High Voltage Safety

Step 1 — Look up the manufacturer-specific de-energization procedure for this exact vehicle make, model, and year before you do anything else. Procedures vary significantly between manufacturers. Tesla is different from Rivian is different from Ford is different from Hyundai. Never assume one procedure applies to all vehicles.

Step 2 — Put on Class 0 or Class 00 insulated rubber gloves rated for the HV system voltage. Inspect them visually and perform an air inflation test before every use — squeeze the cuff shut and roll from the cuff toward the fingers to inflate the glove. Look and feel for any air leaks, cracks, punctures, or thin spots. Wear leather protector gloves over the rubber gloves to prevent punctures during work. Safety glasses on. Remove all metal jewelry — rings, watches, bracelets, necklaces — before putting on gloves. Metal creates a conductive path.

Step 3 — Disable the vehicle. Turn ignition off, remove the key or fob. For push-button start vehicles, place the fob in a shielded pouch away from the vehicle so it cannot inadvertently wake the system. Set the parking brake.

Step 4 — Disconnect the 12V auxiliary battery negative cable. This prevents control modules from commanding HV contactors closed.

Step 5 — Locate and remove the HV service disconnect plug or manual service disconnect. Location varies — under the rear seat, in the trunk, under the cargo floor, or under the hood depending on the vehicle. Find the location in manufacturer service information before starting. Some disconnects are plugs you pull. Some are handles you turn. Some require a tool. All should be done with insulated gloves on.

Step 6 — Wait the manufacturer's specified capacitor discharge time. Typically 5 to 10 minutes. The high-voltage capacitors inside the inverter retain a lethal charge after the disconnect is removed. The capacitors must discharge through internal bleed resistors before the system is safe. Do not skip or shorten this wait under any circumstances. Use the time productively — review the rest of the service procedure.

Step 7 — Use a CAT III rated digital multimeter capable of reading at least 1000 volts DC. Verify zero voltage at the HV service disconnect terminals. Confirm zero voltage at any HV access points specified by the manufacturer. You must read zero with your own meter before touching any HV component. If you read any voltage at all — stop. Something is wrong. Re-verify your entire disconnect procedure.

If an EV is involved in a collision or fire, do not spray water directly into the battery pack area unless trained to do so. Battery fires can produce toxic fluoride gas. Damaged HV cables may be exposed. Emergency response guides for each vehicle are available from the manufacturer — most fire departments carry them. As a technician, if a damaged EV arrives on a flatbed, do not touch it until you have assessed the HV system status and verified it is safe.