Can i charge one laptop from another laptop using the type c power delivery port on both

Discussion in 'Overclocking & Hardware' started by n2p4u, Mar 23, 2020.

  1. n2p4u

    n2p4u Member

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    Can i charge one laptop from another laptop using the type c power delivery port on both
     
  2. CAPT-Irrelevant

    CAPT-Irrelevant Member

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    Heck no. The port won't be able to sustain the amps output required. That'd be like using a 500mAh charger on a 2Ah device. Laptops require their own or close equivalent ampage charger for a reason.
     
  3. spit051261

    spit051261 Member

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    Nooooo
    Separate charger dude .
     
  4. OP
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    n2p4u

    n2p4u Member

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    it doesnt look it can ut my 5 volt 2A charger is charging it?
     
  5. CAPT-Irrelevant

    CAPT-Irrelevant Member

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    ... I think you've answered your own question.

    Otherwise, explain what you mean?
     
  6. Ratzz

    Ratzz Member

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    Just throwing a spitball here, not actually knowing the answer.. but if the output of the donor USB port is 500mAh, and the receiving machine has a lower battery charge than the donor machine, would it not attempt a power balance between the two devices?

    As in, the laptop with the higher battery level would attempt to charge the machine with the lower battery level until they reach equilibrium? Thus, the answer would probably be yes, but the RATE of charge would be limited to the output ability of the donor port, ie 500mAh, so yes, but really slowly, and only as long as it takes for both machines to have similar charge levels?

    Obviously if the donor machine is plugged into the wall via a much higher output charger, then eventually both machines would be fully charged - provided of course the donor machine is not using all of the available input power and the machine being charged using significantly less than the 500mAh available to it.. as in, being turned off for instance?
     
    Last edited: Mar 24, 2020
  7. CAPT-Irrelevant

    CAPT-Irrelevant Member

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    OP, at this point, we're going to need to know the model numbers of the laptops you have.
     
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  8. terrastrife

    terrastrife Member

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    Check laptop specs to see if it supports charging of other devices. Most modern HP's I know can do up to 15w output.
     
  9. OCMunkee

    OCMunkee Member

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    Ok so the replies here are annoying me too much to not reply.

    Amperes (shortened to amps or A) is a measure of CURRENT. i.e. the amount flowing at a point in time
    Amp Hours (Ah) or milliamp hours (mAh) is a measure of CHARGE i.e. the amount of energy stored or used over a period of time
    Watts (W) is a measure of POWER i.e. the amount of energy in use or being used at a point in time

    TL;DR You might be able to, but both devices need to have compatible USB-PD input/output options.

    Now, if you want to know whether you can charge one device from any other device, you have to think of how the spec works.
    USB Power Delivery (USB-PD) is defined by the USB Implementers Forum (USB-IF): https://www.usb.org/usb-charger-pd

    Note that USB-PD is NOT the same as Qualcomm's standard, and there are a few different revisions, so it depends on what both your devices will support.

    USB-PD allows a device to act as either a source (i.e. providing power) or a sink (i.e. receiving power), it may be able to perform both roles, sometimes even both simultaneously (though presumably not from the same USB socket). For your device to be charged by another, they need to negotiate this connection. This requires the source device to support providing power output in the same configuration as a supported input of the sink device.

    Typically supported configurations may include:
    Voltage: 5-20 volts DC. Usually 5V, 9V, 12V, 15V or 20 V)
    Current: 0.1-5.0 amps. Usually 0.5-3.0A at 5V, 1.0-3.0A at 9V or 12V and 1.5-5.0A at 20V.

    Consider the below example:
    Laptop (LAPPY) and a mobile phone (MOBIE) using USB-PD over a USB-C to USB-C cable, and lets assume you have a quality cable that meets the spec.

    MOBIE supports the following USB-PD configurations:
    Sink: 5V @ 0.1-3.0A, 9V @ 0.5-2.0A
    Source: 5V @ 0.1-1.0A

    LAPPY supports the following USB-PD configurations:
    Sink: 9V @ 1.67-3.0A, 15V @ 1.0-3.0A, 20V @ 2.0-3.0A
    Source
    : 5V @ 0.1-2.0A, 9V @ 0.5-2.0A, 12V @ 0.5-2.0A

    If you look at the overlap there, you're probably definitely not going to be negotiating the mobile phone to act as a source for the laptop, but it's almost certain to work in the other direction.

