USB charging safety.

[Razorbill]

I often use my uMBP15 (2010) to charge my phone or ipod overnight when the computer is in sleep mode.

The question is, what would happen if the power supply from the adapter for some reason got cut off or it got unplugged. I have seen that it keeps charging while on battery, but is there some protection from having the computer battery completely discharged?

 

[snaky69]

The computer will sleep past a certain charge %.

You can't charge anything in sleep mode, you're probably using what'd called clamshell mode(lid closed, computer still turned on).

 

[Razorbill]

The ports do stay powered in sleep mode, both when selecting Sleep from the menu and when just closing the lid (computer/fans off).

I suspect that it will cut the power to the ports when the battery is getting low. I'll try it next time my battery is low to see when/if it cuts off.

 

[Big-TDI-Guy]

The battery itself should have a built in LVD independent of the computer management. As undercharging beyond a certain point will damage the battery / drastically alter its capacity for good. Most packs have a controller that will cut out in over charge, under charge and over temp conditions - and downstream devices have no say in the matter.

 

[Razorbill]

I tried to check it today. While I was on battery it was still charging the phone down to 14%. I didn't want to run it any lower, so unfortunately I never found if/when it will cut out.