In brief
In battery module and pack assembly, cells always hold energy; the classic "isolate the energy, then work" approach is therefore not enough on its own. Safe production is built on four headings: terminal protection and insulated tools against the voltage that rises as series connections increase, quarantine and an emergency plan against thermal runaway in damaged modules, suitable lifting equipment for heavy modules and packs, and high-voltage work being done only by authorised employees.
Battery production safety: why is a new risk assessment needed?
An automotive supplier moving from internal combustion engine parts to electric vehicle components starts with parts such as battery housings, cooling plates, busbars and cable harnesses; the next step may be module and pack assembly. Dies, welding and the assembly line are familiar; what is unfamiliar is that the product itself is an energy source. This is why battery production safety needs to be treated as a separate heading.
For this reason, adding a few rows to the existing risk assessment is not enough. The Regulation on Risk Assessment requires the assessment to be renewed regardless of its period when technology, substances or equipment change and when the production method changes. The hazards of the new line fall under four headings:
| Hazard | Source | Main consequence |
|---|---|---|
| Electrical | Direct current voltage created by cells connected in series | Electric shock, arcing and burns |
| Thermal runaway | A damaged, crushed, punctured or short-circuited cell | Fire, explosion, toxic gas |
| Mechanical and ergonomic | Heavy modules and packs, tight assembly clearances | Crushing, falling loads, back and shoulder strain |
| Chemical | Electrolyte leaks, combustion and decomposition products | Respiratory and skin exposure |
We explained how to manage the change process in our article on change management and risk revision. This article focuses on the measures specific to the battery line.
High-voltage vehicle assembly: a cell cannot be switched off
In the automotive industry, the term "high voltage" is used differently from its meaning in the power grid. UNECE Regulation No. 100 on electric vehicle safety treats direct current circuits above 60 V and alternating current circuits above 30 V as high voltage. The pack voltage of a vehicle battery is far above this value.
The real problem on the assembly line is this: the voltage of a single cell is low, but as cells are connected in series, the voltage rises from station to station. It is not possible to isolate the energy by switching off a breaker as you would on a machine; a cell carries energy from the moment it is produced. For this reason, the logic of lockout and tagout is applied differently on a battery line:
- Draw up a voltage map. Determine the voltage at the exposed terminals at each station on the line. Which stations count as high-voltage work is decided on the basis of this map.
- Keep terminals covered until the last moment. Terminals not yet connected to a busbar are protected with insulating caps; a cap is removed only at the moment the connection is made.
- Fix the connection sequence. Series connections are made in the order given in the work instruction; a busbar connected in the wrong order can create a short circuit and arc.
- Use the service disconnect. If the pack has a disconnect that splits the voltage, it is removed before testing and repair, and the absence of voltage is verified by measurement.
- Authorised employees only. People who will work at high-voltage stations are authorised in writing after training and a practical assessment; the list is posted at the station.
For the general principles of electrical work, see our article on the five safety rules in electrical work, and for the vocational competence of people doing electrical work, who can do electrical work.
Insulated hand tools and choosing PPE
When tightening a busbar bolt, a spanner touching two terminals at once is enough to cause an arc and burns. For this reason, wrapping tape around an ordinary tool is not a measure at high-voltage stations.
- Insulated hand tools: Hand tools suitable for live working are manufactured to TS EN IEC 60900 and marked for use up to 1000 V AC and 1500 V DC. The tool must carry the mark of conformity to the standard, and there must be no cracks or cuts in the insulating layer. A defective insulated tool is not repaired; it is replaced.
- Torque tools: The correct torque on busbar connections matters for both product quality and the risk of heating and arcing. Torque tools must also be insulated.
- Electrical insulating gloves: Classified under TS EN 60903; the class is chosen according to the working voltage. Before each use, an air test is done to check for holes, and leather protector gloves are worn over them against mechanical damage.
- Face and body protection: Where there is an arc risk, an arc-rated face shield and suitable clothing are used. Rings, watches and metal jewellery are removed.
- Work surface: An insulating bench cover or floor mat reduces the effect of accidental contact.
PPE is the last barrier. First, measures such as terminal caps, the connection sequence and authorisation are put in place; PPE is chosen on top of these.
Thermal runaway and managing damaged modules
Thermal runaway is when heating that starts inside a cell feeds itself and rises rapidly. It can start when a cell is crushed, punctured, dropped or overcharged, or when an internal short circuit occurs; it can spread to neighbouring cells, and flammable and toxic gases are released. These gases may include irritant and toxic substances such as hydrogen fluoride.
