Battery system fire risk during commissioning

This highlights the fire hazards and control measures during the commissioning phase of Battery Energy Storage System (BESS) projects.

Commissioning involves energising electrical systems for the first time, one of the most critical and high-risk stages in the project lifecycle.

BESS commissioning introduces live energy sources and potential ignition points.

Lithium-ion cells can enter thermal runaway when damaged, overcharged or poorly ventilated.

Such events can escalate rapidly and result in serious fires, explosions or environmental releases.

Recent UK incidents demonstrate that commissioning remains one of the highest-risk phases for BESS fire events.

In September 2020 at Carnegie Road, Liverpool, a fire occurred in a BESS container during commissioning.

In July 2023 at Northwich, Cheshire, a thermal event occurred inside a lithium battery cabinet during commissioning; the suppression system contained it.

In February 2025 in Aberdeen, Scotland, a thermal runaway event was initiated after units were found to be faulty during delivery, coupled with issues with installation of the fire suppressant.

In February 2025 in Thurrock, Essex, a fire led to thermal runaway within a single containerised BESS unit.

Systems may be energised before full Battery Management System (BMS) validation.

Cable terminations may be loose or incorrect.

Protective relays may be bypassed or alarms disabled.

Cells may be charged at a high state of charge (SOC), above 30%.

Combustible materials, including packaging and solvents, may remain in live zones.

Fire watch arrangements or communication during tests may be inadequate.

Before commissioning:

• Complete a pre-energisation inspection of connections, torque and insulation.
• Verify that fire detection and suppression systems are functional.
• Maintain the state of charge below 30%, or the manufacturer-specified limit, unless authorised by the Engineering Manager.
• Confirm fire alarm integration and emergency plan readiness.
• Complete pre-commissioning sign-off or a permit to energise.

During commissioning:

• Assign a fire watch with direct communications to the control room.
• Restrict access to authorised personnel only.
• Keep monitoring telemetry and temperature feeds active.
• Stop work immediately if heat, smell or smoke is detected.

After commissioning tests:

• Allow adequate cooling and trend temperature stability.
• Record all alarms, trips or unusual readings.
• Conduct a debrief and Toolbox review for lessons learned.

Emergency actions:

• If there is a fire, raise the alarm, shout “FIRE”, activate the nearest alarm point and call 999 (or your local emergency number).
• Evacuate to the designated muster point.
• Do not attempt to re-enter the site once evacuated unless authorised.
• Do not attempt to open containers or panels.
• Notify the Commissioning Manager and Site Controller immediately.
• Only trained responders should engage, as lithium-ion fires can reignite.

Key learnings from industry examples:

• Early-stage testing is high risk. Ensure correct isolations, suppression systems and monitoring systems are active before energisation.
• Confirm gas detection and BMS integrity before initiating testing sequences.
• Ensure thorough delivery checks of all equipment are undertaken.
• Have a robust procedure in place for separating any damaged equipment.
• Ensure contractor competence is thoroughly checked.
• Maintain close liaison with the local fire and rescue service.
• Have water attenuation complete before BESS equipment arrives at site.
• Use a robust design process to ensure adequate spacing is achieved ahead of construction.

• How can something like this happen here, for example on our site?
• What safety measures, procedures, controls or barriers do we have in place to mitigate the fire risk during commissioning?
• How do we know that fire detection, suppression, monitoring and alarm controls are working before energisation?
• How do we identify, isolate and manage damaged or faulty battery equipment before commissioning starts?
• What improvements should we make to commissioning procedures, emergency arrangements or the way we work?