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1. Embed this notice
   Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:29:17 JST Rich Felker

   Stupid "expert" advice: "Don't use USB-C PD-trigger to laptop barrel cables because your laptop might need over 100W! At best it might just charge slowly when your laptop is powered off."

   My bench supply's power readout running my laptop: "7.5-9.1W"

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:30:42 JST Rich Felker

     in reply to

     Actual worst case: the USB PD overcurrent trips when you do something power-intensive, so the laptop runs off battery for a few seconds while it's resetting, then it starts powering again, repeating until you're not overcurrent. 🤷

   • Embed this notice
     cliffle@hachyderm.io's status on Saturday, 01-Mar-2025 07:41:31 JST cliffle

     in reply to

     @dalias I charge laptops and things from limited DC supplies kind of a lot, and as far as I can tell, every one made in the last 20+ years carefully regulates how much power it draws from the charger. Your laptop might be _able to_ charge at 100W, but if the voltage starts drooping at 45W, it'll work that out.

     So, yeah, ignore this "expert," those PD-to-barrel cables are great.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:47:14 JST Rich Felker

     in reply to

     • cliffle

     @cliffle Well the USB supply is likely to trip overcurrent protection before the voltage drops enough for the consumer to notice and back off, unless the trigger circuit is aware of the negotiated current and has its own current limiting logic.

     But yeah this is almost surely a non-issue anyway as long as your device has an internal battery that lasts for more than 30 seconds.

   • Embed this notice
     cliffle@hachyderm.io's status on Saturday, 01-Mar-2025 07:48:25 JST cliffle

     in reply to

     @dalias it's true. TBH I feel like USB-PD is my favorite thing that's happened to DC supplies recently. I get folks' frustrations with USB-C more broadly, but this whole "power supply is smart and can negotiate while still being cheap" thing is neat.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:50:12 JST Rich Felker

     in reply to

     • cliffle

     @cliffle Yes and no. I kinda also hate it - the whole reason I got into messing with this stuff is because I have an ISP-provided modem that I can't just DC-UPS with a 12V battery and buck/boost because it refuses to accept power except from a 20V capable USB-PD source.

   • Embed this notice
     cliffle@hachyderm.io's status on Saturday, 01-Mar-2025 07:53:25 JST cliffle

     in reply to

     @dalias ugh, yes, that does sound annoying. One of the projects in my backlog is a little board that takes DC and negotiates PD source at the voltage you tell it to, because I can't find one on the internet.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:54:22 JST Rich Felker

     in reply to

     • cliffle

     @cliffle I got one for $7 off Ali. https://www.aliexpress.com/item/3256804201390760.html

   • Embed this notice
     cliffle@hachyderm.io's status on Saturday, 01-Mar-2025 07:55:32 JST cliffle

     in reply to

     @dalias Well, that saves me some time! Thanks!

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 07:56:44 JST Rich Felker

     in reply to

     • cliffle

     @cliffle The ICs it's using seem to be the right way to do this. AIUI SW2303 is full coverage PD/QC negotiation and PL5501 is integrated buck-boost.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Saturday, 01-Mar-2025 08:03:12 JST Rich Felker

     in reply to

     • cliffle

     @cliffle Great! I've got it powering my laptop right now to evaluate it, but once I get batteries setup I'm going to put it on the router.