The brainiacs over at Anandtech have been experimenting with the Nintendo Switch to get to the bottom of how much power it draws, and what kind of portable batteries you'll need to charge it when you're out and about.
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Looking at the Switch power adaptor and dock gives some background information, but remember it's far more powerful than the Switch alone requires. The AC power adaptor for the Switch is quite beefy--more powerful even than the USB-C charger that comes with Apple's latest Macbooks--at 15 volts at 2.6 amps, which works out to a total of 39 watts. This is far higher than the dock's USB-C output (only used for charging the Switch tablet and attached Joy-Con controllers), which is rated for 15 volts at 1.2 amps, or 18 watts. The reason for this is because the dock also has three USB Type-A ports, including one USB 3.0 port on the rear. The AC power adaptor, therefore, needs to be able to provide enough power to not only charge the Switch, but potentially also run a USB hard drive, and charge two Switch Pro Controllers concurrently.

According to the analysis, when undocked and connected to a USB battery pack, the Switch will draw a maximum of 9.1W, or 4.68V at 1.94A. This means that to charge the Switch, you'll need a power bank that can deliver 5V at 2A or better. As always with battery-based devices, it's always best to buy good quality devices, so do your research.

Finally, it's worth noting that the Switch can't meaningfully charge during gameplay while connected to most USB power banks. This is due to the inner workings of the USB Power Delivery specification, which you can read about in an intimidating amount of detail in the source article.

http://www.anandtech.com/show/11181/...-consumption/3

source: gamespot

Maybe its good to know if you plan to buy an Switch Console, or already have bought one and want to use it on the go.