Fire Detection for Battery Energy Storage and Solar PV
Battery energy storage systems and solar photovoltaic arrays are arriving in buildings that were never designed around them — plant rooms, basements, rooftops and dedicated enclosures. They bring risks a conventional fire alarm was not built to address: thermal runaway in lithium batteries, DC electrical hazards, and fires that can behave and evolve differently from those the building's detection was arranged for. This guide covers why these installations deserve specific thought, and what to check.
The central point is that a general fire alarm cannot be assumed to cover a battery or PV installation; its risks need to be considered on their own terms.
Who this is for
This is for competent fire alarm engineers encountering battery energy storage or solar PV within or alongside the systems they maintain. The experience level assumed is competent engineer. Use it for the principles; the specific detection and interface arrangements come from the fire risk assessment, the manufacturer's requirements and any specialist guidance, coordinated with BS 5839-1. Some aspects are specialist and sit beyond the fire alarm engineer's remit.
A newer kind of risk
Battery energy storage and solar PV introduce hazards that a building's fire alarm was not originally designed around. Lithium battery storage carries the risk of thermal runaway, which can develop heat and flammable or toxic gases quickly and spread between cells; solar PV adds DC electrical risk that persists while there is light. Because these differ from the ordinary fire the detection was arranged for, they should be considered specifically rather than assumed to be covered. How detection and any interface are arranged comes from the fire risk assessment, the manufacturer's requirements and BS 5839-1 where the building's system is involved.
Understanding thermal runaway
Thermal runaway is worth understanding because it shapes how detection is thought about. It is a self-sustaining rise in a cell's temperature that can propagate to neighbouring cells and release gases before, or differently from, a conventional flaming fire. This is why detection appropriate to the technology — which the manufacturer or risk assessment may specify as gas detection or very early smoke detection such as aspirating — is often considered for these installations. The point is not that the building smoke detector is useless, but that it may not give the early, technology-appropriate warning these systems need. The specific approach follows the manufacturer's guidance and the fire risk assessment.
How detection is arranged
In practice, detection for these installations is a design question answered outside the general fire alarm. The building's BS 5839-1 system protects the building for life safety; a battery or PV installation may need its own detection or a dedicated arrangement suited to its risk, with any interface to the building system — such as raising an alarm or triggering a cause and effect — defined deliberately. From field experience, the recurring problem is an installation dropped into a plant room or enclosure with no review of whether the existing detection suits it, and no defined interface at all. Whether and how they connect comes from the fire risk assessment and the manufacturer's requirements, coordinated with BS 5839-1.
Servicing around these installations
When servicing a building that now contains battery storage or PV, treat it as something to check rather than ignore. Confirm any detection serving the installation is present, appropriate and working; that interfaces to the building fire alarm behave per the documented cause and effect; and that changes to the installation have been reflected in the fire risk assessment. From field experience, detection not suited to the technology and installations added with no review at all are the common findings. Record what you find, and flag anything beyond your competence — the battery or PV system itself — for specialist assessment rather than guessing.
Common points to check
Recurring issues include a battery or PV installation added with no review of detection, detection present but not appropriate to the technology, and interfaces to the building fire alarm that are undefined or untested. Confirming the installation has been assessed and any interface proven is the essential check.
When not to rely on this alone
When not to use this article: do not treat it as design guidance for battery or PV fire protection, which is specialist and technology-specific. Those decisions come from the fire risk assessment, the manufacturer's requirements and specialist guidance, applied by competent professionals in the relevant field.
Relevant standards
Where the building's fire alarm is involved, it follows BS 5839-1, a code of practice, within the fire risk assessment; the protection of the battery or PV installation itself follows the manufacturer's requirements and any specialist guidance. The legal duty to manage fire risk in most non-domestic premises sits under the Regulatory Reform (Fire Safety) Order 2005, with Building Regulations statutory guidance in Approved Document B applying to building work. Separate the legal duty from the recommended methods, and always work to current editions.
Professional disclaimer
This is an educational and workflow resource for competent engineers and does not replace the current British Standards, the manufacturer's requirements, the fire risk assessment, or competent judgement. Battery and PV fire protection is a specialist matter; verify arrangements against current documentation and specialist advice.
Related documentation
Use this with the current BS 5839-1, the fire risk assessment, and the manufacturer's requirements for any battery or PV installation. Record detection and interfaces serving these installations, and flag any added or altered without assessment for specialist review.