The press release has a bit more about their own power testing:

The MixBox 2 also can be powered by the same iOS device – which means that battery power is a consideration when using it – or you can also use the micro USB port to power it instead of draining your phone. Then plug in your iPhone/iPad/iPod touch to the MixBox 2 (the iOS device is where the actual mix is being stored) via a 7 pin DIN to Apple Lightning cable. To set it up, plug in a pair of RCA cables from the Record Out on a DJ mixer. The MixBox2 is pretty simple: it’s a dedicated device designed to be a simple plug-and-play recorder for DJ sets. Price: £75 / ~$95 on Indiegogo for first 50 retail/future pricing £95 / ~$119.Availability: 250 units available via an Indiegogo campaign in February, delivered in March 2017.MixBox2: Recording DJ Sets With Your Phone A new device, MixBox2, aims to bring a portable, rapid solution to record DJ sets right onto your phone, and publish them online. Setting up a digital recorder, checking levels, making sure you have the right cables, batteries, etc is only half the battle. One of the more annoying processes in the current digital DJ world is recording, processing, and publishing a mix or live DJ set.

Mixbox ipad