Is it possible to charge a Surface Pro 3 via a Powerbank?
April 10, 2016 10:55 AM   Subscribe

Is it possible to charge a Surface Pro 3 via a power bank that only has usb output?
posted by ajayb to Computers & Internet (5 answers total)
Depends on the amperage of the power bank's USB power output. 1.0-1.1Amp, it would charge truly slowly. 2-2.1A will charge at a reasonable clip. That's true for other tablets as well.

It looks like the SP3's battery capacity is 3500 mAh, milliamp-hours; your power bank will also have a capacity rating in mAh, and that'll let you know how many charges or what portion of a single charge you can expect at best from your power bank.
posted by Sunburnt at 11:25 AM on April 10, 2016

Thanks for the reply. I checked the power bank and it is 10,000 mAh, so it has the capacity. The SP3 has a strange proprietary connector and I can't seem to find an adapter from USB to the SP3 connector.
posted by ajayb at 1:19 PM on April 10, 2016

I don't agree with Sunburnt on this. There's some discussion on Reddit about this. It appears that the Surface Pro 3 uses a 12V 36W power supply, while USB operates at 5V. While there is ways of stepping up a voltage to a higher one, I don't think it would work in this case. 36 watts is about 3 amps at 12V, or about 7.2 amps at 5V (assuming a perfect step up converter, which isn't likely to be the case). I've never seen of a USB power bank which can provide more than 2.1 amps of charge current. Even if you had such a power bank, you'd still need to purchase additional electronics to step up the voltage.

So in short, no USB power bank will do it. You can buy power banks designed specifically to charge laptops (which can provide 12V output) - there's some discussion in that Reddit thread I linked above about them.
posted by leo_r at 3:36 PM on April 10, 2016

Seconding leo_r on this one. You're not going to find a USB to Surface power connector adapter not only because they don't exist, but also because USB has different electrical characteristics from what the Surface expects from its power supply. You'll want to get a power bank that is specifically designed to charge your Surface.
posted by Aleyn at 4:11 PM on April 10, 2016

There are external auxiliary batteries for laptops, some of them have adjustable output voltages. Of those, I'd guess that most have a 12v setting. You'll still need an appropriate cable. Prices probably start ~$100.

BTW, mAh an entrenched but problematic measure of battery capacity because it doesn't take into account the battery or device voltage. Watt/hours is better, which is generally calculated by the charge capacity * nominal voltage of the battery pack. For traditional USB powerbanks, nominal voltage is that of a single Lithium ion battery (typically) 3.7v. For the Surface Pro 3's battery, it is 7.4v.

Note, Qualcomm QuickCharge supports higher charging voltages, up to 12v in v2, and 20v in v3, but you I don't think the spec gets you to 36W, and you'd still need a specialized adapter cable.
posted by Good Brain at 5:31 PM on April 10, 2016

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