Electrical Precautions


Avoid getting grease on electrical components and connectors. Grease collects dirt, which can cause electrical tracking (short circuits) or high resistance.

Handle printed circuit boards (PCBs) at an electrostatic discharge (ESD) work station only. Hold printed circuit boards by the edges only.

Warning: ESD wrist straps should never be worn when working with High Voltage (HV) components.


Warning: The vehicle has low voltage (12V) and High Voltage (HV) (400V) circuits. To fully disconnect the HV system, refer to Service Manual procedure 17010000, "Vehicle Electrical Isolation Procedure."
Warning: Only technicians who have been trained in High Voltage Awareness are permitted to perform this procedure. Proper personal protective equipment (PPE) and insulating HV gloves with a minimum rating of class 0 (500V) must be worn any time a high voltage cable is handled. Refer to Tech Note TN-15-92-003, "High Voltage Awareness Care Points" for additional safety information.
Warning: Makes sure that multimeters and leads are capable of handling at least 500V before performing a procedure that involves high voltage.
Warning: Never disconnect or cut an orange high voltage power cable or HV component unless the HV system has been disabled.
Warning: After disabling the vehicle, power is maintained for 30 seconds in the Supplemental Restraint System (SRS) and 1 minute in the high voltage electrical system.
Warning: Never cut into the HV battery enclosure.

HV Battery and HV Circuits

The HV battery stores all of the energy for the motor and vehicle electrical systems. The HV circuits can sense a variety of conditions that could potentially damage the vehicle or pose a safety risk. Their primary response in these circumstances is to disconnect the HV from the rest of the vehicle.

When the HV battery is not in a vehicle, high voltage is not accessible without removing the penthouse cover.

Warning: Remove all jewelry (watches, bracelets, rings, necklaces, earrings, ID tags, piercings, etc.) from your person, and all objects (keys, coins, pens, pencils, tools, fasteners, etc.) from your pockets before performing any procedure that exposes you to high voltage.
Warning: If corrective eyewear is necessary to safely perform any procedure, make sure that the eyewear is securely restrained to the head and cannot fall off.
Warning: An HV battery poses a significant high voltage and electrocution risk if the outer enclosure or safety circuits have been compromised or have been significantly damaged.
Warning: Always remove the HV battery before performing any procedure that might require using a drill near the HV battery, especially drilling downward from inside the vehicle.
Warning: If the HV battery or vehicle displays signs of escaping gases, smoke, flames, excessive heat, sparks, or arcing, contact the local emergency department and refer to the applicable Emergency Response Guide, available at https://www.tesla.com/firstresponders. Gases or smoke exiting a lithium-ion HV battery are likely flammable and could ignite at any time.

12V Battery

The 12V battery used in Model 3 is similar to the lead acid batteries used in most internal combustion engine vehicles. Lead acid batteries are sometimes referred to as "flooded" because they are filled (flooded) with sulfuric acid.

Warning: Lead acid batteries contain an electrolyte with dilute sulfuric acid, which can cause severe chemical burns if it comes in contact with skin.
Warning: Lead acid batteries can emit hydrogen and oxygen, which can result in an explosion under certain conditions. Only charge the 12V battery in a well-ventilated area that is free from sparks or open flame.
Warning: Keep the 12V battery upright at all times. The 12V battery is vented (not sealed), allowing the sulfuric acid to spill out if the battery is not kept upright.
Warning: Use only battery chargers specified by Tesla. Charging the battery outside of the recommended specification can cause the battery to overheat and increase the possibility that acid and hydrogen gas will be released, possibly causing personal injury, damage to the vehicle, fire, or an explosion.
Warning: Batteries can be a source of high electrical current and can cause an electrical shock in certain situations, such as a short circuit.
Warning: To avoid personal injury, use proper lifting techniques when handling the 12V battery.
Warning: To prevent vented gases from entering the cabin intake or corroding components, always makes sure the 12V battery ventilation tube is reinstalled after performing work.
The HV battery in Model 3 will support a damaged/over discharged 12V battery whether or not the vehicle is being driven. However, upon detection of 12V battery degradation, the vehicle provides alerts indicating that the 12V battery needs replacement. If these alerts are ignored for a considerable period of time, the HV battery can become discharged to the point of no longer supporting the 12V battery (and the vehicle will have to be jump-started), or the 12V battery may become overheated due to nearly continuous charging.

