Audi A8 D3 - starting engine on the dead battery using portable car battery pack
 

Hi everyone :) Recently, the battery in my friend's Audi A8 died so I thought he had to go home on his legs. But he has very interesting device - a battery pack (like smartphone battery packs). He connected this device with the Audi battery using cables and started engine. I recorded this action and I want to show this.

I'm thinking about buying this device.