Isn’t the Model 3, or any Tesla for that matter, a massive battery in itself? And if it is, what’s the need for a 12V battery?
If such questions are crossing your mind, you’re in the right place.
The quick answer is that even though EVs themselves are massive batteries, there are many processes (powering lights, etc.) necessary for the proper running of the car that require a 12V battery.
After going through forums, Tesla manuals, and several YouTube videos, I’ve compiled this quick guide that’ll teach you all about the Tesla Model 3 12V battery and what functions it performs.
We’ll also go through some common problems related to the 12V battery that owners faced and what they did to get rid of them.
If that sounds compelling, read on.
Does the Tesla Model 3 Have a 12V Battery – And Where Is It?
Like all other models of Tesla (Y, S, X), the Model 3 also comes up with a 12V battery. All you have to do is pop up the frunk, and there you’ll have access to it.
At this point, most new owners will ask, “Why does Tesla require a 12V Battery even though it itself is a massive battery?”
Here is how power gets distributed in your Tesla Model 3:
Tesla Main Battery:
- Provides powertrain
- Provides energy for air conditioner and cabin heater
- DC-DC charging of 12V battery
Tesla 12V Secondary Battery:
- Powers lights, media unit, windows, locks, etc.
- Provides energy backup when the main battery starts dying! If the primary battery fails while you’re driving, this 12V battery supplies enough power for the car to safely steer and brake to a safe spot
Current (and Older) Tesla Model 3 12V Battery Specs Comparison
Before we delve into the comparison, it’s important to note that the chemistry of Tesla’s 12V batteries seemingly changed from lead-acid to lithium-ion on the Model 3/Y recently.
With that aside, let’s do a side-by-side comparison of both batteries from different perspectives:
Cost
To begin with, lead-acid batteries are significantly less expensive than lithium-ion batteries in the short term, but over the length of the battery’s life span, lithium-ion batteries look like a more feasible option.
Weight
When it comes to electric vehicles, shaving weight is necessary as it directly relates to car efficiency.
Now if we compare both batteries side by side in terms of weight, the lead-acid battery is insanely heavy. A lead-acid battery weighs approximately 325+ pounds, while a lithium-ion battery weighs around 75 pounds.
And since it’s lightweight, the lithium-ion battery certainly increases your car’s efficiency by three to four times, which certainly is a big deal.
Maintenance Overview
Lithium-ion batteries are literally maintenance-free; yes, they don’t require maintenance at all.
However, lead-acid batteries are an absolute bummer. They require frequent maintenance in terms of:
- Watering (you have to keep optimum water levels)
- Corrosion cleanup (check if they are clean so the charge terminals don’t get corroded after some time)
- Monitoring the discharge limits (keep a check that they don’t fall by the 50% charge limit)
Well, it’s a hell of a lot of work to do, isn’t it? Lithium-ion batteries certainly suit you the best if you’re a lazy bum.
Self-Discharge Rate
Well, it’s a little bit technical, so instead of boring you with lengthy deets, let’s cut it short: Internal reactions within the batteries make them lose charge over time and ultimately reduce their capacity.
The self-discharge rate of a lead-acid battery is 33%, which is no doubt enormous. However, in the case of lithium-ion batteries, self-discharge varies between 2% and 3% and if you leave them unplugged for almost a season.
Lifetime Cycles
Even the best lead-acid batteries have a cycle span of 500–1,000 cycles, and if you’re frequently tapping into your battery bank, that could mean that your batteries may need a replacement within a year or two.
On the contrary, lithium-ion batteries come up with a cycle span of around 5,000 cycles, thus providing five times more longevity than an ordinary lead acid battery.
Charge Time
Lead-acid batteries generally require about 8–10 hours for a 100% charge, whereas lithium-ion batteries require a minimum charge time of 2–3 hours.
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Which 12V Battery Has Better Chemistry with the Tesla Model 3?
Lithium-ion batteries have definitely better chemistry than the Model 3. The following video from Tesla Raj YouTube channel perfectly summarizes the reasons for this claim:
Summary:
| Lead-Acid Battery |
| ✅ Economical (costs around $340) |
| ✅ Too heavy (weighs approx. 330 lb) |
| ✅ Requires frequent maintenance |
| ✅ 33% self-discharge rate |
| ✅ Around 500–1,000 lifetime cycles |
| ✅ Charge time takes 8–10 hours) |
| Lithium-Ion Battery |
| ✅ Expensive (costs around $1,300) |
| ✅ Lightweight (weighs approx. 75 lb) |
| ✅ Requires no maintenance at all |
| ✅ Minimal discharge rate of 2%–3% |
| ✅ Around 5,000 lifetime cycles |
| ✅ Charge time takes 2–3 hours |
Where to Buy a Tesla Model 3 12V Battery? Is There Any Aftermarket Replacement Available?
The Tesla OEM 12V battery comes with a four-year or 50,000 miles warranty. So if your battery dies within warranty, you are highly recommended not to buy a new battery as you can get it replaced for free at any nearby Tesla service center.
In other cases, you can either go to a Tesla service center and get your battery replaced or go for aftermarket options.
We have a detailed article on whether aftermarket 12V batteries are a wise investment or not.
But for the sake of this article, I’ll only share that yes, there are companies such as Ohmmu which are pretty popular in the Tesla community that offer OEM 12V battery replacements.
While the products are undoubtedly great, they don’t work well with Tesla.
No, no… Not the car. The whole company!
Intrigued? You better go through this link first then.
How to Replace a 12V Battery in Tesla Model 3?
