The example of a lawnmower fuel gauge only lasting for 6 months due to a non-replaceable battery would definitely fall under the durability/repairability clause. It would count as a defect that existed at the point of manufacturing, not that it sounds like that even matters.

https://eur-lex.europa.eu/legal-content/en/TXT/?uri=CELEX:32...

> In order for goods to be in conformity, they should possess the durability which is normal for goods of the same type and which the consumer can reasonably expect given the nature of the specific goods, including the possible need for reasonable maintenance of the goods, such as the regular inspection or changing of filters in a car

> Given that when implementing Directive 1999/44/EC, a large majority of Member States have provided for a period of two years, and in practice that period is considered reasonable by market participants, that period should be maintained.

> For a period of one year, or for a period of two years if Member States choose to apply a two-year period, the consumer should only need to prove that the good is not in conformity, without also needing to prove that the lack of conformity actually existed at the relevant time for establishing conformity