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Why Tesla’s lead acid 12V battery needs to be lithium-ion based

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It’s a prominent issue surrounding the electric vehicle market that the old-school lead acid battery just isn’t appropriate for new technology vehicles. Many users of electric vehicles, especially Tesla owners, have cited concerns with the poor performance of their 12V or low-voltage battery, oftentimes requiring annual replacement.

In contrast, a lead acid battery in a traditional internal combustion engine (ICE) vehicle generally has a 4 year life-cycle, but why?

RELATED: Tesla Model S 12V Lithium-Ion battery replacement (up to 70% lighter, 4x life)

First off, some of the most important factors to consider in longevity of a battery are “cycle-life”, environmental conditions, discharge/charge rates and calendar-life; cycle-life is how many times the battery can be drained and recharged in its life. Environmental conditions include temperature and humidity. Discharge/charge rates are the amperages going out of and into the battery respectively.

There are two major differences between the way an ICE vehicle uses its 12V battery and the way an EV uses its 12V battery:

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“OFF” state discharge and cycling frequency

ICE Vehicle: generally has a very low 12V load while the vehicle is in the “off” state, often this load doesn’t exceed a few watts and doesn’t present a major challenge for the 12V battery to maintain.

Electric Vehicle: The 12V load while in the off-state is often much higher due to advanced computer systems that are running to maintain the high-voltage battery, keep vehicle “connected” (all EV have some remote access features), maintain charging and BMS (Battery Management System) communications, etc. In fact a Tesla Model S/X puts about 50 Watts of load on the 12V system when the vehicle is in the “off” state. 50 Watts equals about 4.5 Amps of discharge on the 12V battery, this drains the battery down relatively rapidly and requires the 12V battery be “recharged” by the high-voltage battery regularly, this usage pattern results in many cycles being placed on the battery.

“ON” state utilization and purpose

ICE Vehicle: The 12V battery is used to initiate the ICE (start the car) and is designed for putting out large amounts of current to accommodate this process.  Once an ICE vehicle is in the “on” state, it relies on an alternator to power all of the 12V sub-systems and also maintain the voltage of the 12V battery.

Electric Vehicle: The 12V is subjected to (practically) no additional load while the vehicle is being turned “on”, and although most vehicles are designed with DC/DC converters (which act as alternators) it is often an engineering design choice to reduce load on the DC/DC converter by minimizing the frequency with which it is utilized. This also extends the driving range of the vehicle because none of the precious high-voltage battery capacity is being shunted to non-driving tasks. Due to this usage profile the 12V battery is subjected to relatively low discharge and recharge currents.

When you combine the high number of cycles and the low current requirements of the electric vehicle 12V battery system you arrive at a completely different battery need than that of an ICE vehicle.  Lead Acid batteries are very good at high discharge and low cycle count life-styles, this is their bread and butter and this is where they last a long time and provide the most bang for the buck (cheap cost and decent product life-cycle), but they aren’t lasting in electric vehicles.

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The electric vehicle 12V battery system is one that is best suited by a battery capable of tremendous cycle-life as the main design goal. The battery chemistry that suits this usage scenario best?  Lithium! Lithium battery technology is specifically very good at being cycled many times and continuing to provide minimal capacity loss and degradation. This, along with reduced weight, is why these batteries are used for the high-voltage battery packs, cell-phones, laptops, medical equipment and cars where batteries are being cycled frequently and longevity is important.

Editor’s note: This post was submitted into our network by Tesla Model S owner Sean Scherer. Having suffered an unfortunate incident in his Model S that left him stranded because of a faulty 12V battery, Sherer began on a mission to create a lithium-ion based 12V battery solution that was not only more reliable than the traditional lead acid battery, but better suited for the demands of a Tesla Model S, Model X, and electric vehicles in general. He began BattMobile Batteries, who have made it their mission to improve adoption of electric vehicles by solving some of the small details that has been missed by EV manufacturers.

We’ve also included a video tutorial on how to replace the Model S 12V battery.

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Tesla owners propose interesting theory about Apple CarPlay and EV tax credit

“100%. It’s needed for sales because for many prospective buyers, CarPlay is a nonnegotiable must-have. If they knew how good the Tesla UI is, they wouldn’t think they need CarPlay,” one owner said.

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Credit: Tesla Raj/YouTube

Tesla is reportedly bracing for the integration of Apple’s well-known iOS automotive platform, CarPlay, into its vehicles after the company had avoided it for years.

However, now that it’s here, owners are more than clear that they do not want it, and they have their theories about why it’s on its way. Some believe it might have to do with the EV tax credit, or rather, the loss of it.

Owners are more interested in why Tesla is doing this now, especially considering that so many have been outspoken about the fact that they would not use it in favor of the company’s user interface (UI), which is extremely well done.

After Bloomberg reported that Tesla was working on Apple CarPlay integration, the reactions immediately started pouring in. From my perspective, having used both Apple CarPlay in two previous vehicles and going to Tesla’s in-house UI in my Model Y, both platforms definitely have their advantages.

However, Tesla’s UI just works with its vehicles, as it is intuitive and well-engineered for its cars specifically. Apple CarPlay was always good, but it was buggy at times, which could be attributed to the vehicle and not the software, and not as user-friendly, but that is subjective.

