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I have a phone attached to my laptop using an USB so that it shares the internet connection over the wire without using Wi-Fi hotspot (it draws a lot of power). But it draws a lot of power from the laptop battery by an undesired charging.

I'd like to find out a way to let the kernel tell the USB chip to restrict the amperage towards the connected device so that the phone doesn't draw any power at all, but solely communicate the internet connection.

I've read the docs about USB power management, but unfortunately found nothing I can use.

Is it even possible? If not, than what is the catch?

marked as duplicate by sourcejedi, Thomas, Kiwy, Rui F Ribeiro, schily Jul 2 '18 at 12:29

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  • 1
    Do you mean current? – ctrl-alt-delor Jul 2 '18 at 11:28
  • Why do you think that this is bad for the phones battery? – ctrl-alt-delor Jul 2 '18 at 11:30
  • You should be able to configure it to tell the device (phone), not to take much current. However see my answer, for why this may be bad. However limiting charge rate, may extend battery life. – ctrl-alt-delor Jul 2 '18 at 11:38
  • I'm voting to close this question as off-topic because this is a hw question. – Rui F Ribeiro Jul 2 '18 at 12:15
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    I've updated the battery endurance part. I didn't mean anything with the battery health. Simply that having Wi-Fi hotspot turned on on phone results in earlier need for charge (by draining more power). – jirislav Jul 2 '18 at 12:18

There are a lot of myths about batteries going around.

If you are using NiCad, then fully discharge before re-charging. Failure to do so will reduce capacity, and is irreparable.

If you are using NiMH, this this is like NiCad, except that you can fix them. Just do a full discharge cycle every so often. 3 full cycles should get it back to 99%.

If you are using Lithium batteries (most modern phones and laptops). Then these don't care if you charge early. What affects there life is usage. The more you discharge and charge them the sooner they will die. Therefore the worse thing you can do is follow advice that is designed for NiCad/NiMH. The other thing that they don't like is heat.

  • it's not what I've asked for, but useful info, thanks – jirislav Jul 2 '18 at 12:22

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