Tools You’ll Need
- 10 mm wrench/ratchet
- 12V battery
- Gloves
Steps:
- Start by opening the frunk.
- Keep a door or a window open to avoid yourself getting stranded.
- Shut down your automobile fully using the touch screen (Menu > Security & Safety > Power Off).
- The rear seat has a clip on both sides. Unlock them (two clips) and lift the passenger side seat.
- Before your eyes, a dark cover will appear. Take it out (tools not required).
- You will notice a rectangular clip underneath their release and let it drop to the side.
- Return to the frunk and unscrew the upper lid. Be cautious since some clips can easily burst and shatter.
- Remove the vent cover to gain access to the 12-volt battery.
- Remove the bolt from the top using two supporting bars.
- You’ll see that the negative side is first (in black), followed by the positive (red).
- Remove the battery after disconnecting everything.
- Connect the +ve and -ve of the new Ohmmu battery using adapters. (Adapters are included with the battery.)
- Tighten the bolts and support bars after installing the new battery in the rack.
- Put on the positive (red) first and then the negative (black).
- Following this section, your Tesla will make a whirring noise.
- Reinstall all the vent and backseat covers precisely.
- Insert the high-voltage plug again and cover it.
- Set the seats back in place.
To further comprehend this process, check out this video by TESBROS on their official YouTube channel:
Common Tesla Model 3 12V Battery Issues – and How to Solve Them
Even though all vehicles (electric and non-electric) have a 12V auxiliary battery, batteries used in Teslas have a greater tendency of dying out early.
Model 3 owner jcanoe had very interesting insights on the subject matter:
The things that cause a 12V lead-acid battery to fail prematurely are load, heat, vibration and time. You can monitor the voltage of the 12V system from the 12V accessory port with a voltmeter or a USB adapter with a built in voltmeter (under $10).
At some point Tesla reprogrammed the charging routine for the 12V battery as they were probably overcharging the 12V batteries and causing the 12V batteries to fail. This change may have helped extend the life of the 12V battery.
As Tesla was continuously trying to fix the rapidly dying 12V battery issue, they were observed getting rid of it with the help of a software update as mentioned in the above comment, but it didn’t turn out as expected.
But then Elon Musk, in an interview with Sandy Munro, confirmed that they have finally moved all Tesla models to a lithium-ion battery to nip this issue in the bud for forever.
Elon Musk said,
We’re finally transitioning to a Li-ion 12-volt battery. It has way more capacity and the cycle life matches the main battery pack. We should have done that before, but it’s great that we are doing it now.
Though some minor glitches of Li-ion battery were claimed by some Tesla owners in Europe (having the LFP Model 3), causing it to die really soon just like lead-acid batteries and leaving the vehicle stranded and undrivable.
Since it’s new in the system as of this writing, it will be really early to claim any malfunctioning Li-ion batteries.
Frequently Asked Questions About Tesla’s Model 3 12V Battery
What happens if a Tesla 12V battery dies?
Tesla’s 12V auxiliary battery is responsible for powering up cars’ sensitive electronics like lights, indicators, computers, locks, sensors, etc.
If, by any chance, your 12v battery dies out while you’re on a drive, all car systems will cease immediately, and you’ll be stuck. You won’t be able to charge your Tesla’s main battery too.
How much does a Tesla Model 3 12V battery cost?
If the warranty of your Model 3 hasn’t expired, the cost to replace the 12-volt battery will be $0 as it’s covered under warranty. But if your warranty has expired, expect to pay anywhere around $150 to $300.
I can’t give an exact number as the 12V battery replacement cost depends on several factors such as the type of your car (LR, SR+, Performance), the area you’re living in, etc.
Can I replace Tesla’s 12V battery myself?
Yes, you can replace Tesla’s 12V battery yourself.
If you are at home and have all the equipment available, you can easily replace your car’s battery. All you have to do is simply follow the step-by-step guide I have elaborated above.
But if your battery goes dead while you’re cruising on the road, you don’t have enough options left but to call Tesla roadside assistance.
How to provide a jump-start to flat Tesla 12V batteries?
Simply follow these steps to jump-start your Tesla:
- Get a 12V battery or access a 12V charging station ASAP.
- To allow the 12V systems to start up, connect a 12V jumper or charger to the 12V battery.
- To avoid any difficulties, we recommend charging the 12V battery for at least five minutes before attempting to do anything with the car, including charging it.
- Connect the vehicle to a vehicle charger or the UMC.
- Avoid using fast chargers; the charge rate is going to be real slow in the beginning.
- Charge the automobile to a reasonable level and then charge freely on whatever charger you like.
Note: This is a matter of last resort. Don’t rely on this fix. You are advised to keep your main battery charged to an adequate level.
Final Thoughts
Ah, the satisfaction!
This guide really messed with my brain; it’ll be appropriate to use the phrase “turned my brain into yogurt”!
There were so many minor yet significant details that I dug through Tesla forums and newsletters. But in the end, it’s all worth it.
I hope this guide has cleared all your queries related to the Tesla Model 3 12V battery; the OEM as well as the aftermarket ones.
If there’s anything you’d like to add, feel free to comment down below.
Muhammad Hassan
Engineer by trade and writer by passion, Hassan is an automotive enthusiast who thinks EVs are the future. At TTU, he discusses the coolest features and products Model 3 owners look for -- so they can better experience their cars. In his free time, he enjoys tea, reading, and listening to podcasts.These 5 rare tips can save you so much time and stress – and few owners know about them (even after years of ownership). Sign up below to learn more. It's free!
