Plug-in van and truck grant: preparing battery degradation evidence
Updated 24 November 2023
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The battery degradation requirement can be met in one of 3 ways, which are:
a) warranty terms that explicitly cover the battery against unreasonable degradation
b) actual data from tests undertaken on an appropriate sample of batteries. Data shows they have not degraded unreasonably after a period of 3 or more years in service
c) written assurance from the applicant that the battery will offer a reasonable performance, comparable with or better than the rates of degradation specified. The applicant must provide evidence to support their assurance
Assessing evidence
In cases where the applicant is seeking approval via option c, the evidence provided may be in the form of:
- illustrative evidence of the degradation rate under certain conditions, such as under an accelerated testing regime
- a supporting explanation of the way in which this evidence demonstrates long-term maintenance of the performance
The Vehicle Certification Agency (VCA) may consider the elements listed below as indicators of quality sufficient to offer reasonable performance during normal use.
In this context, it will consider what is appropriate to the vehicle and the range or performance stated by the manufacturer.
The applicant may wish to identify the possible failure modes and the mitigating actions that have been taken.
As a guide to the level of detail expected, we would not expect the evidence submitted to require more than 10 pages. Annexes can be provided if desired.
The VCA or supporting independent technical experts may request additional information to inform assessment of the application.
What will be assessed
The factors which the VCA and independent technical experts will take into account when assessing the evidence are:
Battery cell
Data at the cell level can include the published test data of cell manufacturers.
Transportation
Conforms to UN transport standard ST/SG/AC.10/11/Rev.7.
Cycling tests
Provide appropriate evidence, to represent the final application of:
- c-rating
- depth of discharge
- influence of temperature on characteristics
Self discharge rates
Values and method of establishing them.
Impedance
Measurement method and evolution with both elapsed time and use.
Capacity
Measurement method and evolution with both elapsed time and use.
Battery pack
Evidence needs to clearly show how the cells have been combined to produce performance in a battery pack that meets the stated specification.
Mechanical integrity
- resistance to stresses caused by dimensional changes of cells in operation
- what vibration, strength and damage testing has been performed?
- strategy for preventing and containing effects of cell failures
Thermal integrity
Provide a summary of your thermal management strategy and how it is achieved, such as cell-to-cell temperature variation and overall pack temperature control.
Cycling tests
- are the tests appropriate to the claimed usage of the vehicle?
- are the cycling profiles, ratings and temperatures of the tests appropriate?
Environmental resistance
- what is the ingress protection (IP rating) of the pack?
- resistance to dusts and liquid and gaseous contaminants
- resistance to extremes of temperature
Battery management system
How does the battery management system (BMS) ensure that the individual cells are not required to operate outside of its specification?
Vehicle
The integration of a battery pack into the operational context of a vehicle can impact on the battery degradation rate. How has this been considered by the manufacturer?
In addition to the points below, the issues considered at the pack level should also be addressed at the vehicle level.
Battery Management System
How does the BMS ensure that the battery pack is not required to operate outside of its specification?
Thermal integrity
What cooling strategy has been put in place to support the operation of the battery in the UK environment?
Onboard diagnostics
- what error and information messages will be provided to the rider on the status of the battery?
- what error messages will be recorded for maintenance?
Dirt, dust and water ingress, and mechanical stress
What measures have been taken to assess and control these factors?
Fire performance
Is there a report that confirms appropriate testing has been carried out?
To note: similar guidance will be supplied on preparing fuel cell degradation evidence as more fuel cell vehicles come to market.