Retina MacBook Pro Not Charging when Plugged into Thunderbolt Display

by Michael on March 14, 2013

I previously reported that my Retina MacBook Pro often won’t recognize USB devices plugged into my Thunderbolt display when waking from sleep. Now I’m having a new problem. It won’t charge when plugged into the display.

Neither of these problems is completely crippling, but they’re extremely annoying given the cost associated with hardware in question. I’ve managed to solve the USB issues (mostly) by plugging in the power supply and waking the rMBP before plugging into the Thunderbolt display.

But, in doing this, I’ve discovered a different problem… The rMBP won’t accept a charge from the Thunderbolt display’s power cable. When I plug it in (using the provided adapter since the rMBP uses a MagSafe 2 plug) the little light on the charger stays dark instead of turning orange or green.

The battery icon in the menu does show that the computer is plugged in but, when I click on it, I’m greeted with “not charging.” Frustrating. There seems to be enough power for the computer to hold it’s charge, but it won’t add anything to a partially drained battery.

I believe that this is a problem with the Thunderbolt display itself and not the rMBP because the computer will take a charge just fine when plugged into a wall charger.

At first I thought it might be a problem of too much power drain when trying to drive both the on-board Retina display plus the 27″ Thunderbolt display (plus some peripherals). I tried unplugging all peripherals with no change.

I then tried unplugging the Thunderbolt cable while leaving the power hooked up. No change. And cranking down the brightness on the built-in display to reduce power consumption doesn’t help, either.

This is an extremely frustrating problem. My next step will be to reset the SMC on the off chance that the computer is at fault. I tried this the other day but nothing seemed to happen. This is perhaps because I didn’t have a wall plug at my disposal (instead I was plugged into the display) so I will need to try again at home.

Update: On a whim, I tried putting the computer to sleep. When I unplugged and re-plugged while asleep, the charging light came on. And when I woke it up, it stayed on (orange while charging, switching to green when full).

Given the above, it appears that the power supply in the display is barely strong enough to charge the computer and that putting it to sleep gets power consumption low enough for it to get over the hump and start charging.

This begs the question…

Is the display performing as expected (maybe it’s just under-powered) or is there something wrong and it’s putting out too little power? I’m not sure, but the tech specs say it should provide up to 85W of power, same as the rMBP charger.

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