Owning a Tesla is certainly a positive but if it dies then it’s a big problem. There are two reasons why your Tesla has died. Let’s look at what they are now. and get you back driving.
Tesla’s die for one of two reasons, the 12V battery is flat or the High Voltage Battery has reached 0%.
In this article, we’ll look at how to fix the problem for each scenario.
12V Tesla Battery Dead
Every Tesla has both a 12V battery and a High Voltage Battery. The 12V battery runs all the auxiliary items in your car such as windows, media, and locking, and unlocking system.
It’s generally the locking, unlocking system that gives you the heads up there’s a problem as you can’t get into your car. But don’t worry, Tesla has thought of everything, and although you can’t unlock your car, you can still gain access to the 12V battery through the frunk.
The 12V battery fails for the following reasons:
- Something was left on
- Battery is dead
Something was left on
If something was left on in your Tesla – for a period of time – this is the most likely reason that your 12V is flat. The item that has flattened your battery is usually an interior light. Teslas are super smart and will power off if not in use but if a door is left slightly open then the light won’t go out and this will drain your battery.
The reason your door is open is unfortunately usually a child or teen has not closed the door properly. Tesla doors can be heavy and small children don’t have the strength to close them fully. Teens can be very preoccupied and more often than not (well certainly my teens) have earbuds in and can’t hear that the door hasn’t closed fully.
If it’s still bright outside then it’s hard to notice that the interior light is on and so the next time you go to drive the battery will be flat.
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Battery is Dead
Your 12V battery may also be dead because it has come to the end of its life. 12V batteries generally last about 3-5 years. You can check a battery’s voltage with a Voltmeter (if you have one). It should read 12V or just below. If you have given the battery a boost and it’s still reading below this level, it needs to be replaced.
Owners of the Model 3 and Model Y were noting that their 12V were failing very quickly, within a year of purchase. Tesla has since upgraded the 12V acid battery to a Lithium Ion battery which is 16V, with a longer lifespan and also much lighter at 1.8kg, which is better for your EV in general.
Newer models are factory installed with the new battery but if you own an older out of-warranty model and want to upgrade the new li-ion battery has a hefty price tag of between $400-$600, and will have to be checked into a Tesla Service as some changes will need to be made to accommodate the new battery in situ. Unless your battery is regularly failing it might be best to continue with the historical 12V acid.
Boosting your 12V
A flat battery will mean that you can’t access your frunk if your Tesla is locked. But Tesla has thought of everything. There is a way to open your frunk, follow the instructions below:
We can open the frunk through the tow cover on the front bumper.
- Press the top of the tow cover circle
- Pull the cover towards you
- Two wires should be visible
- One of which is usually attached to the tow cover
- One is Black and the other is Red
- Attach each wire to a booster pack (or a 9V battery will work just as well)
- Red to Red and Black to Black
- Turn the booster pack on and the frunk will then release
It’s good to have access to a 9V as for most people their booster pack lives in their frunk, which is now inaccessible. It’s something to keep in mind. You’ve gone to the bother of buying a booster pack but now can’t use it as it’s inside your locked, flat car.
When the frunk is open your 12V is hidden behind some covers at the top rear of the frunk. These covers are held in place with plastic clips. These can break quite easily, especially if they have some age, so carefully remove them and place them somewhere safe for now.
Once you have located the 12V it’s now time to boost it.
A booster pack is the best way to do this.
Connect the cables
- Red to Red and Black to Black
- The Red on your Tesla might have a cap you will have to remove
- The Black can connect to any Metal part of the car mount
- Switch on the booster
- It can take up to 15 minutes to reach a boost that is sufficient to start the car
- Depending on how flat the battery was
You can also boost from an ICE (Internal Combustion Engine) car using jumper cables. But never boost from another EV. This can damage both your Tesla and the donor EV beyond repair.
If it looks like the booster is not having the desired effect, or the voltage is not rising or holding a charge then it seems like your battery has reached the end of life. You’ll need to replace it.
This is an easy switch out if you are replacing it with a standard 12V battery. If you are considering the upgraded 16V Li-Ion battery as I said previously you should check with Tesla Service first to check compatibility. This is done through the Tesla App.
- Open the App
- Select ‘Service’
- Choose the Problem
- Explain in as much detail what the problem is
- Enter your address, time, and date that you’re available
- Ensure your Cell number is correct
The new Li-Ion batteries are expected to last 8-10 years but connections may need to be adjusted to accommodate them in your Tesla model, so always better to check with Tesla before you purchase one privately.
High Voltage Battery Dead
We’ve discussed the 12V battery being flat but what happens is your High Voltage Battery is dead. It’s a bit more of a challenge depending on where you are. You can’t jump your High Voltage Battery back to life.
There are two scenarios for a dead HVB.
- Dead battery at home
- Battery reaching 0% while out driving
Battery Dead at Home
If your Tesla is parked at home and you find that the battery is completely flat, well at least you have the ability to try and get it going again, assuming you have a power source.
The items you need to check are:
- Was it plugged in but didn’t charge?
- When was it charged last?
Plugged in but didn’t charge
If your Tesla is plugged in but didn’t receive a charge, the answer is usually that your power source had a problem or your cable is giving trouble.
No Power
No power going to your cable is either because of a power outage or an overload in the circuit, or simply that someone has unplugged your cable.
