Convert device that uses a/c adaptor to battery power

I’ve got a device that has a power adaptor that outputs 5v 4.6a DC from standard 110/120V AC input. It’s this Photobiomodulation therapy device

I’d like to make it more portable so not tied to an AC outlet.

For the past year, I’ve been working towards 1 cord to rule them all now that Adafruit has their USB-C to Barrel connector cord with E-MARK chips, these work great for powering QRP Ham radio’s like the Xiegu G90 depending on which connector adaptors you use.

My goal was to use the same setup with this device, but it looks like USB-C PD only outputs 9V 5A at the low end of the spectrum, so need to find some other solution. Doesn’t appear to be a 5V option.

My goal is still to power using USB-C PD battery packs. Any suggestions for an intermediary to bring the voltage and current to the appropriate levels. Prefer something off the shelf ideally but not impartial to building something.

The battery packs I am using are the


Suggestions on how to make this work?

Have you tried meowing at it?

5v 4.6a is quite a lot of power. You should get a power bank that can supply at least 30w and output a higher voltage lower current. Then use that USB trigger cable to get higher voltage then use high power step down voltage module. From 15v to 5v 5a.

Your power bank should be able to handle it. You just need the dc to dc converter module

Both powerbanks I have can supply at least 100W so the power is not a problem per se. The QRP radios can draw 50-60W easily when the Antenna Tuner is running for example, the Bioflex only drawing 25W isn’t a problem. As to dc to dc converter after the E-MARK cable, hmm, I assume that will need to talk to the E-MARK chip so it doesn’t tell PD to stop sending power? Time to delve into the USB-C standard methinks.

Any suggested/recommneded dc to dc modules?

Something like that probably would work. What is a emark chip? Like a USB pd trigger board?
I think the adafruit one will tell charger to output whatever voltage and it doesn’t need to communicate with each other for them to work.

I believe the full 5A is only available at 20V, and with an e-marked cable. If you need 5V, the limit is 3A and e-marking won’t do you any good. If you want to stay in spec anyway.

So if you need 60W @ 5V output, you’ll need to get into the 20V@5A profile and then buck it back down to 5V. To do this with off-the-shelf modules, you’ll need a normal e-marked cable, then a USB-PD ‘trigger’ board (which supports requesting 5A) to enable the 20V output, then a buck converter module. There might be self contained modules that can do all that on Aliexpress or somewhere but at that power level and low voltage it seems a bit niche.

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5A is available with E-MARK chip at 9V, 12V, 15V and 20V, just no 5V option. Ahh PD Trigger board, right… in the Ham radio space, that’s what a lot of QRP operators were using before Adafruit et al came out with their e-marked cables, eg

Though they call it a PD Decoy board at link above.

@KittyCat - Pretty sure I saw something like that Ali Express item on Amazon just recently and wondered what the use case would be, now I know!

Ah you’re right, it looks like this is supported in the programmable power supply mode in ‘modern’ USB-PD, but not the fixed profiles offered in the earlier versions. I wonder if these cables are actually negotiating that way or if they just assume the source will let them pull 5A on a 3A profile.