Tesla Self-Activated Draining System

The Tesla Self-Activated Draining System was patented some time ago, but this simple mechanical device is still being used in the latest Cybertruck.

A method of managing leakage of liquid inside a battery system comprises: containing leaking liquid in a non-liquid sensitive region of the battery system so as to protect internal electrical components of the battery system from coming in contact with the leaking liquid; and in direct response to the leakage, expunging the leaking liquid from the battery system.

Tesla Self-activated draining system

A drain device includes:

  • a body with a port therethrough
  • the body configured to be positioned in a wall of a container
  • means for opening the port in response to a first liquid contacting the drain device on an inside of the container
  • means for resisting ingress into the container by a second liquid that contacts the drain device on an outside of the container.

This post has been built based on the support and sponsorship from: Thermo Fisher ScientificEatron TechnologiesAbout:Energy and Quarto Technical Services.

Tesla self activating drain plug

The actual part from a 2023 Cybertruck [2].

Munro Live show the part and a breakdown with the expanding discs.

There also appears to be other designs of this mechainism used by Tesla.

Coolant liquid leaking into the battery enclosure can result in failure or thermal runaway of the pack. There are a number of ways in which companies approach this problem. The VW ID4 has the liquid coolant system attached to the underside of the battery enclosure.

In many forums you will see people asking what they should do if they see coolant leaking from the battery pack, this is probably due to the Tesla Self-Activated Draining System working and releasing fluid from a failed coolant system. This is a serious fault and the dealer should be contacted immediately.


  1. Self-activated draining system, US9293792B2
  2. Tesla Cybertruck Battery Pack: Our First Impressions Under the Lid, Munro Live, YouTube
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