The ZMI PowerPack 20000 is the most useful backup battery you can buy. It packs a huge, 20,000mAh battery that can power a MacBook and two other devices at the same time. Plus, you can quick charge it via USB. And it can even work as a USB data hub.

This 14.29-ounce (405 gram) brick might be overkill for daily juicing of your iPhone, but for everything else it’s amazing.

ZMI PowerPack 20000 review: One big battery

The ZMI PowerPack 20000 is essentially a huge battery wrapped in a blue-black aluminum skin, with three ports and a button. You use its single USB-C port to charge the unit, and to charge your MacBook or iPad Pro (via USB-C cable). Two USB-A ports can charge any other USB device.

The maximum output tops out at 45 watts. That’s powerful enough for a MacBook, and more than enough to charge the iPad Pro while in use. Because you charge the battery itself via USB-C, charging is fast. You can go from full to empty in a little under four hours.

USB data hub

So far, it’s not really any different from any other USB-C battery pack. But the ZMI PowerPack 20000, which retails for about $70, also works as a USB data hub. Plug your Mac (or iPad) into the USB-C port, then plug a mouse, a USB drive, an SD card reader, a MIDI music peripheral or anything else, into the other two ports, and they will be connected to your computer. To activate the data feature, just double-tap the button on the side of the device.

This is pretty amazing. It means you can use any peripherals while also charging your computer, anywhere you like. On a recent super-long train journey, I used the ZMI to connect the Teenage Engineering OP-Z synth to my iPad. It worked perfectly as both a MIDI connection, and as a USB audio connection. And when iOS 13 arrives and adds USB storage capabilities to the iPad Pro, you’ll be able to hook up storage, too.

Clean power

One other neat feature: USB battery power is clean. If your audio gear buzzes when you connect it together and power it from a regular USB charger, try using this battery pack instead. I find it eliminates buzz, while still keeping everything charged.

The ZMI comes with a little microfiber pouch, and a couple of USB-C cables (one doubles as a micro USB cable). Put this and a USB-C power brick in your luggage, and you’ll be covered for everything.

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