Can the 100W power bank damage the battery of the pc?

federikowsky wrote:

I've a MacBook Pro 14 2021. I would like to buy a power bank to charge the macbook when I am away from home for a long time. I saw that the 96W adapter has 20.5v and 4.7A, if I took a 100W powerbank (20v and 5A) would I damage the pc? What details should i consider to buy a good powerbank?

I have heard of no issues.

MacBook Pro (14-inch, 2021) - Technical Specifications

Simply asserting a charging voltage against one of the interface(s) will NOT successfully charge your MacBook Pro.

An external power supply that provides "USB Power Delivery" (like certain displays) must negotiate over the USB cable using USB Power Delivery Protocol, and can not 'force itself' on your Mac. The Voltage and Current are delivered only after your Mac requests and the charger agrees to supply power under certain controlled conditions. The computer is in control of the entire process.

I've got a Mophie Powerstation 8000 which has a USB-A and USB-C port. The USB-C port is also used for input power. I don't know if it's strictly considered USB-PD, but the USB-C output is rated at 5V/3A.

This is what I see with the USB-A (with a USB-A to USB-C cable):

This is what I see with the USB-C (and USB-C/USB-C cable):

It's kind of odd because it's clearly a DC power source. I suppose that's what they call any external power source, assuming that it has to be converting from AC.

It shouldn’t. However, most USB-C cables are limited to 3A with some circuitry that signals if it’s capable of higher current. The charging is controlled by the computer, and external power is just a current limited power source more or less. The charging circuitry inside the Mac will control the charging current.

External power sources don’t force their maximum power to devices. They provide a voltage with a current limit, and the device will use what it controls up to the limit. This is the same as anything that takes power. A night light that’s rated at 0.05A can be used in an outlet that can provide 20A. That’s just Ohm’s Law (V = I x R) at work.

federikowsky wrote:

in fact the problem wasn't the Amps but rather the Volts. If I'm going to buy 3A PowerBank, it only charge the PC slower, but what about the V ? it's problem if voltage is 20 ?

Most of these cables can handle 20V just fine. It's the current limit that matters in terms of safety. I can use the cheapest USB-C cable to charge any of the computers in my household that take 20V.

The power bank must be a "USB Power Delivery" device. Otherwise NOTHING happens.

The computer will examine the parameters of the proposed power and select an appropriate Voltage and Current and initiate charging if needed. Or if none is acceptable, it will choose none.

Grant Bennet-Alder wrote:

The power bank must be a "USB Power Delivery" device. Otherwise NOTHING happens.

The computer will examine the parameters of the proposed power and select an appropriate Voltage and Current and initiate charging if needed. Or if none is acceptable, it will choose none.

It would be useful, but not strictly needed to provide **some** power. I checked with a USB-A power bank and a USB-A to USB-C cable, and right now System Report is saying that it's providing up to 5W to a newer MBP. Not sure why it's not more. It wouldn't be useful for much other than maybe marginally increasing the run time. Perhaps something like a USB-C power bank can provide 15W. I remember seeing that in System Report when I used one with an USB-C/USB-C cable and USB-C only MBA.

Any power bank you expect to use MUST support

USB Power delivery

If it's a USB Power delivery device, it will work great.

y_p_w has corrected me that any-old power bank can get 5W into your MacBook, but not more. Since MacBook Pro typically are seeking around 100 Watts, 5 Watts is not mush help.