SWECO BUILDING STANDARDS GUIDANCE NOTE
Charging Lithium-Ion Batteries: Safety Guidance
Published on: 05/04/2024
The emerging risk of fires starting from charging of lithium-ion batteries is of concern particularly as no formal guidance is provided in Approved Document B. However, the guidance states that Building Control Bodies and Design Teams should establish if the guidance is appropriate, and it has been explicitly established through the Grenfell Enquiry that guidance being “silent” does not necessarily indicate compliance.
This guidance note gives advice on recognition and mitigation of the issues presented to enable surveyors to encourage design teams to consider the risk. The design team should be clear that they are ultimately responsible for the compliance of their design.
The scope of the note includes, batteries taking charge from renewables, recharging of mobility scooters and electric wheelchairs, and recharging of electric bikes and scooters. This note does not cover electrical vehicle charging. This is covered in our Guidance Note 5 and the Office for Zero Emission Vehicles (OZEV) T0194 – Covered car parks – fire safety guidance for electric vehicles.
Consideration needs to be made of the building’s use, size and complexity of design and construction.
Where possible in the common parts of flats or buildings having the purpose group “other than dwellings” the space in which charging takes place should be treated as a ‘place of special fire hazard’. It should meet the guidance given in terms of fire resistance and separation as a minimum. However, the design team should be encouraged to consider if additional mitigation would be beneficial, and the client should be clear of the ongoing residual risk they will need to manage.
There are several options that can be used in to help mitigate the risk presented by lithium-ion battery charging, they include:
- Place the battery in an appropriately located fire compartment with access for maintenance and repair.
- Environmentally controlled environments, to prevent overheating of the space.
- Fire Detection.
- Fire Suppression.
- Provide battery thermal management devices that automatically cut charging if issues detected.
Guidance
Recharging of electric bikes and scooters in commercial properties
The risk should be recognised during the design process and the client involved in deciding how they wish to control the risk. There are two key factors to consider:
1. What management provisions will be in place?
a. Safety testing of batteries brought into building?
b. Active management of the E bike/scooter policy that the building design is based on?
2. Where will the E bikes/scooters (batteries) be stored and allowed to recharge? Ideally this would be in a carefully positioned, dedicated fire compartment with appropriate passive and active fire precautions.
3. If possible, the storage area should have alternate means of escape. If the storage area only has a single route of exit, the charging positions should be remote and consideration given to appropriate maximum travel distances.
Recharging of electric bikes and scooters in residential properties
Sweco does not think this risk can be practically managed through the Building Regulations. The risk should be recognised during the design process and the client involved in deciding how they wish to control the risk. Depending on the nature of the building, the Responsible Person may be able to impose various conditions on the occupants to control the risk.
Insurance Risk
It should be noted that the insurance risk may lead to a more onerous solution than in this guidance.
Batteries taking charge from renewables
It is increasingly common now to install lithium-ion batteries with residential PV installations. Given the structural and fire precaution issues presented by the installation of these systems, this work is material and controlled under the Building Regulations.
It is our view that where possible all the above mitigation should be provided. The compartment should ideally be entered from external air, the entry point should not prejudice a final exit or result in the risk of a breakout fire playing over window openings. Where this is not possible the compartment should be placed as remote from internal circulation/escape routes as possible. The fire resistance should be a minimum of 30 minutes. Ultimately the design team should substantiate the fire resistance chosen based on the risk.
Batteries taking charge from renewables
It is our view that placing a battery in the traditional truss, cold deck residential roof space is inappropriate as:
- The cold deck roof spaces are not environmentally controlled and the increases in temperature that occur on hot days are inappropriate for lithium-Ion batteries.
- It is completely impractical to provide fire resistance from the roof space down.
- Occupants would be unaware that a fire had started and potentially the roof space could be used for storage significantly increasing the fire load. Conventional residential Automatic Fire Detection (AFD) is not designed to withstand the typical temperature differences experienced in a residential roof space.
Since this guidance note was first issued, detailed guidance on the installation of residential batteries taking charge from renewables has been published in PAS 63100:2024
Recharging of mobility scooters and electric wheelchairs
Ideally charging for these modes of transport should be in a separate fire compartment that is not contained in common parts or within the residence itself. The fire resistance should be based on the level of risk the compartment presents. The risk would be determined through consideration of the size and anticipated number of charging stations within the compartment and the inclusion or not of the other mitigation features listed above.
Both the current and draft BS 9991 give guidance that this form of risk in communal areas should be facilitated in separate “compartments” with 30-minute fire separation.
The design team should consider if this simple approach meets the risk presented, and how it would meet the access requirements of the individual.
Allowance needs to be made in the design of these compartments for accessibility including:
- The numbers of residents that could utilise the space; and
- Adequate transfer spaces adjacent to the storage positions.
If it is proposed to place the charging point within the residence, meeting the functional requirements of Parts B and M need to be considered. The design should demonstrate how the integrity of the escape route is maintained to the flat entrance door. Special consideration should be given from the sleeping accommodation whilst at the same time achieving the needs of the wheelchair user given in Part M.
Maintaining the means of escape and placing the wheelchair storage/transfer/charging space in the ideal location from an access point of view presents a conflict that perhaps can only be overcome by putting the space in a fire-resistant compartment. However, compartmenting (physically enclosing) the minimum sized space given in Part M would lead to transfer and accessibility issues. Consequently, the design team would need to consider any additional space needed to maintain its accessibility. Also, thought would need to be given for environmental controls, to prevent the build-up of heat. Finally, the need within the space for fire detection, suppression, thermal management and power cut off devices should be considered.
It is recognised that often the design team will struggle to meet the above and may decide to use the provision of safety information to occupants as the best solution. The content of this information is the responsibility of the design team in the first instance and then that of the Responsible Person. From a Building Control perspective, prior to issuing a completion certificate, confirmation should be recorded that the client has received and accepted the information.
The contents of this Guidance Note are confidential to Sweco and the intended recipient and are subject to copyright in favour of Sweco. The content of this Guidance Note must not be reproduced by any person (including the intended recipient) without the prior written consent of Sweco.
The Guidance Note does not constitute professional advice and Sweco hereby offers no reliance and accepts no liability (in contract, tort (including negligence) or otherwise) for parties acting on the content of this Guidance Note without taking specific professional advice from Sweco. The Guidance Note is provided as generic guidance only and any opinion, views or advice expressed in this Guidance Note are made without any representations or provide any assurances or warranties as to the content. If you require specific advice with respect to your own project or circumstances, please contact Neil Badley.