For battery module safety, the following arrangement should be set up on the line:
- Definition of damage: A module that is dropped, takes an impact, swells, heats up, or gives off a smell or smoke is considered "damaged" and taken off the line.
- Quarantine area: Damaged modules are kept separate from the main production area, in a section cleared of combustible material, outdoors if possible or fire-resistant, in a suitable medium such as a metal container or sand.
- Monitoring: The temperature and condition of a quarantined module are checked at set intervals; records are kept.
- Emergency plan: The method for responding to a battery fire, the evacuation distance and the actions to take against the gas risk are put in writing together with the manufacturer's safety information and the fire brigade. For facilities within an OIZ (organised industrial zone), see our article on emergency coordination with the OIZ fire brigade for this coordination.
In an electrolyte leak, the area is ventilated without contact and cleaned up according to the instructions in the safety data sheet. If chemical exposure in the workplace needs to be measured, we plan the measurement with authorised laboratories. For measures specific to charging and formation areas, see our article on lithium battery charging area safety.
Handling heavy modules and packs
Modules can weigh tens of kilograms, and finished packs hundreds. These weights cannot be carried by hand, and dropping them in transit carries both a crushing risk and a thermal runaway risk.
- Lifting equipment: Modules and packs are lifted with grippers designed specifically for the product. The surfaces of the grippers in contact with the product should be insulating and must not touch the terminals.
- Periodic inspection: Cranes, manipulators and vacuum or mechanical lifting accessories are inspected by competent persons at least once a year unless the standard specifies a shorter interval. We plan and track the schedule of these inspections; the inspection itself is carried out by competent persons registered on EKİPNET (the Ministry's register of persons authorised for periodic inspections).
- Manual tasks: For tasks such as feeding cells and small modules, weight and the number of repetitions are assessed together; for the method, see our article on how many kilos can be lifted (NIOSH).
- Working under packs: Nobody goes under a suspended pack; underside connections are not made until the pack is secured on the assembly stand.
The test area and electric vehicle servicing
End-of-line tests include insulation and voltage tests; the test area should be separated so that unauthorised people cannot enter during testing, and there should be an audible or visual warning system. The connecting leads and probes of test equipment are also subject to the rules for insulated equipment.
The same principles apply in electric vehicle servicing and repair workshops. The vehicle manufacturer's instructions for disabling the high-voltage system are followed step by step, any waiting time is observed, and the absence of voltage is verified by measurement. When working on the vehicle, a high-voltage warning sign is placed and the area is cordoned off with tape. For other risks in workshops, see our article on OHS in car repair workshops. Shipments of cells, modules and packs are subject to the rules on the carriage of dangerous goods; for whether an adviser is required, see our article on who needs a dangerous goods safety adviser (TMGD).
Checklist for the battery line
| Stage | Check |
|---|---|
| Cell receipt and storage | Is damaged packaging separated; is the store separate and monitored from a fire perspective? |
| Module assembly | Terminal caps, connection sequence, use of insulated tools |
| Pack assembly | Voltage map, list of authorised employees, high-voltage warnings |
| Lifting | Product-specific gripper, periodic inspection report, no working under suspended loads |
| Damaged product | Definition of damage, quarantine area, monitoring record |
| Testing | Separated area, warning system, test instruction |
| Emergencies | Battery fire scenario, evacuation distance, fire brigade coordination |
| Training | High voltage, thermal runaway and damaged product covered in job-specific training |
In automotive supply industry businesses in Bursa and the surrounding provinces, at the set-up stage of electric vehicle component lines we work with you to put the voltage map, quarantine arrangements and authorisation system in place through our risk assessment and OHS specialist services. You can track the inspection dates of lifting equipment with the OHS calendar.
Frequently Asked Questions
Does battery module assembly count as electrical work?
At stations where the voltage rises through series connection, work done with exposed terminals is high-voltage work and requires separate training and authorisation. The line's voltage map determines which stations fall within this scope.
What is the difference between an insulated hand tool and an ordinary tool?
Insulated hand tools are manufactured and tested to TS EN IEC 60900 as suitable for live working. Tape or a sleeve wrapped around an ordinary tool's handle does not provide the same protection.
Where is a damaged battery module kept?
In a quarantine area separated from the main production area, cleared of combustible material and, if possible, outdoors or fire-resistant. The module's condition is checked at set intervals and recorded.
Are extra measures needed for employees in electric vehicle servicing?
Yes. The vehicle manufacturer's instructions for disabling the high-voltage system are applied, the absence of voltage is verified by measurement, insulated tools and suitable PPE are used, and only trained, authorised employees do this work.
A risk assessment that identifies and scores hazards on site, links each measure to an owner and a date, and has a clear renewal schedule.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.