Case study · T-Mobile

Choosing a wireless charging path for T-Mobile phones

I led T-Mobile's 2009 evaluation of wireless charging suppliers for phone battery covers.

Role: Producer and innovation strategist
Organization: T-Mobile
When: May 2009 to Aug 2009
Platform: Mobile hardware accessory, T-Mobile HTC Magic / MyTouch

HTC device with WildCharge receiver cover, showing 1.8mm thickness specification

In short

01T-Mobile needed to decide which wireless charging product to test and potentially release, and the cover had to keep USB access.
02As producer and innovation strategist, I led the vision and the project, compiled the supplier RFI and directed the design explorations.
03We narrowed the field to PowerMat and WildCharge and defined an electromechanical solution that kept USB access, as an accessory exploration.

requirements / specs
competitive analysis
surveys · 502 respondents
personas · by PowerMat
design explorations / directions
industrial design

01Opportunity

Four suppliers offered wireless charging, each with different trade-offs

In 2009 at T-Mobile, I led an accessory exploration for a wireless charging battery door and mat for the HTC Magic / MyTouch, using induction charging.

PowerMat, WildCharge, Mojo Mobility and Fulton/eCoupled each had trade-offs in thickness, efficiency, data transfer and price. The cover also had to keep USB access.

The work sat with T-Mobile's Creation Center and Advanced Innovations team, and fed a go/no-go decision that involved tooling costs and the risk of looking late to market. As producer and innovation strategist, I owned that evaluation.

Black wireless charging pad, angled product shot showing form and finish — Black wireless charging pad, shown to set out the form of the mat accessory under evaluation.

02Hypothesis

A custom cover could charge and still pass data

The bet was an induction-charging battery door and mat for the MyTouch that kept the phone's design and its USB port for file transfer.

The physics set the limits. PowerMat needed a 1.6-2.4mm air gap, so 0.8-1.2mm of wall above the coil, and no metal between the coils. The design also had to keep the MyTouch design equities, with Mike Kemery, iD Lead, advising on industrial design.

Suppliers' stock designs would launch publicly on Oct 4, so any test needed a custom design. Mutual NDAs dated June 29, 2009 governed what we could share with PowerMat and Matchbox Mobile. Joseph Ungari, VP Advanced Innovations, signed them, and I was the Creation Center contact.

PowerMat receiver integrated into T-Mobile phone device — PowerMat's receiver integrated into a T-Mobile phone, showing how its charging hardware sat in the device.

PowerMat's slim receiver render, showing the thickness the cover design had to work around.

White inductive charging receiver, 3D render from isometric angle. — Inductive charging receiver render from an isometric angle, part of the design exploration I directed.

03Experiments

An RFI and design studies narrowed four suppliers to two

I compiled the RFI that went to suppliers. It covered a coil in a custom battery cover, a wall charger spec, and immediate-term and long-term OEM tracks.

Mojo Mobility and PowerMat responded, and WildCharge delivered a concept deck. We narrowed the field to PowerMat and WildCharge, then compared their material against T-Mobile retail data. I compared them on thickness, efficiency, data transfer, price and commercial terms.

PowerMat ran an online survey of 502 people and supplied personas of its target consumers. Those informed our view of users.

I led the design and directed the Bubbles and Circles back-panel graphic explorations for the door. As Technology Lead, I managed the first relationship with WildCharge, and we worked with them and internal resources on electromechanical feasibility.

White inductive charging pad with bubble texture surface treatment. — Bubbles back-panel graphic treatment on a white charging pad, one of the explorations I directed.

White charging pad with circular texture pattern, alternate angle. — Circles back-panel graphic treatment on a white charging pad, shown from an alternate angle.

04Learning

Retail mix pointed to a two-position mat

T-Mobile's retail mix favored a 2-position mat for a phone plus a Bluetooth headset.

We compared the two candidates side by side. WildCharge was cheap and first to market but older and less efficient. PowerMat offered a better form factor and data transfer. Neither clearly won.

Thickness of the receiver and cover emerged as the central design constraint. PowerMat's survey also gave us open-ended answers from non-interested respondents, who pointed to cost, space and lack of perceived advantage.

Bulleted list of survey responses from PowerMat non-interested respondents showing cost, space, and functional concerns. — PowerMat's survey responses from non-interested respondents, naming cost, space and lack of perceived advantage as barriers.

05Decision

We proposed testing a custom design, not picking a winner

We proposed that any test use a custom design, not a supplier's stock design. That meant more design work and tooling. The plan targeted a 2-position mat for a phone and a Bluetooth headset.

So I framed the choice as how to test a custom design, head-to-head or single, rather than which supplier to pick outright. We also proposed thickened-door and step/smooth back studies, and web sales and PR to limit confusion if both products were released.

The WildCharge work produced an electromechanical solution integrated with the MyTouch design that kept USB access. I wrote the WildCharge feasibility summary. The in-home head-to-head test and limited in-store trial were proposed only.