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Must fight temptation to buy an overpriced raspberry pi (sopuli.xyz)
submitted 1 year ago by to c/linux@programming.dev
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original post: https://mk.moth.zone/notes/a8zer7ypj6uv02ka

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[–] 9 points 1 year ago (4 children)

That depends on the age and quality of the laptop. It's been a while since some started directly running off the cable when the battery is full.

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  • [–] 5 points 1 year ago (3 children)

    Huh? If it can be used while it is charging - which is all laptops since forever - then it will run off the adapter while plugged in. Regardless of the battery state. You cannot charge a battery and discharge it at the same time - if it is charging then power must be coming from anything other then the battery. Epically with LiPo batteries which you cannot continue charging after they are full - doing so will cause them to burst into flames. So all LiPo charging circuits will cut off power to the cells once they reach a desired voltage - weather that is considered 100% (aka once it reaches 4.2V) or at a configurable lower amount.

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  • [–] 2 points 1 year ago (2 children)

    Their comment was indicating that laptop batteries will be damaged if left plugged in constantly. Which is a thing that can happen with some laptops, and most old ones.

    My comment was about how some modern laptops when left plugged in, will charge the battery and then start running directly from the wall-power once the battery is full. They bypass the charging once it is indicated to have a "full charge".

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  • [–] 0 points 1 year ago (1 child)

    will charge the battery and then start running directly from the wall-power once the battery is full. They bypass the charging once it is indicated to have a “full charge”.

    That does not make sense. Batteries cannot be charged and discharged at the same time - they are either charging or discharging or neither. When a device is in use while it is plugged in the device is being run directly from wall power - and anything left if sent to charge the battery. The only devices that don't do that is ones that power off while the charger is plugged in - which does not include any laptop that I have ever seen, generally just smaller devices.

    Modern laptops have smarter controllers that can turn off charging before the battery is full or when other conditions are met. But none are able to draw power from the battery while the battery is being charged - that just does not make any sense.

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  • [–] 1 point 1 year ago

    Laptops run on "burst" computing profiles in a lot of engineering situations, occasionally this applies to both the thermal design (runaway heatsoak if used at full tilt) but also battery design. I've seen several machines that will dip into their battery in addition to the charger to boost performance and dump wattage into the chips beyond what would be available from the adapter alone. I don't necessarily think it's good design, but modern battery chems don't really give a shit about up/down momentary charge cycles. Also the Chem they're using is not LiPo based as that chemistry while allowing for significant amperage to be drawn, is not stable enough for a laptop that is generally expected not to ignite.

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