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   mhoye (mhoye@mastodon.social)'s status on Sunday, 23-Feb-2025 05:14:08 JST mhoye

   Lazyweb: if I want to power a smallish USB-c pi-like device in a way that provides it with clean power and very modest but reliable battery backing, what is our preferred way of doing that?

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Sunday, 23-Feb-2025 05:14:08 JST Rich Felker

     in reply to

     @mhoye Does it need to be able to negotiate USB PD, or is just having 5V at 2.1A or whatever you get with the data lines tied sufficient?

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Sunday, 23-Feb-2025 05:25:06 JST Rich Felker

     in reply to

     @mhoye I have this on order from Ali https://www.aliexpress.us/item/3256804201390760.html which supposedly gives up to 20V and can be used with a wide range of input (battery) voltages. You'd have to supply the battery and charging side separately. You can check back in a week or so and see my findings on whether it's actually decent.

   • Embed this notice
     mhoye (mhoye@mastodon.social)'s status on Sunday, 23-Feb-2025 05:25:07 JST mhoye

     in reply to

     • Rich Felker

     @dalias I believe that I need negotiation up to 15v, target is a small risc device.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Sunday, 23-Feb-2025 05:35:06 JST Rich Felker

     in reply to

     @mhoye Anyway, to keep in mind in general: if you don't want to have 4S or more of batteries (4 18650s or other lithium cells in series), getting 15V output is going to need a boost converter somewhere. So you'll either need a fancy PD module like the above that configures the boost using PD, or you'll need a separate-stage boost to give >15V input to a buck-only PD module.

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     Rich Felker (dalias@hachyderm.io)'s status on Sunday, 23-Feb-2025 05:37:31 JST Rich Felker

     in reply to

     • Stewart Russell

     @scruss @mhoye No charging is actually the selling point to me. I don't trust anything that integrates the charger not to disrupt output re-negotiating PD when the charging input status changes. And that would reboot the device I want UPS on and break the whole point of "uninterruptible" backup power.

     The charging side can be handled by putting a cheap BMS on the battery.

   • Embed this notice
     Stewart Russell (scruss@xoxo.zone)'s status on Sunday, 23-Feb-2025 05:37:33 JST Stewart Russell

     in reply to

     • Rich Felker

     @dalias @mhoye no charging side on that is a bit of a downer

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     Howard Chu @ Symas (hyc@mastodon.social)'s status on Sunday, 23-Feb-2025 22:26:21 JST Howard Chu @ Symas

     in reply to

     @mhoye cheap mini UPS. I have a couple of these on AliExpress:
     US $12.56 | DC UPS 5V 9V 12V Output 6x 18650 Battery Uninterrupted Power Supply DIY Power Bank Box for House Router Cellphone Tablet Modem
     https://a.aliexpress.com/_EQdTrvA

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Sunday, 23-Feb-2025 22:26:21 JST Rich Felker

     in reply to

     • Howard Chu @ Symas

     @hyc @mhoye Output is only up to 12V (vs 15 needed, 20 desirable for wide compatibility) and that's a lot of batteries you have to supply.

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     Howard Chu @ Symas (hyc@mastodon.social)'s status on Monday, 24-Feb-2025 00:22:24 JST Howard Chu @ Symas

     in reply to

     • Rich Felker

     @dalias @mhoye there are other models available. I like these DIY boxes because I can choose the quality of cells I use instead of just getting whatever noname stuff in a fully packaged product. And I can replace them in a few years when they wear out.

     Rich Felker repeated this.
   • Embed this notice
     mhoye (mhoye@mastodon.social)'s status on Monday, 24-Feb-2025 00:22:24 JST mhoye

     in reply to

     • Howard Chu @ Symas
     • Rich Felker

     @hyc @dalias replaceable standard cells is a very nice thing to have. With clean power and replaceable cells you can keep stuff out of a dumpster for far longer than anyone realizes.

   • Embed this notice
     mhoye (mhoye@mastodon.social)'s status on Monday, 24-Feb-2025 11:07:51 JST mhoye

     in reply to

     • Rich Felker

     @dalias I should have mentioned this earlier, but I am interested in your findings.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Monday, 24-Feb-2025 11:07:51 JST Rich Felker

     in reply to

     @mhoye Package just cleared customs so hopefully I'll know something interesting in a few days. I figure I'll be able to say "it's shit" right away if it's shit, but evaluating it as good is probably gonna take a lot longer.

   • Embed this notice
     Rich Felker (dalias@hachyderm.io)'s status on Friday, 28-Feb-2025 02:14:50 JST Rich Felker

     in reply to

     @mhoye It seems good. I don't have a setup for testing output voltages at the moment but my laptop is running/charging off it off a bench supply. Below 9V in I'm tripping overcurrent on bench supply under cpu load, but idle/charge works at 5V in. Efficiency goes down a lot below 9V in. With sufficient current supply I was pulling over 50W under simulated load.

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     Rich Felker (dalias@hachyderm.io)'s status on Friday, 28-Feb-2025 02:18:43 JST Rich Felker

     in reply to

     @mhoye Thermals seem to be holding at under 45°C.