System Report - AC Charger Information - Wattage (W)

Question

System Report - AC Charger Information - Wattage (W)

Why the wattage in the report switch from 86 W to 15 W to 7 W ? what trigger the change?

Should always be the same?

I have noticed that the the state of charge of the battery depleted or full, charging or not, does not affect the wattage.

I have also notice that when the wattage is low 15 or 7 the battery charge start going down arriving at the point of not being able to restart the MacBook Pro 15.

Resetting the SMC and NVRAM may restart the computer, recovering the full charge and the complete operation, but after few day of use may happen again. Icon in the status bar show connected to power supply, even if it is not charging, condition seems to get worst when using the discrete graphic card.

It happen using multiple power supply.

MacBook Pro 15”, macOS 10.14

Posted on Jun 17, 2019 2:53 PM

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Answer 1

Jun 26, 2019 1:31 PM in response to Grant Bennet-Alder

The update 10.14.5 introduce something different that compromise my MacBook Pro. After I performed a clean install, I used the MacBook Pro as before, it has been working with no problem since.

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Answer 2

Jun 18, 2019 6:33 AM in response to giorgio from Parma

The power is changed in steps. The basic step -- available without negotiation, is about 7W at 5 Volts.

This information you see says that power delivery is set to the default, lowest setting.

If you would like to learn more about USB power delivery, this article may help:

https://en.wikipedia.org/wiki/USB_hardware#PD

.

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Answer 3

Jun 17, 2019 10:09 PM in response to Grant Bennet-Alder

I have an update, when the MacBook Pro is not connected to the power supply, the icon show Power source: Power adapter, and the system report under Power, AC Charger information show: connected, 7 W.

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Answer 4

Jun 17, 2019 5:58 PM in response to giorgio from Parma

Your MacBook Pro uses three different micro-controllers to negotiate and re-negotiate the charging rate: the System Management Controller (SMC), another in the battery, and another in the power adapter.

You can see that the power adapter name remains "87 Watt USB-C Power adapter". The micro-controllers decide what wattage is needed, and that is what the power adapter supplies at that time. For example, when the battery is nearly charged, the wattage required will be re-negotiated lower.

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System Report - AC Charger Information - Wattage (W)

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