Expected lifetime: cycles, calendar years and the warranty trap

Estimation is allowed; unsupported estimation is not

The second subparagraph of Article 10(1) speaks of the technical specifications, standards and conditions used to measure, calculate or estimate the values. Estimation is therefore expressly on the table. The same sentence requires the explanation to sit in the Annex VIII technical documentation and to cover at least the elements of Part B of Annex IV. A forecast with no recorded basis is not a discharged obligation but an unproven claim, and a hard one to defend under inspection.

Two units resting on two different bases

Cycles come out of a cycle-life test, whose depth of discharge the documentation must explain under point 3 of Part B of Annex IV. Calendar years come out of a calendar ageing model — accelerated testing and extrapolation. Those are separate procedures carrying separate uncertainties. One number divided by an assumed cycles-per-year figure does not cover both; it says what the second unit would follow from the first, not what happens to the battery while it sits.

The carve-out applies to cycles only

Point 5 of Part A of Annex IV asks for cycles except for non-cycle applications. That carve-out reaches half of the parameter. Calendar years are still required where cycles make no sense — standby power that spends most of its life sitting charged, for instance. Leaving both units blank is therefore not the correct consequence of the exception; it is two missing values where one was excused.

A warranty period is not a lifetime

Three related numbers sit close together in Annex XIII and get mixed up routinely. Point 1(j) asks publicly for expected battery lifetime in cycles and the reference test used. Point 1(m) asks for the period for which the commercial warranty for the calendar life applies — a commercial commitment, not a technical forecast. Point 5 of Part A of Annex IV asks for cycles and calendar years for the individual battery. Copying the warranty period into that last field is a substantive misstatement, not a shortcut.

A change of status resets the figure

Point 4(a) of Annex XIII requires the Article 10(1) parameter values when the battery is placed on the market and when it is subject to changes in its status. For a repurposed or remanufactured battery that means a lifetime figure for the new application, not the original figure carried across. Article 45(2) makes the same point from the other direction: the economic operator must take into account that such operations may put the battery in a different battery category.

Where it goes wrong

• Forecasting calendar years with no recorded basis; Article 10(1) permits estimation but requires the method to be explained.
• Deriving calendar years from cycles and an assumed usage pattern as though it were the same measurement.
• Invoking the non-cycle carve-out for calendar years as well — it reaches cycles only.
• Copying the commercial warranty period from point 1(m) as the expected lifetime.
• Carrying the original lifetime across to a repurposed battery, although point 4(a) requires fresh values on a change of status.

Frequently asked