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Tesla's New 12V Li-Ion Auxiliary Battery Has CATL Cells Inside
With the refreshed Model S/Model X, Tesla switched from conventional lead-acid to an all-new lithium-ion 12 V auxiliary battery (Model 3/Model Y still uses a conventional one).
Thanks to an outstanding, two-part presentation and teardown conducted by Ingineerix, we can take an in-depth look at this new solution, hinted at in early 2021 by Elon Musk and shown only briefly at the delivery event.
The video starts with a general overview of why EVs still use 12 V auxiliary batteries and why they continue to use lead-acid ones, while the main traction battery is lithium-ion.
The lead-acid batteries turned out to be problematic in EVs, due to a different use case than a starter battery and manufacturers are expected to switch to lithium-ion versions sooner or later (partially, with the potential transition to 48 V auxiliary systems). Some individual users were already replacing their 12 V batteries with a li-ion version on their own
In general, a lithium-ion battery should be smaller, lighter, more reliable and last longer. It could be a bit more expensive, but the total cost of ownership should be lower.
The old lead-acid battery vs new lithium-ion
As we can see in the video, previously Tesla was using in the Model S/Model X a 12 V, 33 Ah lead-acid AGM battery. It stores about 0.4 kWh of energy, but weight is quite substantial: 27 lbs (12 kg).
Tesla 12 V conventional lead acid battery (source: Ingineerix)
Tesla 12 V conventional lead acid and lithium battery (source: Ingineerix)
