemetry it can do. USB HID includes a whole sub-spec on Power Devices, with all kinds of information that chargers & batteries can report. To take one example, the Battery System Page (x85) can report Current, Voltage, Temperature, Absolute/RelativeStateOfCharge, RemainingCapacity/FullCapacity, RunTimeToEmpty, ChargerConnection, OutputConnection, ChargingIndicator, and CycleCount (among many other factors) to tell you what is happening. You can set RemainingCapacityLimit or RemainingTimeLimit to trigger a USB alarm condition when capacity falls under threshold. You can monitor individual inputs & outputs separately.
(The one ask I have that's not supported by the spec: a StopChargeAtCapacity setting for batteries, so I can stop my UPS's 5000mah battery at 4200mah to extend it's life drastically)
It's a stupid senseless world where the obvious never happens. Consumers aren't educated enough to have sensible asks. What is possible is ignored. I'll try to break out 'lsusb' more in the future when charging, but my impression is that basically no one- not batteries nor chargers- implements the ancient, obvious, sensible, & easy spec for power devices to report the basics about what they are doing. For shame!
I’d also love to see this on power bricks so that I can tell the charger to stop charging my phone and tablet at 80%, regardless of what the device manufacturer gives in terms of software control
I do this with the Home Assistant app on my phone. When the battery level gets to 80% it triggers the smart plug the charger is connected to, to switch off.
My phone is 3 years old now and according to AccuBattery still has a battery health of 2499mAh out of a design capacity of 2700mAh (Based on 977 charge sessions for 1,215,025 mAh total)
I do this with my Android phone using the Automate app (Tasker would work too) and a flashed smart plug. Phone hits 80% charged and it turns off the smart plug. Charger is plugged in obviously.
Seems like you want the charger to be aware of the hosts state of charge. Typically telemetry only flows from device to computer, which this violates.
Most laptops/tablets/phones/&c do know their state of charge & can in software disable charging, although only some expose this to users. This is often available in Linux but I dont think any particular scripts/apps for controlling this have risen to notice yet.
But you are still asking for a complete rewrite of how everythinf works, for it all to be totally different. It's not a totally unreasonable ask, it's just not in reach. Unlike my discussion above, which proposes a plan entirely doable with standards we have.
USB-PD negotiates power delivery, but it doesnt communicate battery or other status. It uses a different sideband to nevotiate outside regular usb communications, and conveys very limited information. There's no battery informatuon conveyed.
My above post spoke to how multi-decade old USB HID standards can be used to present current battery status for battery packs. We'd have to flip the relationship around- make the charger be a host that can manage an attached battery, the laptop be a peripheral that exports it's power status, to invert tbe control system as you want, to make the charger responsible for battery managememt & not the device. Or we'd need to radically revamp usb-pd & layer in a lot more capabilities.
It'd be cool, in some ways. Plug in any device & it'll only 85% charge. But it's also far more complicated & rewrites all the rules in every way, unlike what I was talking about, which is just battery packs & chargers kind enough to export their status over some very very old simple specs.
Yes I agree that my wish is unreasonable and your plan is much more attainable.
I don’t want to flip everything on it’s head (OK that’s a lie: I would love to flip almost everything in the name of having better solutions). But what I mean to say is I know what I’m asking for is unreasonable and certainly unrealistic in a 1-3 year timespan, but I know it’s possible and I like to dream because sometimes moonshots actually land you on the moon
Something like OpenUPS2 [1] seems to provide data over USB, and even has Linux software to support that. It does not seem to have an enclosure though; it's apparently intended to be put into an enclosure of the device it supports. Also, pricey.
Find someone locally who has a 3d printer. If you don't already know how to model 3d objects, they will likely charge you for that time and then 3d print a test. Then when you have it right, there are plenty of pro shops that can produce a more permanent 3d object through Laserjet Fusion or other methods.
They are in no particular order more resistant to under and overvolting, much more cycle resistant, much more resistant to storage under high charge level, much harder to get to explode etc. For UPS purposes they are the correct choice all around-
The title makes me remember my raspberry pi camera I made for my apartment in 2011. I hooked it up to a simple USB powerbank at the time, and then the powerbank to the power outlet. Thinking if anyone cut the power to my apartment it would still record for 15 minutes.
