Setyr worked example — BP-2 EV Battery Pack Line — Module Station Isolation Not approved for use. Version 1 · 2026-09-25
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
BP-2 EV Battery Pack Line — Module Station Isolation
EV battery
Maintenance at a module stacking and busbar welding station on an EV battery pack line. Covers the packs themselves, which arrive charged and cannot be de-energised, alongside the laser welder, station power and the gas detection that stays live.
This is a worked example, not a procedure you can adopt. It describes equipment that does not exist, with illustrative tag numbers.
29 CFR 1910.147(c)(4) requires the employer to develop, document and
utilise energy control procedures specific to their own machines, and (c)(6)
requires the employer to inspect those procedures periodically. Neither duty
can be delegated to a vendor or discharged by this document.
Isolation points
| # | Tag (illustrative) | Type | Disposition | What it does and why | Dwell |
|---|---|---|---|---|---|
| 10 | BP-2-MOD-HV | Bleed | CANNOT BE ISOLATED | Battery modules present at the station. Nominal 400V pack, cells arrive at partial state of charge. Caution: A charged lithium module has no off switch. There is no disconnect, no bleed, and no state in which it is safe to short. Removing it from the work area is the only control. Modules CANNOT be isolated. Remove all modules from the station and place them in the quarantine rack before work begins, or treat the station as live. | — |
| 20 | BP-2-MSD | Disconnect | Isolate & lock | Manual service disconnect on any partially assembled pack remaining at the station. Caution: Removing the MSD splits the pack but does not discharge the halves. Each half remains at hazardous voltage. Remove the MSD, retain it under personal control, and allow the pack capacitors to discharge before touching busbars. | 300s |
| 30 | BP-2-STN-ISO | Disconnect | Isolate & lock | Station 480V main disconnect feeding the stacker, welder and conveyor. Caution: Station isolation does nothing to the energy stored in the modules on the line. Open, lock, prove dead at the load side. | — |
| 40 | BP-2-LASER | Breaker | Isolate & lock | Laser welder supply and beam shutter interlock. Caution: A class 4 beam is invisible and reflects off busbar. Interlocks are defeated for setup more often than anyone records. Open and lock the welder supply. Confirm the beam shutter is closed and the key is under personal control. | — |
| 50 | BP-2-CAP | Bleed | Isolate & lock | Welder capacitor bank in the laser power supply cabinet. Caution: The grounding hook is applied after the meter reading, not instead of it. Allow the capacitor bank to discharge for the full time, then confirm below threshold with a meter and apply the grounding hook. | 600s |
| 60 | BP-2-ROBOT | Disconnect | Isolate & lock | Module handling robot servo power at the station. Caution: Servo brakes fail to applied, but a robot holding a module overhead is relying on those brakes. Open and lock servo power. Confirm the robot brakes hold with power removed. | — |
| 70 | BP-2-ROB-BLK | Block | Apply & verify | Mechanical arrest pin on the robot axis carrying load over the station. Caution: Brake failure with a module in the gripper drops it into the work area. The pin is the backup. Insert the axis arrest pin. Must be ENGAGED. | — |
| 80 | BP-2-AIR | Valve | Isolate & lock | Station pneumatic supply to clamps, lifts and the pack fixture. Caution: Clamps release on loss of air on this fixture, which drops the pack rather than holding it. Bleed only with the pack removed. Close and lock the supply, then bleed the station air header to zero. | 90s |
| 90 | BP-2-COOL | Valve | Isolate & lock | Glycol coolant fill and leak-test connection to the pack cooling plate. Caution: Coolant onto exposed busbar creates a conductive path across cells that cannot be switched off. Close and lock both fill and return valves. | — |
| 100 | BP-2-EXH | Breaker | KEEP ENERGISED | Station fume extraction over the weld area. Caution: Welding fume and, in a thermal event, vented electrolyte both leave through this system. Do NOT isolate. Confirm extraction is running. | — |
| 110 | BP-2-GAS | Breaker | KEEP ENERGISED | Electrolyte vapour and hydrogen detection at the station and over the quarantine rack. Caution: A module in thermal runaway vents before it burns. Detection is the warning that lets people leave. Do NOT isolate. Confirm detection is in service before work begins. | — |
| 120 | BP-2-SUPP | Valve | KEEP ENERGISED | Station fire suppression sized for a lithium event, and the quarantine rack immersion bin. Caution: A lithium fire is not put out by a standard extinguisher. The bin is the plan. Do NOT isolate. Confirm suppression is in service and the immersion bin is filled and accessible. | — |
What your site must supply
- Your own asset and isolation-point tag numbers. The tags shown are illustrative and refer to equipment that does not exist.
- The actual location of every disconnect, valve and vent on your equipment.
- Measured stored-energy magnitudes and the dwell time required to dissipate them.
- Your verification method for each point, and who is authorised to perform it.
- Any additional energy sources present on your equipment and absent here.
Authorship and validation
This example was authored by Setyr for domain validation. It is not derived from any customer's controlled documents. It illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain — it does not certify compliance, which is a property of an employer's programme rather than of any document.