{"id":13085,"date":"2021-11-08T00:06:03","date_gmt":"2021-11-08T05:06:03","guid":{"rendered":"https:\/\/autosector.com\/auto\/?p=13085"},"modified":"2021-11-08T00:06:03","modified_gmt":"2021-11-08T05:06:03","slug":"tesla-liion-12v-auxiliary-battery","status":"publish","type":"post","link":"http:\/\/autosector.com\/?p=13085","title":{"rendered":"Tesla’s New 12V Li-Ion Auxiliary Battery Has CATL Cells Inside"},"content":{"rendered":"

With the refreshed<\/a> Model S<\/a>\/Model X<\/a>, Tesla<\/a>\u00a0switched from conventional lead-acid to an all-new lithium-ion 12 V auxiliary battery<\/strong> (Model 3\/Model Y still uses a conventional one).<\/p>\n

Thanks to an outstanding, two-part presentation and teardown conducted by Ingineerix,<\/em> we can take an in-depth look at this new solution, hinted at in early 2021 by Elon Musk<\/a> and shown only briefly at the delivery event<\/a>.<\/p>\n

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.<\/p>\n

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 (like here<\/a>).<\/p>\n

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.<\/p>\n

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).<\/p>\n

According to Ingineerix<\/em>, such batteries last in Teslas about 2-4 years, which is pretty low and sometimes causes unexpected problems if the car stops working.<\/p>\n

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\"Tesla <\/picture>\n

Tesla 12 V conventional lead acid battery (source: Ingineerix)<\/p>\n<\/section>\n

\"Tesla <\/picture>\n

Tesla 12 V conventional lead acid and lithium battery (source: Ingineerix)<\/p>\n<\/section>\n<\/section>\n

The new,lithium-ion battery is much smaller and much lighter (only about 4 lbs \/ 1.8 kg). That’s because it’s much higher energy density, but also has a lower energy content. We assume that with a more reliable and “smart” solution, there is no need for 0.4 kWh.<\/p>\n

The battery has only a 0.1 kWh of energy (99 Wh to be precise) and a capacity of 6.9 Ah, according to the description.<\/p>\n

The nominal voltage is slightly higher than normally in lead-acid battery (12.8 V). With four cells in series (3.7 V nominal) it should be at 14.8 V for most of the time.<\/p>\n

\"Tesla <\/picture>\n

Tesla Model S Plaid 12 V lithium battery (source: Ingineerix)<\/p>\n<\/section>\n

As we can see in the second video (on the bottom of this post), the new battery consists of a BMS circuit board made by CATL<\/a> and four prismatic NMC lithium-ion battery cells (6.9 Ah each), connected in series.<\/p>\n

It means that not only are the entry-level Model 3\/Model Y equipped with CATL batteries (LFP traction batteries), but also the all-new flagship Model S\/Model X has CATL batteries (just the auxiliary, not traction ones).<\/p>\n

There are no signs of a heating system for the battery, which indicates that it’s not required. According to the general CATL specs, the battery cells can accept charging at temperatures as low as -10\u00b0C. And they can discharge at temperatures as lows as -20\u00b0C.<\/p>\n

There is a theory that the system can heat up the battery with a repeated slow charging\/discharging if needed.<\/p>\n

The cycle life appears to be high at over 2,000 cycles until the capacity will decrease to 80% of the initial value. If everything was well designed, it should last as long as the car.<\/p>\n

\"Tesla <\/picture>\n

Tesla Model S Plaid 12 V lithium battery with CATL NMC cells (source: Ingineerix)<\/p>\n<\/section>\n

Tesla Model S Plaid lithium-ion 12 V auxiliary battery:<\/strong><\/p>\n

    \n
  • 6.9 Ah minimum (7.5 Ah maximum)<\/li>\n
  • 99 Wh<\/li>\n
  • four cells in series\u00a0(1P4S)<\/li>\n
  • lithium-ion NMC prismatic cells manufactured by CATL<\/li>\n
  • Cell specs (according to CATL’s general spec for 6.9 Ah cells):
    NMC chemistry
    6.9 Ah
    3.7 V nominal (4.2 V max charge voltage, 2.75 V minimum)
    charging temperatures: from -10\u00b0C to +45\u00b0C
    discharging temperatures: from -20\u00b0C to +60\u00b0C
    max charging: 10C
    max peak discharging: 50C
    cycle life: >2,000 cycles (80% of initial capacity at 3C rate)<\/li>\n<\/ul>\n
    \"\"\/ <\/p>\n