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Nevertheless, upon the release of Bloomberg’s report, people immediately challenged the need for it:

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Some fans proposed an interesting point: What if Tesla is using CarPlay as a counter to losing the $7,500 EV tax credit? Perhaps it is an interesting way to attract customers who have not owned a Tesla before but are more interested in having a vehicle equipped with CarPlay?

“100%. It’s needed for sales because for many prospective buyers, CarPlay is a nonnegotiable must-have. If they knew how good the Tesla UI is, they wouldn’t think they need CarPlay,” one owner said.

Tesla has made a handful of moves to attract people to its cars after losing the tax credit. This could be a small but potentially mighty strategy that will pull some carbuyers to Tesla, especially now that the Apple CarPlay box is checked.

@teslarati :rotating_light: This is why you need to use off-peak rates at Tesla Superchargers! #tesla #evcharging #fyp ♬ Blue Moon – Muspace Lofi

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Investor's Corner

Ron Baron states Tesla and SpaceX are lifetime investments

Baron, one of Tesla’s longest-standing bulls, reiterated that his personal stake in the company remains fully intact even as volatility pressures the broader market.

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Credit: @TeslaLarry/X

Billionaire investor Ron Baron says he isn’t touching a single share of his personal Tesla holdings despite the recent selloff in the tech sector. Baron, one of Tesla’s longest-standing bulls, reiterated that his personal stake in the company remains fully intact even as volatility pressures the broader market.

Baron doubles down on Tesla

Speaking on CNBC’s Squawk Box, Baron stated that he is largely unfazed by the market downturn, describing his approach during the selloff as simply “looking” for opportunities. He emphasized that Tesla remains the centerpiece of his long-term strategy, recalling that although Baron Funds once sold 30% of its Tesla position due to client pressure, he personally refused to trim any of his personal holdings.

“We sold 30% for clients. I did not sell personally a single share,” he said. Baron’s exposure highlighted this stance, stating that roughly 40% of his personal net worth is invested in Tesla alone. The legendary investor stated that he has already made about $8 billion from Tesla from an investment of $400 million when he started, and believes that figure could rise fivefold over the next decade as the company scales its technology, manufacturing, and autonomy roadmap.

A lifelong investment

Baron’s commitment extends beyond Tesla. He stated that he also holds about 25% of his personal wealth in SpaceX and another 35% in Baron mutual funds, creating a highly concentrated portfolio built around Elon Musk–led companies. During the interview, Baron revisited a decades-old promise he made to his fund’s board when he sought approval to invest in publicly traded companies.

“I told the board, ‘If you let me invest a certain amount of money, then I will promise that I won’t sell any of my stock. I will be the last person out of the stock,’” he said. “I will not sell a single share of my shares until my clients sold 100% of their shares. … And I don’t expect to sell in my lifetime Tesla or SpaceX.”

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Watch Ron Baron’s CNBC interview below.

@teslarati :rotating_light: This is why you need to use off-peak rates at Tesla Superchargers! #tesla #evcharging #fyp ♬ Blue Moon – Muspace Lofi
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Tesla CEO Elon Musk responds to Waymo’s 2,500-fleet milestone

While Tesla’s Robotaxi network is not yet on Waymo’s scale, Elon Musk has announced a number of aggressive targets for the service.

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Credit: Tesla

Elon Musk reacted sharply to Waymo’s latest milestone after the autonomous driving company revealed its fleet had grown to 2,500 robotaxis across five major U.S. regions. 

As per Musk, the milestone is notable, but the numbers could still be improved.

“Rookie numbers”

Waymo disclosed that its current robotaxi fleet includes 1,000 vehicles in the San Francisco Bay Area, 700 in Los Angeles, 500 in Phoenix, 200 in Austin, and 100 in Atlanta, bringing the total to 2,500 units. 

When industry watcher Sawyer Merritt shared the numbers on X, Musk replied with a two-word jab: “Rookie numbers,” he wrote in a post on X, highlighting Tesla’s intention to challenge and overtake Waymo’s scale with its own Robotaxi fleet.

While Tesla’s Robotaxi network is not yet on Waymo’s scale, Elon Musk has announced a number of aggressive targets for the service. During the third quarter earnings call, he confirmed that the company expects to remove safety drivers from large parts of Austin by year-end, marking the biggest operational step forward for Tesla’s autonomous program to date.

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Tesla targets major Robotaxi expansions

Tesla’s Robotaxi pilot remains in its early phases, but Musk recently revealed that major deployments are coming soon. During his appearance on the All-In podcast, Musk said Tesla is pushing to scale its autonomous fleet to 1,000 cars in the Bay Area and 500 cars in Austin by the end of the year.

“We’re scaling up the number of cars to, what happens if you have a thousand cars? Probably we’ll have a thousand cars or more in the Bay Area by the end of this year, probably 500 or more in the greater Austin area,” Musk said.

With just two months left in Q4 2025, Tesla’s autonomous driving teams will face a compressed timeline to hit those targets. Musk, however, has maintained that Robotaxi growth is central to Tesla’s valuation and long-term competitiveness.

@teslarati :rotating_light: This is why you need to use off-peak rates at Tesla Superchargers! #tesla #evcharging #fyp ♬ Blue Moon – Muspace Lofi
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