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I forgot the power adapter for my HP notebook and needed to charge it. I tried it with the charger of my mobile phone which has a 5V 2.4A output.

Yet, my laptop does not load at all:

enter image description here

In English (translated with deepl.com):

The PC is not charging. Use the recommended charging cable and cord and ensure that it is plugged in directly.

In German:

USB

Der PC wird nicht aufgeladen. Verwenden Sie das empfohlene Ladekabel und -kabel, und achten darauf, dass es direkt eingesteckt ist.

And when I try to restart from hibernation mode or restart, the BIOS says that I need a 60W adapter but that the device is just 20W (which is wrong, but it is the guess of the BIOS).

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    It would seem unlikely the BIOS is reporting wrong wattage info since it gets that info through a data exchange with the power supply, and/or the USB-C firmware of the cable itself. Most, if not all, USB-C cables will have firmware that does a data exchange with the power supply to ensure the cable isn't subjected to unsafe voltage/amperage loads (you wouldn't want a 30W phone charge cable to try and supply 45W, 60W, or 100W of power since that would fry the cable's firmware chip and likely result in the cable catching fire from the heat produced from the resistance).
    – JW0914
    Commented Jul 1 at 9:55
  • @JW0914 Then this charger may have 20W=VA, but it can output only 5x2.4VA. I can check this in the next days by just plugging in the charger again and making a picture of it, perhaps I remember it wrong. Yet, this is also not the main thing of the question. I can just pass the warning and still start the laptop, and then it can load from the mobile phone's charger. It worked loading it by 14 % in half an hour. And it was at 100 % after the night. Which means that I can leave the heavy power adapter with its cable at home when I travel.
    – questionto42
    Commented Jul 1 at 10:01
  • USB cables aren't created equally, even if they look the same - a phone charging cable should never be used to try and supply power to a laptop unless it's 100% known that cable can support the voltage and amperage load of both the charger for the laptop and what the laptop expects. USB phone charge cables will normally support 20W or 30W, depending on the cable (Volts x Amps = Watts), with some doing 45W with a specific charger. High wattage laptop charger cables are required for charging laptops, smartphone charging cables can't be safely used
    – JW0914
    Commented Jul 1 at 10:14
  • (Cont'd...) Using the wrong cable can result in a real fire risk and simply isn't worth the risk - even using the wrong cable to charge a phone has resulted in multiple documented fires and deaths in China. Laptop charger cables must be able to safely pass enough voltage and current to both charge the battery and power the laptop - this is why they're larger/bulkier.
    – JW0914
    Commented Jul 1 at 10:17
  • @JW0914 If I load it while I work on it, the battery lasts for a very long time even at <10 percent, and if it catches fire, I can just become aware of that while I work on it. It obviously does not damage the notebook. Thus, if you have forgotten your power adapter, or if you want to save some weight in the rucksack over a day or two, this is at least better than nothing.
    – questionto42
    Commented Jul 1 at 13:39

1 Answer 1

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You need to have a faster charger with at least 5V 3.0A output to have the chance to load at all. It takes much longer then, but it works. If I plug it in at low energy, the battery is said to last 8 hours to even more than a day.

I thought I would have to take the power adapter of the laptop, that the laptop would find out by some means whether it is not a right charger. But it can just load from the mobile phone charger if it is not below the threshold which must therefore be higher than my 5V 2.4A charger and surely works at 5V 3.0A.

Mind the danger of fire

A remark says that this is risky business since the device can catch fire, which has happened quite a few times. But if you work on it or have it nearby while it charges so that you would become aware of an overheating, it should be less dangerous. Have a good cable, that goes without saying.

Do this only seldomly

This should be done seldomly, only if you cannot avoid it.

I often leave the power adapter at home to save some weight in the rucksack. At work, there are power adapters as well. By this, I do not need to take it with me if I commute. Yet, if I happen to stay away from any power adapter for more than a day, I can at least take the small charger for my mobile phone with a high output, that is better than having no energy at all.

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    "at least 3.0A " is likely a red herring. You need a charger that has both the voltage and minimum current your laptop requires. Chances are your laptop mentions 12/15/20V and your alternative 3A charger is capable of putting out one of those voltages while the 20W one is limited to 9V. In most cases you need a USB PD or PPS (Programmable Power Supply) charger for a laptop. superuser.com/questions/1532426/…
    – Mokubai ♦
    Commented Jun 30 at 19:07
  • @Mokubai This remark is now outdated since my question was not clear at the beginning. I changed it now and made clear that I do have a power adapter for the laptop, and this question is about loading the laptop with a mobile phone charger instead.
    – questionto42
    Commented Jul 1 at 13:40

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