USB-C Charging limit

Discussion in 'Dell XPS and Studio XPS' started by L521x2012, Sep 6, 2018.

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  1. L521x2012

    L521x2012 Notebook Enthusiast

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    Hi, I have an older 7.4mm charger (more than 100Watts). Dell sells a 7.4mm barrel to USB-C adapter. I have read that USB C charging supports only up to 100Watts.

    Will the 120Watt charger damage the computer if I use it in the USB-C port with the adapter? Or does the computer controller automatically limit the charging current to below 100Watts?


    To anyone wondering why I want to do this, I already have a normal 130 Watt 4.5mm charger. I'd like to use that one for travel and just reuse this older 7.4mm charger at home on my desk.

    Another dell 130Watt charger is $85 or so.
     
  2. _sem_

    _sem_ Notebook Deity

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    Not sure what this USB-C charging adapter does and what it is rated. USB-C PD must do power negotiation... Dell USB-C charging goes over the USB-C standard.

    There are also simple adapters to the 4.5mm plug, then the USB-C socket remains free.

    I think I've seen cheaper 130W Dell chargers.
     
  3. John Ratsey

    John Ratsey Moderately inquisitive Super Moderator

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    That's the sensible solution. Here's the adapter. I've got a couple. I've travelled with my Precision 5510 using a 90W PSU and one of these adapters. The computer will automatically adjust any battery charging to keep within the PSU rating after allowing for the other power demands.

    I presume that the Dell 7.4mm to USB-C adapter includes a bit of electronics to (i) interrogate the PSU to find out its rating and then (ii) communicate through the USB-C power delivery system to negotiate the maximum power. It's likely that the 19.5V PSU output is close enough to the USB-C standard 20V that the voltage doesn't need to be changed.

    John
     
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