    So, lets introduce another device, a battery pack that has some additional options.
    BOZO is a big bastard of a power bank, it uses USB-C with Power Delivery to charge itself, as well as to provide output.

    BOZO supports the following USB-PD configurations:
    Sink: 5V @ 0.5-3.0A, 9V @ 1.0-3.0A, 15V @ 1.0-3.0A
    Source: 5V @ 0.1-3.0A, 9V @ 0.5-3.0A, 15V @ 0.5-3.0A, 20V @ 1.5-2.25A

    Well, now you are able to charge in EITHER direction, as BOZO can both provide USB-PD Source at a compatible range for LAPPY, but LAPPY can also provide a source to BOZO.

    So how do we know which will work?
    Usually, there will be some sort of manual trigger, or it will depend on the firmware on either device and how they negotiate their USB-PD connections. Sometimes a powerbank might have an INPUT-only PD port, and OUTPUT-only PD port, but some of them only have a single port, so you have to somehow get it to recognise when to charge itself and when to charge the connected device.

    I'll leave that up to others to try out, but as far as I'm aware that it's definitely possible based on the spec, but highly dependent on firmware and manufacturer definitions.

    ::EDIT:: Also, it is possible for a device to accept power input from something that will provide less power than it's currently using, so you CAN be plugged in and still draining battery if in heavy use.

    I've had this happen with my laptop connected to a charger was only capable of 30W (15V @ 2.0A) but my laptop was using closer to 40W, so even though it was plugged in and accepting power, the battery was still draining. It just drained slower than if I weren't connected at all. If I reduced the power use, e.g. idle, sleep, hibernate or off, I'd be able to charge the battery.

    ::EDIT AGAIN::
    I should also mention, having USB-C does not mean you have USB power delivery, USB-C is a connector form-factor, this connector may provide USB 2.0, USB 3.0 / 3.1r1, USB 3.1r2, Thunderbolt, displayport, or whatever else someone concocts to provide over that connector.

    Good ol' wikipedia has some helpful info https://en.wikipedia.org/wiki/USB_hardware#PD
     
    Last edited: Mar 24, 2020
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  10. OP
    OP
    n2p4u

    n2p4u Member

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    Okay, I was in a Rush and wasn't clear, two laptops both charge via USB C power delivery and only one USB C to C power delivery cable. I have charger for laptop a which takes charge from either charger or type C of port, can I plug laptop a to it's non USB charger and have it's power delivery port output the power to laptop b. Essentially I'm asking is power delivery port bidirectional.
     
  11. connico

    connico Member

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    No it doesn't work that way
     
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  12. CAPT-Irrelevant

    CAPT-Irrelevant Member

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    OP is trying to supply charge to a laptop from another laptop. There's no phone/tablet/device involved in this context.
     
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  13. terrastrife

    terrastrife Member

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    The whole point of USB PD is that it IS bidirectional. But what the capacities are you will have to check specs. For Example HP laptops can output 15W (5v3a)
     
  14. connico

    connico Member

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    Lol bidirectional for lower amp/voltage devices. Not to power/charge a whole another laptop.

    He needs a USBC mains charger to charge is USBC only laptop or a high output battery capable of the charge input of the said laptop....

    15w isn't powering any laptop I know... It may charge the battery when the laptop is turned off but very very very slowly... But cannot confirm as I've never tried
     
    Last edited: Mar 24, 2020
  15. OP
    OP
    n2p4u

    n2p4u Member

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    My 5v 2a power bank was able to charge the lenovo laptop very slowly (while off)
     
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  16. terrastrife

    terrastrife Member

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    It's part of USB PD 2.0/3.0 so as long as the device conforms to either of these standards it will accept power. Sure if the device is using more than 15W then the battery level will still go down, but it still is charging.
     
  17. OCMunkee

    OCMunkee Member

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    The entire point of my post was to say that it's irrelevant what the devices are.
    It's purely about what spec it conforms to, and which common source/sink options are available.
     
  18. Cheep_Thrillz

    Cheep_Thrillz Member

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  19. CAPT-Irrelevant

    CAPT-Irrelevant Member

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    What model Lenovo do you have?
    And what's the make and model of the other laptop?
     
  20. OP
    OP
    n2p4u

    n2p4u Member

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    E495 AMD Ryzen 3500U
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