TAU® 2 - 4in1 emergency keyring power bank



TAU® 2 is the emergency power bank for every device (Lightning, Micro USB, USB-C). Its keyring form factor is perfect to let you attach it to your keys when carrying it around.
Color :
Mercury Black
Ice Gray

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TAU® 2 | A new kind of power bank

Introducing TAU 2 - your trusty, always-charged, universal keyring emergency power bank. Never again will you have to suffer the indignity of your phone giving up on you at the worst possible moment. You’ll no longer need to carry bulky power banks to make important calls 📞, pay with your phone 💳, or use GPS maps 🗺️, even towards the end of the day when your phone's battery is running low. 



You'll never forget to re-charge it

With TAU 2, forgetting to charge your power bank is a problem of the past. Charge your TAU 2 just by putting away your keys the way your mother told you. We even took the time to give you a quick and easy way to set up its charging dock on a desk, on a wall, or even the door side table. Now your power bank is always fully charged and within reach right alongside your keys, eliminating the frustration of a dead battery when you're on the go. Your keys are always in the right place and your power bank is always charged. 🔑🔋



Your keys' new best friend

TAU 2 is so small and compact that it easily fits on your keyring without adding any bulk. The fact that it hooks on your keys means that so long as you have your keys you also have power. The fact that it's always charged means that the Charging Dock will serve as your new tidy place for keys, seamlessly recharging TAU 2 without you even noticing, so it's ready for your next departure. Say goodbye to carrying around a separate power bank with cables in your bag or pocket, or worse, forgetting to bring them with you!  


Battery capacity

TAU 2 may not immediately captivate with its 2000mAh capacity, but it's truly impressive. 🔍 We tested smartphones from major processor producers, revealing three battery improvement ranges: small-battery phones gained up to 54%, mid-battery phones up to 35%, and large-battery phones up to 28%. We calculated these results conservatively, considering battery consumption data from producers, reviewers, and real-life tests, factoring in dispersion and performance decrements due to background apps. Visit the "battery capacity" section on our Kickstarter's TAU 2 page for a detailed understanding of our tests and results!



Key features (4in1)


  1. Charge Lightning devices
  2. Charge Type-C devices
  3. Charge Micro USB devices
  4. NFC/QR code Digital Business Card



Bonus features


  • Pass-through charging (USB-C as input, Lightning/Micro USB as output)
  • QR code lost mode
  • Quick release keychain hook


Designed with love ❤️️ in Switzerland 

    Customer Reviews

    Based on 3 reviews
    Great customer service
    Excellent product

    Excellent product. Very well made and extremely handy.

    Very cool and simple design that’s…

    Very cool and simple design that’s compact and very easily ready for travel at the drop of your hat.

    May have to come back and get a few more for my car, computer and possibly my bike.

    Thanks guys.

    Cristóbal Mena
    Always a great experience

    Quick delivery abroad. Excellent cardboard package, ready to recycle! I've bought several Rolling Square products and backed them on Kickstarter, and they are always top tools for my daily work.

    Always charged. How is it possible?
    The TAU® 2’s magnetic charging dock fixes onto a counter or wall easily, making it effortless to recharge your power back. Just hang your keys on the dock when you get home and the TAU® 2 will be ready to go when you head out next! The integrated cables mean that you can be ready to charge any device at any time. 

    Always with you. What does that mean?
    If standard power banks are too bulky to be carried in your pockets and often left behind, TAU® 2 is so small and light (only 50g / 1.7oz) that you will almost forget to have it with you. 

    Alway ready to use 
    TAU® 2 is compatible with every smartphone and portable device thanks to its two integrated cables:
    • Dual - Patented connector combining Lightning for Apple devices (iPhone 14 & below, iPad, AirPods) + Micro USB (older portable devices / old Android phones)
    • USB-C - Compatible with any Android phone, iPhone 15 & up and newest generation portable devices

    Effortless setup 
    Place the repositionable nano suction layer where you prefer, plug the cable in and TAU® 2 is ready to use. And if you are a DIY aficionado and 100% sure that you aren't going to move your dock, you can also use the screws included in the packaging. 

    • Lightning (iPhone, iPad, AirPods)
    • USB-C devices
    • Micro USB devices

    • Size: 56*x43x19mm (2.2*x1.7x0.7in) *Dimension without hook. Dimension with hook: 63mm / 2.5in
    • Weight: 50g / 1.7oz
    • Capacity 2000 mAh
    • Holdable weight: 690gr / 24oz

    • TAU® 2 Power bank
    • TAU® 2 Dock with USB-C integrated cable
    • Nano suction double-sided layer
    • User manual
    • Eco-friendly packaging

    Custom Tab Content 4

    Frequently Bought Together

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    Mercury Black
    Ice Gray
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