(EU) 2023/1542 · Annex XIII(4)(a) -> Annex IV, Part A(4)
Energy round trip efficiency: who decides it is not applicable
Of the five parameters in Part A of Annex IV, this is the only one with a qualifier. Point 4 reads where applicable, which looks like an exit — until you look at the public tier. Point 1(n) of Annex XIII asks for initial round trip energy efficiency and efficiency at 50% of cycle-life, with no such qualifier attached. So a manufacturer who concludes the Part A parameter is not applicable has not disposed of the public field, and has usually written the reasoning for that conclusion nowhere at all.
What the where-applicable qualifier does
The Regulation does not say who judges applicability or against what test. A general filter exists at passport level: the fourth subparagraph of Article 77(2) provides that the information is included to the extent applicable to the category or sub-category of battery concerned. On top of that, the qualifier in point 4 of Part A attaches to this parameter specifically. In practice the conclusion is your judgement, and the only place to justify it is the explanation in the technical documentation under Article 10(1).
The definition measures the battery in a test
Point 6 of the introductory part of Annex IV provides that energy round trip efficiency means the ratio of the net energy delivered by a battery during a discharge test to the total energy required to restore the initial state of charge by a standard charge. The reference is therefore the battery inside a test sequence. A whole-system efficiency measured at the AC terminals with all conversion losses included is a different number and does not belong in this field, however much more meaningful it is to a buyer.
The percentage is a calculation, not a reading
Because it is a ratio of two measured energies, this field pulls in point 5 of Part B of Annex IV: any calculations performed with the measured parameters. For an authority that means the path from two measurements to one percentage has to be visible — which energy was read during discharge, which during charge, and what was treated as a standard charge.
Fade, and the public value at half of cycle-life
Point 4 of Part A asks for the efficiency and for its fade. Public point 1(n) instead asks for two specific values: the initial figure and the figure at 50% of cycle-life. The second cannot be computed; it only comes out of a cycle-life test that ran far enough. A test stopped at start of production does not produce it, and it cannot be obtained retrospectively.
Where it goes wrong
- Concluding the parameter is not applicable without recording the reasoning in the Article 10(1) explanation.
- Reporting system efficiency at the AC terminals instead of the ratio defined in point 6 of the introductory part of Annex IV.
- A single value, although public point 1(n) asks for the initial figure and the figure at 50% of cycle-life.
- A percentage with no visible calculation from the two measured energies, required by point 5 of Part B of Annex IV.
Frequently asked
Who decides that the parameter is not applicable?
The Regulation sets no criterion. The fourth subparagraph of Article 77(2) says only that information is included to the extent applicable to the category or sub-category of battery concerned; the judgement and its justification are yours to record.
May I state system efficiency?
Not for this field. Point 6 of the introductory part of Annex IV defines the ratio of net energy delivered during a discharge test to the energy required to restore the initial state of charge by a standard charge.
What does the public tier require?
Point 1(n) of Annex XIII requires initial round trip energy efficiency and efficiency at 50% of cycle-life. That point carries no where-applicable qualifier.
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