Raspberry Pi 4B - Small form factor UPS for safe shutdown and autoboot

Does anyone have a recommendation for an uninterruptible power supply (UPS) that meets the following requirements:

  1. Safely shut down a Raspberry Pi 4B following a mains power loss event (ideally with a configurable qualifying time) and transition to battery power.
  2. Automatically boot the Pi, following restoration of mains power.
  3. Can be a HAT or external, but must have a form factor smaller than say: 150 x 150 x 150 (mm)
  4. Optionally: something that won’t require the replacement/destructive-alteration of my Argon One case.

I’m pretty sure I could use an Eaton 5S to get all but the form factor requirement.

It seems like the DFRobot UPS HAT won’t meet the auto boot requirement.

Hey Matt,

You should be able to use the DFRobot hat for that application, there’s a forum thread regarding a similar issue below.

Core Electronics | Support


Thanks @Bryce , but if you double check my post, I’ve already linked to that forum and repeated (if you scroll up from your linked comment) that I don’t think requirement #2 is met by that solution.

Thanks @brian86770, but I come from more of a software background than a hardware/electronics background, so I’m having trouble following your suggestion.

Ideally I’m looking for a solution that is ideally as off-the-shelf as possible, but if I need to go bespoke, I’m more capable of writing software than mucking around with the electronics.

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Has anyone had experience with the PiJuice HAT and know if it will meet my requirements?

Hey Matt,

Sorry about the delay in getting back to you, you should be able to use the DFRobot hat in this case, it’s quite similar to the PiJuice in many respects. The issue with being able to reboot after mains power is restored should actually be included in that functionality (although, this will likely require some modification of the HAT in order to setup). As soon as power is cut (when the script is configured correctly), the UPS triggers a safe shutdown of your Pi to avoid corruption and similar issues, then when the power is restored, the Pi should start-up as normal, similarly to if it was plugged in to the socket directly via its USB port. If you have any further questions please let us know.

Core Electronics | Support

Hi @Bryce ,

No problem.

Just to clarify, what makes you think the auto-boot will work (after a controlled shutdown) in my situation, if the person in the other thread said that DFRobot product page forum post said it can’t be done?

Do you know if the DFRobot HAT will work with (or even fit in) my Argon One case (note: I’m fortunate to have an Argon One case that does have beta firmware to auto-boot)?

Also, do you have a recommendation for a suitable battery to be paired with the DFRobot HAT?

Hi @Matt127169,

Unfortunately, the hat doesn’t fit in an Argon One, I also tried setting it up and you can likely find a way to be able to modify it to send the power on signal when the power is restored, but the difficulty of doing that will likely be harder than just using a totally external UPS which sends the shutdown signal before cutting power. As for a suitable battery, anything greater than 1000mAh at 3.7V from our LiPo range will do the trick if you would still like to use the DFRobot hat. If there’s anything else that I can help you with please let me know.

(This or higher capacity works)

Core Electronics | Support

Thank you @Bryce, I appreciate your effort.

I’ll do some more digging and report back.


I’ve decided it will be most feasible to move the Pi out of the confined space and go for a generic UPS.

Unfortunately couldn’t find any suitable small form factor generic UPS.

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Hi Matt,

In terms of a generic UPS were you after something interfacing directly with mains power?

Core stocks this UPS plug adapter that might work: https://core-electronics.com.au/uninteruptible-power-supply-12v-dc-18w.html
Note: it does output 12 V, a step-down regulator should get that working with the Pi.

How does that one look?


Thanks @Liam.
I’m actually looking at the Eaton 5S 550VA, as it has the smarts to output when mains has dropped out.

Just to clarify, I only made my last post for the benefit of the community, not as a question of what generic UPS to get.


Hey Mat,

No worries, the Eaton looks good for that application from what I’ve seen, make sure to let us know how you go, we’ve had a few customers asking about UPS for Pi-based (and similar microcontroller) projects. If you’ve got any recommendations for products please let us know and we’ll see what we can do to get some in stock.

Core Electronics | Support

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Hi @Bryce,

I ended up going for the Eaton 5e (850VA), because I’m powering an NVR as well (as my Pi).

Had some regret soon after purchasing it, because I assumed Eaton provided Linux software for ARM64 architecture (i.e. the Pi), but realised that they don’t. Contacted them about it and they were quite unhelpful about it (essentially told me tough luck).

Did a bit of research myself and managed to get what I originally intended to do via Network UPS Tools (which fortunately supports my Eaton).
I would note that the NUT route is not for the Linux/software faint hearted, so if you prefer GUIs, than look elsewhere from Eaton.

These are the guides I used for my NUT setup:

Also, one other annoyance (with this Eaton) is that disabling the beeper in the UPS doesn’t seem to persist (i.e. it gets enabled when the UPS power cycles).

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Hi Matt,

Glad to hear you found a solution in the end, and thanks for sharing!