Of course had anyone cut the power to my apartment it would have no way to upload the recordings because I didn't add a 3G failover.
I remember some article of someone trying it, only to discover their power bank cut power for few milliseconds when you disconnected the external power supply, resetting the device...
i can attest to that. all of my cheap power banks demonstrate this behaviour.
more importantly, as the article suggests, it can be hard to know if the battery itself is powering the device while plugged in (while getting charged) or if there is a passthrough, a la laptop charger.
Then you have a string of devices that need to be connected together in a more n rigid fashion, either in separate compartments of a bag or case with a USB cable between, or strapped together with tape.
"PiJuice will use up to just five of your GPIO pins (just power and I2C), the rest are free to diversify your project. The stacking header allows you to continue to use your existing HATs and add-ons with PiJuice." from https://uk.pi-supply.com/products/pijuice-standard
But sure, some people/projects might prefer to shift the hardware to not be attached to the Pi. I wouldn't be surprised if you could find a product that does that too, or at worst I presume a basic plastic box (there's probably pre-made ones for the size of various Pi HATs? and of course 3D printing) and some fairly simple DYI wiring to connect the 5 pins through a cable wouldn't be too tricky.
I used one of these for about a year on my PiHole, but switched to a standard UPS because the hat's LiPo started bulging from all the heat generated by the Pi's processor.
The hat is a great idea in principle, but because the battery is sitting right on top of the processor, it doesn't stand a chance given that lithium batteries are fairly temperature sensitive.
Hit Amazon.com and search for "raspberry pi UPS" and you'll find plenty of options. Or more generically try search terms like "mini ups" or "router ups" or "dc ups" - loads of options at places like Aliexpress as well.
Here in South Africa with rolling blackouts happening fairly regularly these days a lot of homes have something similar to keep internet connectivity live when it happens, with a lot of those options having USB outputs as well.
Mine came from https://www.geewiz.co.za/ups/124927-acconet-poe-48v-24v-smar... Looks like this may be a South African domestic brand though (and you probably don't want to order from a South African site unless you're living in the country to be honest).
One thing to be wary about though is max power if you're trying to run a raspberry pi with hard drive attached off one of these devices. A lot of these devices cap output on the USB ports at ~5V/2A (which I think was the USB2 max whereas USB3 allows for more). If you're running off an SD-card or SSD you should be fine, but 2A isn't enough to start a pi from an attached 2.5" HDD in my experience.
Not usb but mini UPS to keep your modem going is a common thing in India nowadays given constant power interruptions.
Ironically I got mine before I learned of the power cuts in my new home while building it. I was just merely thinking of edge cases of how a smart thief could undo my security cameras and figured cutting off the power would be one option I need to prepare, so got this UPS to backup both the modems (and redundant internet connections) and the home bridge for the battery backup security cam.
Not quite that but I ordered an Eaton 3S 850, which is a beefy power strip with built-in battery and looks like a decent compromise for cases where you don't really need a huge noisy rack-mounted UPS, but something that can do a bit more than just a Raspberry Pi (i.e. several Pis plus the router).
But would you only need 5V? DSLAMs here have an hour or so of UPS capacity as well, so if the router stays up, so does the internet connection, same with 4G/5G routers. Though I guess a 5/12/24V DC mini-UPS would still be a lot easier than actual 110/220V AC.
For some non-UPS but related use cases... I don't think it's uninterrupted, but I use this Anker PowerCore Fusion III as my main wallwart USB-C fast-charger, with the bonus that it also keeps its own internal 5 Ah battery charged: https://www.amazon.com/gp/product/B085CFD3Z9/ Current model might be: https://www.amazon.com/dp/B01K702S66/
If you have corruption or super long reboots on brief power loss, you have a bigger and unnecessary problem, because UPS can also fail and for many applications a brief service loss is otherwise acceptable. For example, I often handle California power outages by running an inverter off my car and powering up my home network through a cord run through kitchen window. If my NAS got borked in between, that would be very unfortunate. Your point stands in regards to equipment like security cameras where continuous availability is the point. But would a Raspberry Pi usually be the best choice vs special design equipment with built in backup batteries and low idle drain or say a cheap Android phone running an appropriate app?
