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I have bought cordless rotary tool. The charger which is included in the package is equipped with USB-C connetor, and the charger has rated output at 13V @ 1.5A.

Is this "legal" according to USB specification? This does not seem to be a smart charge so I think it cannot vary it's output according to the downstream device preference.

Am I correct that this charger would damage an USB-C device (tablet, phone, earphones, ...) which would be expecting 5V and only then negotiate higher voltage according to USB-C PD standard?

excerpt from tool manual showing the charder specs

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  • \$\begingroup\$ IIRC, USB Type-C /w Power Delivery (USB PD) allows max 20VDC. Am I correct that this charger would damage an USB-C device (tablet, phone, earphones, ...) which would be expecting 5V and only then negotiate higher voltage according to USB-C PD standard? If this charger has a constant-voltage (CV) output configuration, which is not able to adjust its output voltage for specific devices/situations then yes, it would. \$\endgroup\$ Aug 6, 2020 at 8:30
  • \$\begingroup\$ Check if they advertise it as USB anywhere on the packaging. Also if they show USB logo. It would be illegal to show the logo or advertise as USB compatible. It may not be illegal to use the USB connector and NOT mention anything about USB. Your screen shot doesn't have any mention of USB or its logo. If it was USB compatible they would have added the logo. The absence of the logo is conspicuous. \$\endgroup\$
    – AJN
    Aug 6, 2020 at 10:42
  • \$\begingroup\$ USB logo guidelines SE question about power ONLY cable another SE answer \$\endgroup\$
    – AJN
    Aug 6, 2020 at 10:56
  • \$\begingroup\$ Can you post a photo of the connector ? How sure are you that it is USB-C type ? \$\endgroup\$
    – AJN
    Aug 6, 2020 at 10:57

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13V is a very unusual voltage for a USB charger. The only way to achieve it within the USB standard is to implement USB Power Delivery 3.0 plus PPS (Programmable Power Supply), which allows to change the voltage in small increment. Even then, the maximum voltage would either be 12V or 20V.

This charger could still be safe if:

  • It initially delivers 5V only.
  • Detects that it is connected to this specific tool and then increases the voltage.

However, I've seen web pages stating that it constantly delivers 13.2V. With a multimeter, you should be able to verify this claim.

If it is true, then this charger is very dangerous for all USB hosts and devices with a USB-C port. Watch out.

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    \$\begingroup\$ With USB-PD "trigger boards" available for hobby projects at $10 it should not have been terribly difficult or expensive to put USB-PD PPS into the tool. A trigger board is a small PCB with an IC, USB-C connector, and a few other bits, to add USB-PD function to home brew devices. Incorporating this into the design of the tool could possibly added only pennies to the cost since there's already a USB-C connector, PCB, and so on in the tool. A USB-C PPS charger would be an off the shelf device and likely cost no more than a bespoke 13 V charger with a USB-C connection. \$\endgroup\$
    – MacGuffin
    Jun 16, 2021 at 0:18

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