(EU) 2023/1542 · Annex XIII(1)(n)
Round trip energy efficiency: the second value is the trap
For this field the regulation asks for two values, not one. The first is a straightforward measurement on a new battery. The second requires either a battery that has completed half its cycle-life or a model that predicts it. Miss that in time and you find out only when the test can no longer be completed before the deadline.
What the text actually requires
Point 1(n) of Annex XIII requires the initial round trip energy efficiency and the efficiency at 50% of cycle-life. The conjunction is not decorative: these are two separate values describing how much energy the battery loses when new and how much after half its life.
Why the second value is hard
If a battery lasts 6,000 cycles, 50% of cycle-life is 3,000 cycles. Such a test runs for months to years. In practice the value comes from accelerated ageing or from a model that must be explained — Part B of Annex IV requires any calculations performed with the measured parameters to be stated.
The same figure appears once more
Part A of Annex IV requires energy round trip efficiency and its fade, where applicable, among the performance parameters. That obligation has applied since 18 August 2024, so longer than the passport deadline. Anyone who has already prepared the Article 10(1) document probably holds this value already.
Where it goes wrong
- Entering only the initial efficiency — the field requires both values.
- A modelled value at 50% of cycle-life without the method explanation from Part B of Annex IV.
- Ordering the test too late for a result to exist before the deadline.
- Overlooking that Article 10(1) has required the same value since 18 August 2024.
Frequently asked
Which two values are required?
The initial round trip energy efficiency and the efficiency at 50% of cycle-life. Point 1(n) of Annex XIII requires both.
May the value at 50% of cycle-life be calculated?
In practice it often is, but the method must be explained. Part B of Annex IV requires calculations performed with the measured parameters to be stated.
Does only the passport require this field?
No. Part A of Annex IV requires the same value among the performance parameters, and that obligation has applied since 18 August 2024 under Article 10(1).
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