EV High-Voltage Safety Handbook for Workshops

The 8-Step Lockout/Tagout (LOTO) Procedure

This is the single most important procedure in EV safety. Always follow all steps in order. Never skip steps to save time.

Step 1: Prepare & Communicate

• Inform all personnel in the area that HV work is about to begin
• Ensure only authorized, trained personnel are in the work area
• Gather all required PPE and tools before starting
• Review the vehicle-specific service manual — every manufacturer has different procedures

Step 2: Power Down the Vehicle

• Turn vehicle ignition OFF
• Remove key fob from vehicle (keep at least 5m away — many cars can "wake up" if fob is near)
• Disconnect 12V battery (negative terminal first, then positive)
• Wait 2-3 minutes for all HV capacitors to discharge (check manual for exact time)

Step 3: Put On PPE

• Put on flame-resistant clothing if not already wearing
• Put on face shield
• Put on insulated gloves (with leather protectors)
• Verify all PPE is in good condition
• Stand on insulated mat if available

Step 4: Locate Service Disconnect

• Consult service manual for exact location
• Common locations: under rear seat, in trunk, under hood, on battery pack itself
• Orange = HV. The service disconnect plug is always orange

Step 5: Disconnect Service Plug

• Grasp the plug by the insulated handle only
• Pull straight out — do not twist or yank
• Inspect plug for damage or corrosion
• Keep the plug with you — this is your "key" — nobody can re-energize without it

Step 6: Apply Lockout/Tagout

• Install your personal lock on the service disconnect housing
• Attach warning tag with your name and date
• You hold the only key — nobody else can remove the lock
• If multiple people are working, each person applies their own lock

Step 7: Verify Zero Energy State

• Most critical step! Always test before touching
• Use a calibrated HV multimeter to verify zero voltage on both sides of the disconnect
• Test the meter on a known live source first (to confirm meter works)
• Then test the circuit (should read 0V)
• Then test the meter again on known live source (to confirm it still works)
• This is called "live-dead-live" testing

Step 8: Proceed With Work

• Now you can safely work on HV components
• Keep all tools and parts organized
• Never leave the work area unattended while HV components are exposed
• When finished, reverse the procedure to re-energize

REMEMBER: If at any point you're unsure or something doesn't feel right — stop. Consult the service manual or a senior technician.

Battery Fire Risks

Lithium-ion battery fires are different from regular fires. They can self-ignite, burn at extreme temperatures, release toxic fumes, and reignite hours or days later. Understanding the unique dangers is essential.

Thermal Runaway Stages

1. Stage 1 - Onset: Cell overheats, electrolyte begins to break down. Venting gas may be visible. Smell of sweet/sour chemicals.
2. Stage 2 - Escalation: Temperature rises rapidly. Cell vents flammable gases. Swelling and hissing sounds.
3. Stage 3 - Thermal Runaway: Fire starts, temperature exceeds 700°C. Chain reaction spreads to adjacent cells.
4. Stage 4 - Post-Fire: Battery may appear "out" but can reignite from residual heat. Cells can remain dangerous for days.

Early Warning Signs

• Unusual smells (sweet, chemical, or burning plastic)
• Smoke or vapor from the battery area
• Swelling or bulging of the battery pack
• Hissing or popping sounds
• Vehicle displaying battery overheating warnings
• Rapid battery percentage drop when parked

If you see ANY of these signs: Evacuate the area immediately. Move the vehicle outside if it's safe to do so (only if you can drive it without entering the passenger compartment). Call emergency services.

Battery Fire Response Procedure

1. EVACUATE IMMEDIATELY — Get all people away from the vehicle and building (minimum 15m distance)
2. CALL EMERGENCY SERVICES — Tell them it's an electric vehicle battery fire
3. DO NOT attempt to put out a battery fire with a standard fire extinguisher — it won't work and you'll waste time
4. DO NOT open the battery pack or try to access the cells
5. If safe and available: Flood the battery area with large volumes of water (fire hose). Water doesn't put out Li-ion fires, but it cools the cells and can slow thermal runaway spread. This requires fire department equipment — not a workshop extinguisher.
6. Best approach for workshops: If a battery catches fire, move the vehicle outside (if safe to drive), let it burn in a controlled area, and call the fire department. Your building and people are more important than the car.

Damaged Battery Storage

• Any battery that has been in a crash, punctured, or damaged in any way is a fire risk
• Store damaged batteries outside, away from buildings and other vehicles
• Use a dedicated fire-resistant battery storage container if available
• Never store damaged batteries indoors or near flammable materials
• Label clearly: "DAMAGED HV BATTERY — FIRE RISK"
• Dispose of through certified hazardous waste handlers only

Workshop Layout Requirements

Dedicated HV Work Zone

• Clearly marked with warning tape and signs
• Restricted access — only trained personnel allowed
• Non-slip insulated flooring or rubber mats
• Minimum 3m clearance around vehicle work area
• Good ventilation — especially for battery work
• Fire-resistant walls/ceilings if budget allows

Safety Equipment Checklist for HV Workshop

Equipment	Quantity	Location
Class D fire extinguisher	2 minimum	HV zone exit, battery storage
Fire blanket (large)	1	HV zone entrance
First aid kit with burn kit	1+	Near HV zone
Emergency eyewash station	1	HV zone (within 10m)
Smoke detectors	Per zone	Ceiling, battery storage
Thermal imaging camera	1 recommended	For battery temperature checks
Warning signs & labels	As needed	All entrances and HV components

Training Requirements

All Workshop Staff (Level 1 — Awareness)

• Understand the dangers of high voltage
• Know which parts of an EV are HV (orange cables and components)
• Know never to touch orange components
• Know emergency procedures
• Duration: 4-8 hours

EV Service Technicians (Level 2 — Qualified Person)

• All Level 1 content
• Lockout/tagout procedures
• PPE selection, use, and inspection
• HV system decommissioning and verification
• Hands-on practice with various vehicle models
• First aid & CPR certification
• Duration: 40-80 hours (5-10 days)

Battery Specialists (Level 3 — Expert)

• All Level 2 content
• Battery pack disassembly and reassembly
• Cell-level safety procedures
• Thermal runaway response
• Battery testing and diagnostics
• Hazardous materials handling
• Duration: 80-160 hours (2-4 weeks + mentorship)

Final Safety Checklist — Before Every HV Job

• ☐ Job briefing completed with all involved personnel
• ☐ Service manual reviewed for specific vehicle
• ☐ All required PPE present and inspected
• ☐ Work area clear of non-essential personnel and hazards
• ☐ Fire safety equipment accessible
• ☐ Vehicle properly immobilized (park, chocks, etc.)
• ☐ Key fob removed from area
• ☐ 12V battery disconnected
• ☐ HV system decommissioned per procedure
• ☐ Zero-energy verified with calibrated meter (live-dead-live)
• ☐ Lockout/tagout applied

Your safety is more important than any job. If something doesn't feel right — stop. Ask. Verify.