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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 yo

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.

jacknews 4y ago
Sure but you'd need bigger pockets, probably even a bigger backpack.
- dicknuckle 4y 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
  - axiolite 4y ago
    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.
rwmj 4y ago
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 ...
- fy20 4y ago
  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.
  - axiolite 4y ago
    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.
crashingintoyou 4y ago
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.
greggsy 4y ago
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.
- unregistereddev 4y ago
  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.
  - deleted 4y ago
    [deleted]
- tenebrisalietum 4y ago
  I heard of connecting an old modem to a serial port for this purpose. If it doesn't respond to any AT commands then power may be out.
  - Nextgrid 4y ago
    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).
- justsomehnguy 4y ago
  And couple of months later you are investigating why the branch gone dark in the middle of the day. No. Devices should survive powerloss, devices can have a graceful shutdown from an external source. Key is in your "might".

jacknews 4y ago

Sure but you'd need bigger pockets, probably even a bigger backpack.

dicknuckle 4y 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
- axiolite 4y ago
  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.

rwmj 4y ago

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 ...

fy20 4y ago
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.
- axiolite 4y ago
  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.

crashingintoyou 4y ago

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.

greggsy 4y ago

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.

unregistereddev 4y ago
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.
- deleted 4y ago
  [deleted]
tenebrisalietum 4y ago
I heard of connecting an old modem to a serial port for this purpose. If it doesn't respond to any AT commands then power may be out.
- Nextgrid 4y ago
  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).
justsomehnguy 4y ago
And couple of months later you are investigating why the branch gone dark in the middle of the day. No. Devices should survive powerloss, devices can have a graceful shutdown from an external source. Key is in your "might".