State of health across a second life

State of health across a second life is the dated measurement of the remaining capacity and performance of a battery at each transfer to a new application, recorded so the new application can be judged on measured condition rather than on age alone. State of health is commonly expressed as a percentage of a reference capacity, but the percentage is meaningless without the reference, the test method, the temperature, and the date. The record must state those elements at the end of first life, at assessment for second life, and during second life use. A battery that shows a high state of health on one method and a low state on another has not been measured twice; it has been measured under two different conditions, and the record must say so.

State of health means the assessed condition of a battery relative to a stated reference, usually rated capacity at manufacture, under stated test conditions. The scope covers measurements at first life end, second life assessment, and second life use, for the battery or module stated.

What is the legal frame for this stage?

State of health across a second life is not a single event at the end of a battery life. Articles 10 and 14 should be read with the definitions in Article 3, because the category of the battery decides which collection and treatment duties apply. An assessor measuring capacity retention for EV modules entering stationary use needs to know the category before any other check, since a portable battery, an LMT battery, an EV battery, and an industrial battery follow different routes. A module with 82 percent capacity retention under a slow discharge test at room temperature should be recorded with the test rate, temperature, and date, so a later test under different conditions can be compared honestly.

How are handovers recorded?

For state of health across a second life, the handover record should also state the condition of the battery, the reason for transfer, and any safety information passed with it. Test reports, method notes, and dated measurements should be retained for each transfer, including consignment notes where waste law requires them. An assessor measuring capacity retention for EV modules entering stationary use should check that quantities at receipt match quantities at dispatch, allowing for the measurement method stated in the record.

How are targets stated and checked?

For state of health across a second life, the relevant target may be a collection rate, a recycling efficiency rate, or a material recovery rate, and each target has its own calculation method, reference period, and chemistry scope. Access to battery management system data for state of health assessment is addressed in Article 14 and Annex VII, and the record should state the data source and the access route used, without claiming access that was not available. An assessor measuring capacity retention for EV modules entering stationary use should record the source of each figure and the date on which the figure was checked, using a dated snapshot where a figure can change.

How are safety and classification decided?

State of health across a second life may involve a battery that is damaged, swollen, leaking, or otherwise in a condition that changes handling, and the record should state the condition found, the test or inspection applied, and the decision that followed. A module with 82 percent capacity retention under a slow discharge test at room temperature should be recorded with the test rate, temperature, and date, so a later test under different conditions can be compared honestly.

What belongs in the passport entry for this stage?

For state of health across a second life, the entry should show the stage reached, the operator responsible at that stage, the date of the stage, and a reference to the underlying evidence, without adding a claim about a later stage that has not happened. Test reports, method notes, and dated measurements should be linked by identifier, so the passport entry, the handover note, and the treatment record refer to the same battery. An assessor measuring capacity retention for EV modules entering stationary use should check that the passport entry is updated when the stage changes, and that an earlier entry is preserved in version history rather than overwritten without trace. Access to battery management system data for state of health assessment is addressed in Article 14 and Annex VII, and the record should state the data source and the access route used, without claiming access that was not available.

What stays open, and how is it followed up?

For state of health across a second life, open items may include a missing handover note, a pending test result, a facility report not yet received, or a delegated act not yet published that will set a method or a format. An assessor measuring capacity retention for EV modules entering stationary use should list each open item, name the owner, and give the next review date. A module with 82 percent capacity retention under a slow discharge test at room temperature should be recorded with the test rate, temperature, and date, so a later test under different conditions can be compared honestly.

How are two state of health figures compared?

Two figures are compared only when the reference, the method, and the conditions match. A figure of 85 percent from a slow capacity test at room temperature and a figure of 78 percent from a model based estimate at a different temperature describe the same battery under different conditions, and the comparison must state that difference. A worked comparison table shows the two figures side by side, with method, reference, temperature, rate, and date for each, and a note on whether the difference is a real change or a method difference. A trend is drawn only from figures measured under the same method, and a figure from a new method starts a new trend, with the method change recorded.

State of health is a measurement with conditions, and a percentage without conditions is a number without a record behind it.