Really stupid idea, what if there was a way to plug a 9V battery into your laptop as an expansion card or through Usb-c to charge your laptop. is this even possible? I know laptops take 9V, but would it work?
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Mate, this is such a crazy idea! Not stupid at all! The 9 volt battery would provide a tiny amount of charge, probably not enough to be useful. Any EEs here feel free to slap me for considering this 
but if you have a stack of 9Vs like say a 1000 in parallel then surely they could charge the laptop a tiny bit? a quick search showed that 9Vs have a capacity of 500mAh, so 1000 of them would be 500Ah. That equates to 4.5KWh compared to the Framework Laptop 16 Battery - 85Wh! It would be an expensive exercise unless you get the batteries in bulk on a superspecial deal!
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Sure, you’d just need a relatively low power pd powerbank chip that is fine accepting 9v (theoretically ou’d only need a mosfet and some pd comms to tell the pd controller you got 9v and a current limit but powerbank chips are much easier to get and work with and at low current the conversion losses aren’t a big issue).
The problem is as far as disposable batteries goes the 9vs have kind of horrible energy density as they are multiple cells stuck into a casing (usually 6 AAAAs in a trenchcoat these days) so you would probably be better off using a bunch of AAs. They also usually only deliver their full capacity when discharged pretty slowly which doesn’t really lend itself to this application where you’d likely drain multiple per hour (good alkaline apparently top out a bit under 5Wh, disposable lithium can go over 10 but boy are they expensive).
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The internal resistance of a 9V battery is too high that 10mA is too large. It’s probably won’t be able to power a laptop for a second
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That highly depends on the battery, but you can pull hundreds of ma from most 9v batteries but you won’t be able to extract anywhere near the full capacity at those currents. Also for alkalines the internal resistance rises signifficantly as they discharge.
If you can find a nicd 9v you don’t have to worry about internal resistance but it’ll have so little capacity it doesn’t matter anyway XD.
Yeah no way it would be able to power it on it’s own but I could probably trickle in a couple W for a bit.
This 9V battery might work 
:
130Ah
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Jesus christ >1KWh disposable battery
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