Tesla Model 3 Owners & Service Manuals

Tesla Model 3: 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.

Caution:

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.

Caution:

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.

Caution: 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.

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