Will Kail's profile

Bunk - The wireless smartphone battery

Industrial Design

Bunk is a 100% wireless, hot-swappable battery pack, that snaps magnetically onto the back of your smartphone, providing almost double the longevity without the permanence of battery cases or the awkwardness of separate power banks. 
Bunk can simply be popped on when needed over the course of the day - and best of all, Bunk works on any QI enabled smartphone, case or not.


80% of smartphone users actively take measures to extend their battery life throughout the day, while most smartphones are released with non-removable cell, forcing users resort to using various inelegant solutions to extend the lives of their devices.

Current Solutions

Power banks are the most popular solution to on-the-go charging, however require a tethered connection and a pocket or second hand to hold the unit, making them clumsy for use while mobile.
Battery cases integrate the battery and smartphone, however are phone specific, raising costs to consumers, the battery is also non-removable even when empty, resulting in a bloated size.
Mains Quick Charging solutions offer a large boost in exchange for time spent stationary, however research shows that most users are not especially forward thinking and do not value battery life until their devices reach <30%, at which point they may struggle to find a power socket, or have the time to spend stationary.


Various approaches to the problem were addressed, from encouraging behavior change to remind users to charge their power banks when low, to power bank-QI charger hybrids to simplify recharging steps and use while mobile.


Proof of Concept

Various aesthetic prototypes were made from foam and MDF to evaluate size and in-hand feel, while a functioning prototype investigated the performance of the magnets and reliability of the charging system.


For the 79% of smartphone users who use a case [1], the magnetic bunk sticker is simply stuck onto the inside of their case. For the minority who do not use a case, it can alternatively be stuck directly onto their phone.

High strength neodymium magnets locate and secure bunk in place.

Multi-Coil solution intelligently selects the optimal output coil, allowing bunk to align with the receiver coil on any modern smartphone.

Bunk is recharged via a QI receiver in its front casing, and supports 'pass through charging' to the user's phone, allowing both devices to be charged together with a single QI pad. An intelligent charging IC will prioritise charging the phone prior to charging bunk.

Bunk is IP67 rated, so you can take it anywhere your smartphone goes.

Three textures and eight colorways to compliment a wide range of case colors and styles.


Thanks for checking out Bunk.
Keep an eye on my profile for more work over the coming months.
I also keep an active design Instagram over at www.instagram.com/willkail
Feel free to drop a message below if you have any comments or questions, I love hearing others' thoughts.

Bunk is now available for pre-order on getbunk.com

Bunk - The wireless smartphone battery

Bunk - The wireless smartphone battery

Bunk - A wireless smartphone battery