State of Health
Definition
A measure of the general condition of an individual battery relative to its condition when new, expressed through parameters that indicate remaining capability and expected remaining life. Under Article 14 of Regulation (EU) 2023/1542, parameters determining the state of health and expected lifetime of batteries must be contained in the battery management system for stationary battery energy storage systems, light means of transport batteries and electric vehicle batteries, with read-only access for authorised third parties. Annex XIII places state of health among the individual-level information in the battery passport.
Expanded Explanation
State of health is an item-level property, which distinguishes it sharply from most passport content. Composition, chemistry and declared characteristics describe a battery model and are shared by every unit of it. State of health describes one physical battery, changes continuously as that battery is used, and only exists after the battery has been in service.
It is derived rather than directly observed. A battery management system computes it from measurements such as capacity fade, internal resistance, cycle count and operating conditions, which means the value depends on the method used to derive it. Two systems can report different figures for the same physical battery without either being wrong in its own terms, which is why the method matters as much as the number.
Its practical importance is in second life and end of life. Whether a battery is worth repurposing, what it can be sold for, and how it should be treated all depend on its condition rather than on its original specification. Publishing it to parties with a legitimate interest, such as repairers, remanufacturers, second-life operators and recyclers, is what allows those decisions to be made without dismantling the battery first.
Why It Matters
State of health is the clearest example of passport information that does not exist at the point of manufacture. A design that assumes all passport content is known before the product ships cannot carry it. Supporting it requires deciding how field data is collected, how often it is refreshed, how much history is retained, and who is entitled to see it.
Relationship to Digital Product Passports
The general passport concept distinguishes product data from lifecycle event data. State of health sits firmly in the second group, alongside usage data and status. It is the reason a battery passport is an operated service rather than a published document.
Common Misconceptions
State of charge is how full the battery is right now. State of health is how much capability it has left compared with when it was new. A fully charged battery can have poor state of health.
It is derived from measurements using a method, and the method affects the result. The parameters and their determination are addressed by Article 14 and Annex VII of Regulation (EU) 2023/1542 for the batteries in scope.
Related Terms
Related Knowledge Base Articles
- Digital Product Passports for Batteries: What Companies Need to Know
- What Data Goes in a Digital Product Passport, and Where Does It Come From?
Related Articles
- Battery Passport
- Authorised Representative
- Authoritative Source
- Circular Economy
- Conformity Assessment
- Corrective Action
- Data Architecture
- Data Carrier
See Also
References
- Regulation (EU) 2023/1542 concerning batteries and waste batteries: https://eur-lex.europa.eu/eli/reg/2023/1542/oj
About This Article
tieback Knowledge is a continuously maintained reference library covering Digital Product Passports, product traceability, product compliance and related regulations. Articles are reviewed regularly as legislation, standards and implementation guidance evolve.