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Comment by rcxdude | Hacker News Reader

The other issue with USB PD without a battery is that most chargers with multiple ports will drop the connection and renegotiate if any of the ports are plugged or unplugged (whether they need to in order to supply the new device or not).

(Relatedly, there's an empty niche in the market for a USB-C power bank that can act as a UPS: able to charge and discharge at the same time without interrupting the discharge port when the charge port is disconnected)

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> Relatedly, there's an empty niche in the market for a USB-C power bank that can act as a UPS: able to charge and discharge at the same time without interrupting the discharge port when the charge port is disconnected

I think there's a soft version of this already available. The term is "pass-through" charging. The power bank that I have [1] will charge itself and the devices at the same time (albeit at reduced rates suitable for overnight charging).

I agree that it would be super useful to have a device that is explicitly designed to provide maybe 5V/5A for a Raspberry Pi 5 without interruption, and perhaps double as a power bank.

[1] https://www.amazon.com/dp/B0DHRYDNXL

As far as I know, pass-through power banks will still universally drop the power on their output momentarily when they lose the connection on their input, though. That's the missing bit.

I confirm, baseus chargers really reset all ports when you change the number of consumers. But I think you usually have a choice between caring about a custom power source or using a standard one. IMHO, using a dedicated PD charge is still more convenient than alternatives.

they sell modules on AliExpress that claim to do that

https://a.aliexpress.com/_Ez4GjPQ

and some powerbanks advertise passthrough charging eg. https://amzn.eu/d/hApICf9

That one, sadly, does not have USB-C output, so it's fine for something you're wiring up custom but isn't a generic solution (which, to be fair, is the quite niche overlap of wanting to power something with USB-C without a battery and wanting battery backup).

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