I have made a standard USB-PD powerbank into an ACTUAL UPS by connecting a small board that allows you to manually select the voltage of the output. By selecting 12V you can then wire up any 12V device of reasonable power (say a wireless router) to the USB powerbank. There is no loss converting to and from AC and the power bank internals still handle all the complicated charging and whatnot. All the little IO board does is request a specific voltage (in the same way that any device with PD will negotiate) and keep it there.
I also found a small fanless inverter that I wired to this setup which gave me a tiny and completely silent AC power device. Super small, super portable. Easily powers a few LED bulbs or strings.
> Herein lies the problem – just because you have pass-through charging does not mean that your output is uninterrupted.
Okay, so this Framework laptop I'm typing on can power from any of its 4 USB-C ports. Ignoring that it already has a battery (you can buy just the motherboard and a non-laptop case), doesn't that work around this neatly?
Plug one USB-C directly to wall, plug second USB-C to powerbank.
For absurdity, repeat until you have a highly available array of 3 powerbanks. You can even put them on timers so you don't need pass-through charging!
Living in Mexico City around a lot of construction, I've had my heart (and kit) broken by dirty, inconstant power. For small things like a Wifi repeater a 10Ah battery inline works ok. But for anything beefier or without its own internal battery, eg a NAS / printer / modem, you still need a proper UPS.
The end result is we have a 750-100VA box under every desk and one in the comms closet. Unsurprisingly even small office supply stores around here have a wide selection of UPS and power kit.
My ZMI PowerPack 20k & 20k Pro's are still my daily drivers (good for 45W/65W only, but fine for my use), but I did snag one of these off the indiegogo (for the high-speed dual port capability). I hadn't realized it has this uninterrupted capability- awesome. I use USB-C to dc-barrel jack adapters, and this it an makes an affordable, reasonable capacity UPS.
Aside from what one thinks personally of him, it's worth noting esr's attempt to start an open source ups project (upside): https://gitlab.com/esr/upside
This is something one of my side projects aims to fix. Basically make a programmable battery source out of 18650 cells, USB Type-C, with automated charge & discharge control to keep it between 30-80% for UPS or Solar augmented use cases
About 10 years ago I tried using an Anker power bank for a UPS. It had some issues w/shutting itself down when switching power modes. I reached out to their support line and they completely misunderstood my questions, sending me a brand new battery instead despite my protest. I was hoping to just send some feedback on what I thought were firmware issues.
In the end I got two beefy Anker power banks that didn't work as a UPS, and eventually migrated myself over to using PoE power for the Pis (AliExpress gigabit -> 5V/3A PoE extractor), with a Unifi Dream Machine Pro SE powering them.
My UPS is now a used, enterprise Dell 1300W monster that pretty much runs the entire local networking stack + servers for nearly an hour without power.
Knowing very very little about battery technology I wouldn't expect an interruption when starting to charge a pass-through power bank either. I'd expect charge controllers to handle this seamlessly, like the ones I get on those microcontrollers that support batteries out of the box (which are dirt cheap too), or the one in my laptop, or the one in pretty much all other battery-powered devices; those don't switch off when connecting/disconnecting to/from mains power. If that's so well-understood, why would a decent power bank not do this as well?
Actually, my big Anker 521 (256Wh) does provide pretty much uninterrupted power when connecting/disconnecting to/from mains, though it did switch off randomly once after a few days.
There's no reason anymore that a power bank should ever even have an off mode unless it's so cheap there's no passthrough, which shouldn't be a thing either because it's annoying and probably saves 50 cents.
It's microamps with a good eco mode switcher.
Inline USB ultracapacitor banks seem like a reasonable product too though.
Hopefully USB will give us standards for power banks someday so you can get certified ones with a defined form factor and behavior.