Tesla, Inc. has published a new patent for identifying a presence of a short circuit in a battery pack. This fault-detection apparatus would accumulate data while a system is actively charging, monitor the results against anomalous conditions, and compare those conditions against a set of predetermined profiles that seem to produce internal shorts in one or more cells of the collection. Six authors from California are cited as collaborative inventors for the patent.

Identifying short circuits in a Tesla battery pack could be instrumental in preventing consumer safety incidents. The Tesla community was concerned in 2015 when a Tesla Model S was hit by lightning while charging and a Model S fire erupted in Norway in 2016, although causal effects of short circuits in those battery packs are uncertain.

Tesla patent

Why is it important to identify the presence of a short circuit in a battery pack?

When a battery pack short circuits, it can reduce overall performance capability and even cause hazardous conditions. Shorts can be caused by a number of reasons, including manufacturing/ design defects, poor cell design, or electrochemical abuse. Many lithium-ion batteries have been recalled due to manufacturing defects, and subsequent manufacturing-quality control improvements have reduced their failure rate significantly. Because it is important to determine situations that might cause excessive heat generation or over-discharge, for example, Tesla has filed a patent for identifying the presence of cell shorts, particularly during charging.

The average EV battery cell packs use thousands of individual battery cells clustered in interconnected modules or bricks in ways that produce sustained high-energy storage and output. This environment, however, makes it difficult to gather and evaluate specific and accurate individual cell information.

Brief summary of the invention

Identifying a presence of a short circuit in a collection of interconnected battery cells, according to the new patent, would mean working through a series of steps to:

  • receive a set of data parameters while actively charging
  • evaluate that data to cull out any anomalies
  • compare those anomalies against against a set of predetermined profiles typical of an internal short in one or more cells of the collection
  • establish an internal-short state when a data relationship among profiles emerges.

Conditions for data collection

The invention offers several ways to identify when a cell is behaving abnormally and may have an internal-cell short. Some of the anomalous conditions that might occur include a change in cell impedance over time, an increase in total charge passed, or change in temperature. Each of these could be signs of internal-cell shorts.

For relevant data to emerge, monitoring would rely on a frequent and likely continuous series of  data acquisition, measurement, and evaluation. Conditions for monitoring can be subtle, depending on different contexts such as driving, charging, and parking.

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