Safety first

December 9th, 2016

At EUHA, customers were excited about Cellion, our first hearing aid using Li-Ion batteries in combination with inductive charging. But they also asked us how we ensure its quality and even more important its safety? As always: by testing, testing, testing and, again, by testing.

Safety is key from the very beginning
Product safety is considered from the initial concept onwards. Cellion uses a ‘power module’ which consists of the Li-Ion battery cell plus the power management integrated circuit. These components are located in a stable and closed ferrite casing. The ‘power module’ circuit handles safety specifications and features such as over voltage, charging current, internal short circuit events etc.
The inductive charger regulates the power transmission to the power module via a magnetic inductive coil. A communication protocol between ‘power module’ and charger monitors the state-of-charge and the temperature of the Li-Ion battery cell throughout the charging process. This protocol also ensures that Cellion can only be charged with our inductive charger.

Usability Testing
In cooperation with the Technical University Ilmenau, functional prototypes were tested for their usability. Based on the feedback from hearing care professionals as well as hard of hearing, improvements were triggered.

Testing with first out of tooling parts
As soon as the very first Cellions were available, internal tests were started. Thus we detect early on product shortcomings and modify the charger and the hearing system accordingly.

Testing the Limits
As soon as the first real prototypes were available, tests intensified. The focus was on life cycle tests under stress conditions (e.g. life cycle of Li-Ion cell at 45°C in the heat chamber) as well as destructive tests (how hot can the cell become before it explodes?). These destructive mechanical abuse and extreme high temperature (> 150o C) tests have been conducted in an external, specialized laboratory.

Supplier Management
The cooperation with the supplier of the power module and the inductive charger also plays an important role for quality assurance. Next to weekly meetings during the development phase, an audit of the production facilities was conducted by R&D and Quality engineers. They inspected the supplier’s factory processes, improved identified weaknesses and traceability performance.

After Launch Monitoring
During the first year after launch all returned Cellion devices are inspected in detail. This helps to identify possible flaws in the product and the associated production processes. This close monitoring will result in another high quality product and even better: It gives us ideas how to further improve in the next generation.

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