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I will do this now with my new macbook pro and an old thinkpad. I will update you with what happened. Lenovo at 50% charges Macbook at 100% if and only if the

I will do this now with my new macbook pro and an old thinkpad. I will update you with what happened. Lenovo at 50% charges Macbook at 100% if and only if the right macbook port is used. If another macbook port is used, nothing happens. When using this one macbook port (the one right next to the charging port) lenovo also tried to set up a new "macbook pro device", I didn't let it finish. The Lenovo has just one USB-C port. I now wonder what two macbook pros or two lenovos would do to each other.

atemerev 4y ago
famous last words!
johnwalkr 4y ago
I have a work (intel) and personal MacBook Pro (m1) and sometimes I plug the 2 together using a thunderbolt 3 cable (only one connected to a charging cable). Both charge and internet sharing/networking also works.
- fps_doug 4y ago
  Does it matter which one is connected to the charger? If not, that would mean they adjust that "power level" value they send over the other port which is used to determine who charges who. While it would perfectly make sense to implement it that way, I'd also be surprised that manufacturers actually do.
  - johnwalkr 4y ago
    I don't know, I didn't think about or try to see what happens when both are on battery power. I don't see how they could negotiate with each other based on battery level from my knowledge of how usb PD works. I do know that macbooks only accept one (the highest rated) power input, so when one is plugged in, it will also charge from the plugged in macbook to the other one. When trying to google for the answer, I noticed a lot of misinformation about this topic, and it doesn't seem well-known that thunderbolt can be used for networking data transfer instead of "target disk mode", which is not even support on Mx macs. Anyway, finally I found a convincing answer: It depends on the order of plugging in the cable and the first mac will plug in the second![1] This is great, the user gets to decide, and I am glad you asked this question! [1] https://www.youtube.com/watch?v=hV-zqi_ztw0 https://www.youtube.com/watch?v=hV-zqi_ztw0
antipaul 4y ago
Which MBP model? I think it may matter
musicale 4y ago
> two macbook pros IIRC the second one you plug in charges the first. You can also charge from a single MacBook Pro that is plugged into a power adapter, in a daisy-chain or star topology.

atemerev 4y ago

famous last words!

johnwalkr 4y ago

I have a work (intel) and personal MacBook Pro (m1) and sometimes I plug the 2 together using a thunderbolt 3 cable (only one connected to a charging cable). Both charge and internet sharing/networking also works.

fps_doug 4y ago
Does it matter which one is connected to the charger? If not, that would mean they adjust that "power level" value they send over the other port which is used to determine who charges who. While it would perfectly make sense to implement it that way, I'd also be surprised that manufacturers actually do.
- johnwalkr 4y ago
  I don't know, I didn't think about or try to see what happens when both are on battery power. I don't see how they could negotiate with each other based on battery level from my knowledge of how usb PD works. I do know that macbooks only accept one (the highest rated) power input, so when one is plugged in, it will also charge from the plugged in macbook to the other one. When trying to google for the answer, I noticed a lot of misinformation about this topic, and it doesn't seem well-known that thunderbolt can be used for networking data transfer instead of "target disk mode", which is not even support on Mx macs. Anyway, finally I found a convincing answer: It depends on the order of plugging in the cable and the first mac will plug in the second![1] This is great, the user gets to decide, and I am glad you asked this question! [1] https://www.youtube.com/watch?v=hV-zqi_ztw0 https://www.youtube.com/watch?v=hV-zqi_ztw0

antipaul 4y ago

Which MBP model? I think it may matter

musicale 4y ago

> two macbook pros IIRC the second one you plug in charges the first. You can also charge from a single MacBook Pro that is plugged into a power adapter, in a daisy-chain or star topology.