Shrinking the Power Source
Smart glasses such as the Ray-Ban Meta and Oakley Meta Vanguards have to run cameras, speakers, AI workloads, and sometimes a display — all from batteries tucked inside the temple arms. The challenge is fitting enough energy into a space narrower than a pinky finger, and conventional battery design can't get there.
Meta engineers Karthik and Myuran discussed the company's steel can battery technology on episode 86 of the Meta Tech Podcast, explaining what had to change in battery architecture to power current and upcoming wearables.
Why Pouch Cells Don't Fit
The pouch cells used in phones and laptops are hard to reshape at the scale glasses require. Folds in the packaging waste volume, manufacturing tolerances eat into precious millimeters, and at smaller sizes pouch cells can struggle to deliver peak power when the device is multitasking — for example, recording video while an AI model processes a request.
A smart glasses battery needs to claim every micron of available space, which means it must be rigid and precisely dimensioned to fit the product, not the other way around.
Rethinking the Steel-Can Cell
Steel-can batteries are nothing new — they power tools and watches have used them for years. But Meta's AI glasses needed widths as narrow as 7mm, a scale the form factor had never been built at. Achieving that meant redesigning nearly every internal component.
Traditional steel-can cells use a wound "jelly roll" of electrode material. Meta's engineers swapped that for die-cut stacked layers, an arrangement analogous to wiring small resistors in parallel. The benefit is dramatically lower impedance, which prevents brownouts when the device demands high power from multiple subsystems at once.
Precision is the other major advantage. A steel-can cell maintains its shape to roughly 100 microns, and on a 10mm-wide battery that reclaimed tolerance translates directly into usable volume, higher energy density, and longer runtime.
Capacity Gains Across Generations
Battery capacity for the Ray-Ban Meta grew from 160 mAh in the first generation to 210 mAh in the second — a roughly 30 percent increase. But the product shipped with claims of double the runtime, and chemistry wasn't the reason. The additional gains came from system-level efficiency work across hardware and software: better power management, tighter firmware control, and a form factor that accommodated a larger cell.
The Oakley Meta Vanguards brought a new complication by placing a battery in each temple arm. The cells themselves are symmetric, but the electronic load across the two sides isn't balanced, introducing cross-charging risks and sequencing complexity during boot and shutdown that spans electrical, firmware, and mechanical engineering.
The Meta Ray-Ban Display glasses then introduced the most demanding power profile yet. Unlike bursty camera or AI use, the screen draws sustained power, which pushed the team to design a 248 mAh steel-can cell — the largest in Meta's lineup.
Beyond Smart Glasses
The ultra-narrow steel-can approach developed for smart glasses is proving adaptable to other device categories in Meta's hardware portfolio. The company is focused on scaling the technology across multiple vendors to build a resilient supply chain for the next generation of wearables.
The full conversation, available on the Meta Tech Podcast, goes deeper into the two-battery cross-charging problem, how software and hardware iteration cycles differ, and the realities of cross-time-zone collaboration in bringing a new battery form factor from first sketch to global shelf.
