Tesla Model 3 12V Lithium Battery Replacement Kit – Lightweight

Description

Did you know that the factory 12V battery in your Telsa Model 3 is a heavy, inferior AGM battery? Somewhat silly that a car with up to 75kWh worth of lithium batteries has a heavy, old technology like AGM as the low voltage battery! But this is understandable since the added cost just didn’t make sense for Tesla with the Model 3. Our 12V Lightweight Lithium Battery Replacement Kit for Tesla Model 3 shaves 24 pounds from the front of the chassis. At MPP we’re hyper-focused on weight reduction, so to be able to get 24 lbs out in quick 30 minute bolt in part is massive.

Testing the 12V Lithium Tesla Battery Replacement Kit for Model 3

We’ve been quietly testing our lithium 12V battery since June 2018, installing it almost directly after receiving our car. We knew that we needed to perform heaps of real-world testing before offering our battery kit – as we needed to ensure the vehicle’s normal behavior continued – such as regularly falling into deep-sleep, performing OTA software updates normally, waking up quickly for mobile access, and having no issue in the extreme cold.

Unfortunately, as of December 2022, the extreme cold does cause some issues with the vehicle detecting the 12V battery is weak (even when it isn’t). See below for more details. We do not recommend this battery for those who store their cars in temperatures below 45 degrees F.

Of course, we also performed a significant amount of safety and suitability testing with our battery kit – ensuring the Model 3’s DCDC always charged at an acceptable current and voltage for this battery’s chemistry. We’re happy to report that this battery is a perfect match for the Model 3’s DCDC charge logic. We are happy to discuss details with those of you that are concerned about this.

December 2022 Update: While the Tesla DCDC charges the battery at the optimal voltage and the battery continues to work well, Tesla seems to have made their “12V battery testing” routine more sensitive, and this battery can fail that test if the battery is cold. When this test fails, the car will report that the 12V battery needs to be replaced, and will turn off power to noncritical 12V systems, thinking the battery is bad when it really isn’t. The good news is that this error can be cleared relatively easily, but the bad news is that it will reoccur if you store your vehicle in a cold location, such as outdoors or in an unheated garage (below 40 degrees F or so).

Technology

One thing that was extremely important to us when selecting a battery was to use one that has a built-in BMS (battery management system) that is capable of disconnecting the battery from the vehicle in the event of a fault. We selected the EarthX ETX900 because has both under and over-voltage protection, as well as cell management. This means in the event that the battery is drained below a safe voltage, the BMS will disconnect the battery from the vehicle so that the voltage does not continue to fall to a level that would otherwise damage the battery.  The built-in BMS also balances the voltages of the individual cells connected in series, so that the battery never has a single cell that goes above a dangerously high voltage – something that most other aftermarket lithium-ion batteries do NOT have, making them potentially dangerous for long term operation.

The 12V Lithium Battery we selected to put in the Model 3 is the EarthX ETX900 – designed and manufactured in the USA, and is normally used to power small aircraft! So you can take comfort in knowing that if it is safe enough for flight it’s safe and reliable enough for your Model 3. The battery can deliver a massive 840 cranking amps (not that our Tesla’s will need that!)

Installation

Of course, we wanted to make an extremely light, easy-to-install and elegant battery bracket to go along with the battery. That was no easy task considering the smaller size of our battery and the strange stamped bracket on the Model 3. There was no way we were going to make a bracket that weighed almost as much as the battery, so a lot of design went into a CNC machined, 6061 aluminum bracket that bolts into the OEM battery carrier with no drilling or cutting required. We also decided to use a strap rather than an aluminum bracket to further reduce weight, and we include all stainless steel hardware so that rust and corrosion will never be an issue! Fortunately, the result is that the 12V Lithium Tesla Battery is easy to install!

Installation Instructions HERE

How to reset 12V battery calibration HERE