Over discharging a 12V battery can cause permanent damage to the battery and increase the likelihood of overheating during charging. If a vehicle has an over discharged or "dead" 12V battery, always replace the 12V battery. Even if an over discharged battery is charged again successfully, the damage incurred is likely to cause future reliability problems.

Prevent unnecessary 12V battery replacement. If a vehicle is unable to support the 12V battery, or has a low HV State of Charge and is unable to be recharged, disconnect 12V power (refer to Service Manual procedure 17010200). Keeping the 12V battery connected might result in damaging the 12V battery through over-discharge.
Note: An overheated 12V battery can begin to leak acid from the vent hose, begin to smell of “rotten eggs,” and may become swollen.
Table 1. State of 12V Battery
12V Battery Condition Open Circuit Voltage
Good >12.6 V
Needs Recharge Between 12.4V to 12.6V
Replace <12.4V

Electrical Connectors and Harnesses

  • Never pull on a wiring harness to disconnect an electrical connector.

  • Never use tools to force connectors apart.

  • Ensure that disconnected connectors and sensors are protected from oil, coolant, water, or other contaminants.

  • Ensure that electrical items are dry and free of oil or grease before disconnecting and connecting test equipment.

  • After reconnecting an electrical connector, lightly pull on it to make sure that it is secured.

  • When replacing a component, keep oily hands away from electrical connection areas.

  • Make sure that any protection (cover, insulation, etc.) is replaced, if disturbed.

Grease for Electrical Connectors

Some underhood and underbody connectors might be protected against corrosion by the application of a special grease during vehicle assembly. Apply the appropriate grease when repairing or replacing these connectors. Do not use other greases. Incorrect greases can migrate into relays, switches, etc. contaminating the contacts and leading to intermittent operation or failure.

Do not apply grease to any connectors that do not have grease applied from the factory.

First Aid Measures

Seek immediate medical assistance if an electrical shock or electrocution has occurred or is suspected.

Under normal conditions, technicians are not exposed to the contents of the HV battery cells. If materials from a ruptured or otherwise damaged battery contact skin, flush immediately with water and wash the affected area with soap and water. Avoid inhaling any vented gases. If a chemical burn occurs, or if irritation persists, seek medical assistance. For eye contact, flush with significant amounts of water for 15 minutes and see a physician immediately.

Warning: An HV battery poses a significant high voltage and electrocution risk if the outer enclosure or safety circuits have been compromised or have been significantly damaged.
Warning: Avoid contact with gases escaping from a damaged battery. Vented gases might irritate the eyes, skin, and throat. Vent gas temperatures can exceed 600 ºC (1,110 ºF). Contact with hot gases can cause burns.

HV Battery Storage Precautions

  • Do not store HV batteries below -20 ºC (-4 ºF).

  • Do not store HV batteries for over 10 days above 35 ºC (95 ºF).

  • Do not charge or discharge a HV battery below 0 ºC (32 ºF).

  • Do not store HV batteries for over 30 days at full State of Charge (SOC), or completely discharged.

  • Do not cut, drill, or weld near HV batteries.

Install plugs in each HV connection before storing the HV battery.

Note: If plugs for the HV connectors are not available, cover the connector(s) with 3M 2480S masking tape or 3M 471 vinyl tape.

HV batteries should be stored in a dry area, in approved packaging, or on non-conductive surfaces. To reduce the risk of accidental shorting, make sure that there is no loose metal or other conductive materials near stored batteries.

HV batteries should not be stored longer than 9 months since HV battery service life likely will be affected. If longer storage is anticipated, contact Tesla for instructions.

HV Battery Disposal Procedures

The lithium-ion cells contained in the HV battery do not contain heavy metals such as lead, cadmium, or mercury.

HV batteries should be disposed of or recycled in accordance with local, state, and federal regulations. Regulations regarding disposal of HV batteries vary by jurisdiction. In the United States, batteries are classified as Universal Waste, and in addition, many individual states have specific regulations regarding disposal of HV batteries.

HV batteries contain recyclable materials. Tesla strongly encourages recycling. Tesla recommends that all HV batteries be taken to a Tesla Service Center so that the batteries can be evaluated, and, if appropriate, be recycled in a safe and efficient manner.

If disposing of an HV battery without returning it to Tesla, consult with local, state and /or federal authorities on the appropriate methods for disposal and recycling.