E-bike batteries are, for the most part, a collection of 18650 batteries, packaged together and welded in series and parallel, attached to a battery management system (BMS). A "dead" e-bike battery may only have two or three truly dead cells inside, while the remainder work fine. This is useful knowledge that, for the most part, very few e-bike owners can really use. Arc welders are not a common tool to own, and most e-bike batteries are not designed to be opened, safely or otherwise.
French firm Gouach, essentially a three-person company, is pitching its Infinite Battery as the opposite of this status quo. It's a durable, fireproof casing into which you can place and replace 18650 batteries using only a screwdriver. It keeps you updated on the status of cell performance and heat through a Bluetooth-connected app. And it's designed for compatibility with "90% of existing e-bike brands," or you can upgrade an existing "acoustic" model.
Credit: Gouach
Circuit boards, bent to riders’ will
Alexandre Vallette, CEO of Gouach, told Ars that developing a system for no-weld battery wiring involved "a lot of trial and error" over four years. A typical "spring" contact for an 18650—the kind used by most devices that take AA or AAA batteries—doesn't work, because bike rides can knock them loose with vibration. What emerged were custom-printed circuit boards (PCBs), with just-flexible-enough contacts cut into the board to carry the current from each battery to the BMS, allowing for thermal monitoring across numerous points on the package.
The Infinite Battery's case, too, was born of hard-won experimentation. Gouach provided early versions of its refillable batteries early on for a European bike-share company, using an off-the-shelf "shark"-style casing. Like anyone who lives in a city with dockless bike-sharing, they discovered the variety of places and angles at which people will leave a shared bike. Water ingress killed a number of bike batteries.