Guidance

Plug-in motorcycle grant: preparing battery degradation evidence

Updated 6 April 2024

The applicant must demonstrate that the battery or fuel cell used to drive the motorcycle propulsion system has a reasonable rate of degradation.

As a guide to applicants, pending the evidence presented in each case, a reasonable level of degradation is defined as:

• for battery electric models, the battery must maintain at least 80% of its initial or rated charge capacity for the initial 3 years, or 70% of initial capacity for the initial 5 years
• for fuel cell vehicles, the fuel stack must maintain at least 90% of its rated voltage output for the initial 5 years.

Given the novelty of fuel cell technology, we are prepared to work with manufacturers to supply alternative evidence that provides what the panel judges to be a reasonable level of reassurance to the consumer.

This criterion is intended to:

• provide a minimum level of reassurance to the market
• support the second-hand market
• preserve the presentational integrity of the market against claims of low-quality product

The scope of the evidence requested is intended to allow the applicant flexibility so that they can show their battery or fuel cell degradation rate in a manner suitable to their own development processes.

We recognise the challenges around providing the technical evidence for this criterion:

• the fact that different battery or fuel cell manufacturers will have developed their own quality assurance tests and procedures
• the proprietary nature of some of the data produced by these tests and procedures
• the difficulty of providing long-term ‘real world’ test data on products that may be new to the market

Technical evidence may be assessed in confidence either by the internal panel or by independent technical experts.

Assessing test data evidence

If providing reasonable performance evidence in the form of test data, the applicant should describe the range of tests performed on the battery.

Any evidence presented should be supported by a statement of:

• the published or proprietary standard that the tests were performed in accordance with
• confirmation that the testing laboratory operates in accordance with an internationally recognised accreditation regime

Assessing written assurance evidence

In cases where the applicant is seeking approval via written assurance of reasonable performance, 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.

This must be together with 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 following elements 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 range/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 may be provided if desired.

The assessment panel and/or supporting independent technical experts may request additional information to inform assessment of the application.

What will be assessed: written assurance

The types of indicators or factors that the panel and independent technical experts will take into account when assessing this 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.

What cooling strategy has been put in place to support the operation of the battery in the UK environment?

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 the battery degradation rate. How has this been considered by the manufacturer?

The issues considered at the pack level should be addressed at the vehicle level in addition to the following:

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.