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It is discussed here that you could charge one laptop off another. Okay, cool. But what if they are both plugged in, then you attach them over USB? Do they both
by hellofunk 10y ago
It is discussed here that you could charge one laptop off another. Okay, cool. But what if they are both plugged in, then you attach them over USB? Do they both send a charge out, possibly cause one or both to fry? And what if you have multiple sources of charging plugged into the machine?
- prodmerc 10y agoI assume there's some form of auto negotiation? For what it's worth, I connected two laptops via USB, Nothing happened (though most likely they had built-in protection against that kind of bullshit)
- tajen 10y agoIn the case you plug two Macbooks together and to the powerpoint, it charges the electricity back on the grid, which paves the way to infinite energy. More seriously the macbook can choose one source for its power.
- moolcool 10y agoI would imagine there's both software and hardware limits to how much current the charging circuit can accept, since having multiple chargers to one device is pretty likely with USB C. Like imagine hooking up two USB C displays which both act like chargers.
- ageitgey 10y agoGood questions! It's all in the USB Power Delivery [1] spec. The devices will do reasonable things. For example if you plug four power sources into the MacBook Pro (one in each port), it will take power only from the source that is supplying the highest power. Or if you plug a cell phone into a USB-C hub, it will suck as much power as it can to charge it's battery as quickly as possible. But if the hub needs more power temporarily to spin up a hard drive, the charging device can momentarily reduce it's power draw and then resume charging when the extra power is available again. [1] http://www.usb.org/developers/powerdelivery/ http://www.usb.org/developers/powerdelivery/