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Comment by dns_snek | Hacker News Reader

Is there a good reason why we can't tell our devices to charge the battery to say 70% and then internally disconnect the battery, so it's neither charging nor discharging?

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Some laptop manufacturers include this mode. At least I have it in lenovos (not exatctly 70%, they allow cap at 80%), and have seen in some samsungs years ago.

Where do you set this? OS, BIOS or some Lenovo control software?

On Linux you can set this in /sys/class/power_supply/BAT?/charge_{stop,start}_threshold – you can read and write a percentage (1-100) to there. You'll have to set it on every boot.

I assume there's some way to do this in Windows as well, but I don't know it.

At least one of those; depends on the device. As sibling comments note, plenty of devices expose it in software, where in Windows you use the vendor's utility and Linux puts it in /sys, but I've got laptops that either don't do that or I couldn't find it but I could configure it in the BIOS settings. So you might have to dig around a little.

Lenovo vantage, under battery management or something like that. Has been an option for quite long.

ThinkPad has this. My battery only charges to 75% and it must drop to 50% before it starts charging again. You can configure any value for either setting with TLP.

On my thinkpad the screen dims after 30seconds without keyboard activity when not fully charged. Very annoying. It happens also when connected to a charger.

I regretfully set the bios to fully charge again to disable this auto-dim feature.

Is the screen dimming not a setting in your OS?

Dell laptops have had such a feature literally for a decade now

Yep. I'm using Linux on a XPS 13 and Dell provides Dell Command Configure, aka, cctk. I set mine to 65%.

https://www.dell.com/support/kbdoc/en-us/000178000/dell-comm...

That's good to know, I guess I'm curious why it's not (nearly) ubiquitous. Does it add significant cost and complexity to hardware design?

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