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Can I use legacy chargers with usb-C charging thinkpads?

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likengmx
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Can I use legacy chargers with usb-C charging thinkpads?

#1 Post by likengmx » Wed Jul 05, 2023 8:50 am

I have a new X390 Yoga with USB-C charger.

I have old chargers from my other thinkpads. All 20V, with square connector and round connector (used for X230). And I have bought chinese adapters "square to USB-C" and "round to USB-C" in order to reuse my legacy chargers with the new laptop.I have tried them and they work, charging the x390.

However, later I read that the chargers must be PD protocol compatible, able to negotiate different voltages, and now I'm not sure if I can fry the X390.

Is it safe to use the old chargers?

likengmx
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#2 Post by likengmx » Thu Jul 13, 2023 6:28 am

Nobody knows? Is it perhaps a question for another subforum?

axur-delmeria
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#3 Post by axur-delmeria » Thu Jul 13, 2023 1:04 pm

IMO the old chargers by themselves are safe, what you should worry about is the quality/reliability of the USB-C converters that you bought, especially if you use them to charge devices that require voltages lower than 20v. The USB-C PD protocol allows the charger and device to negotiate the charging voltage (IIRC it's 5v, 9v, 12v, and 20v), but a shoddily-built converter might fail in a way that 20v is sent to the device regardless of the negotiated voltage. :x
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likengmx
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#4 Post by likengmx » Sat Jul 15, 2023 3:01 pm

I think they are passive adapters. Simple rewiring from old chargers to USB-C. So there are no comms. Always 20V.

My doubt is if a thinkpad x390 or x1 or x13 yoga can demand at some point while charging to lower the voltage, burning something.

axur-delmeria
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#5 Post by axur-delmeria » Sat Jul 15, 2023 9:37 pm

I doubt that they're passive adapters, because you need active electronics to make a proper USB-C device talk to a charger before any charging can take place.

That said, I doubt that the Thinkpad itself would ask for a voltage lower than 20v.
Planned Purchase: T480s i5-8350 FHD Touch
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likengmx
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#6 Post by likengmx » Sun Jul 16, 2023 10:34 am

I think you are right. I didn't see item's description:

Type: DC Converter Plug, PD E-Mark Chip,

Image

E-Mark Chip:

Image

So, I understand these adapters are safe, at least with 20V thinkpads. I don't know what would happend if you connect them to a 5V mobile with a 20v thinkpad power supply.

zoltan87
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Re: Can I use legacy chargers with usb-C charging thinkpads?

#7 Post by zoltan87 » Tue Sep 19, 2023 8:38 am

Very interesting, I have been wondering whether these active adapters existed. I have a bunch of Thinkpad power supplies laying around, both the 20v barrel plug variety, and also the older one from pre-T60 era with lower voltage (maybe 16v, I can't remember).

What I have been wondering is whether I could convert those psu units to work with my mother's Surface laptop 4. Anyone has any idea/opinion on the matter?
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