Power Outage
Power outages are more and more common these days with extreme weather events and also with more people at home reflecting a bigger draw on the power grid. Lots of power outages are now scheduled by energy companies to relieve the pressure on the grid.
Your power may already be back but might have been down all night and so your Tesla didn’t have a chance to charge. This is especially the case if you have a scheduled charging set.
If your power is back but your Tesla is not charged enough then you don’t have much choice but to sit it out and wait for the range to increase. If you have some range available then it’s worth driving to a Supercharger for a rapid boost. But if it’s totally flat then you’ll have to Uber to work or have a remote working day.
Circuit Overload
The power could also be down because of a circuit overload. If this is the case you should be able to spot that something unusual is plugged in, such as a power washer or anything with a heated element.
It might not still be plugged in but it tripped the circuit and until you flick the fuse back on your Tesla won’t be able to charge. Go check your fuse board to see if this is the case. If it is it’s also an easy fix, but again you will have a wait on your hands to get the battery back to a suitable range level.
Unplugged Cable
This is also a possibility. Someone in your garage or parking area may have unplugged your cable from the wall to plug in something else and has forgotten to replug it back in. It happens! For this reason and also to prevent a circuit overload it’s a good idea to speak with an electrician to have a separate circuit installed for a Tesla Wall Charger. This can be allocated its own breaker so your will Tesla continue to charge and won’t be affected by a power drain.
High Voltage Battery Dead while Driving
Your High Voltage Battery dying while driving or indeed away from home is a bigger issue. Tesla recommends you maintain your battery level between 20% – 80%. But sometimes keeping the battery above 20% is not always possible. You might be traveling in an area that is not as well serviced with Superchargers as you would like. If you think you’re not going to make it to the next charger it’s better to pull off the highway to a safe place with at least 2-3% still remaining in your battery rather than completely dead at 0%.
There is always a slight buffer at 0% of approximately 10-15 miles but that depends on a number of factors, including the outside temperature, your speed, and the quality (age) of your battery cells.
It’s unlikely that your car will just die. The onboard computers will notify you loud and clear to go to the nearest charger. These notifications will become more assertive as your range depletes and they’re hard to ignore.
Roadside Assistance
If your range is too low to make it to the next charger then the only option is to call Roadside Assistance.
Roadside Assistance will either send a tow truck or a recovery vehicle with a power booster. It’s usually easier to be brought to a SUpercharger by the tow truck as the booster they have are not powerful enough to give you a good charge but they are useful if your car is completely at 0%.
The tow company will transfer you to either a Supercharger or your home, whichever is nearer within a 50-mile radius.
Out-of-charge roadside assistance is not a free service even if you are still under warranty unless it is later discovered that there is a technical issue with your Tesla.
The reason it is very important to still have a slight charge in your Tesla, rather than 0% is to be able to switch your Tesla to Transfer Mode. This allows the tow truck to move your car without causing any damage to the flatbed truck.
To switch your Tesla to Transfer Mode, do the following:
- Place Car in Park
- Press and hold the Brake
- Controls – Service – Towing
- Hold until it turns ‘Transport’ to Blue
If the battery is completely dead you can no longer select this mode which in turn becomes a bigger problem when transferring your car to the tow truck. You cannot move your Tesla with no power and so the tow company will have to transfer your car using Dollies. These are extra wheels that are placed under your Tesla wheels to lift your car from the ground and allow movement to the flatbed. Moving the car without these can cause damage to the drivetrain. Not every tow company will allow for this so make sure to say this if you are at 0%. But better still not to ignore your info system.
If you are not covered by roadside assistance and calling a general tow company you must inform them that your car is an EV and must be transferred to a flatbed tow truck. A Tesla can’t be towed by the two front wheels elevated as any loose stones or debris in contact with the underside of the car can cause damage to the High Voltage Battery.
Battery Life
The lifetime of your High Voltage Battery is directly related to how well you care for your battery. According to Tesla your High Voltage Battery is expected to last 300k-500k miles or 1500 charging cycles, which is in reality the life of the car. However, if the battery is continually below 20% or above 80-90% then specific cells in your Tesla will begin to degrade and over time will no longer accept a charge.
This in turn prevents a 100% charge and reduces the overall range.
Although Tesla will replace dead batteries there will most certainly be a cost involved if the cells have died due to neglect. The cost of a full battery replacement is $20-30k! Quite the price tag. Tesla Service can easily check the onboard computers to see how the charging history has been maintained.
Returning back to a Dead Battery
How often you drive your car or charge your Tesla can also play a part in a dead battery. If you go on vacation for example and your car is fully charged, on your return it will have depleted somewhat. If you have left your car unplugged at the airport, there is a huge possibility that the battery might be at 0%. When you are on vacation, try to resist the urge to check your car.
Every time you check your car through the app you wake your car up for approximately 15 minutes. That is 15 minutes of battery use and it hasn’t even moved anywhere. You also might have activated other modes such as Sentry Mode, or Temperature Control which will cause natural Vampire Drain, of 1-2% per day. Resist the urge to check your car. No one wants to return from vacation to a dead battery and then have to sit and wait for Roadside Assist.
If you are leaving your car at home while on vacation or you don’t use your Tesla every day then you should leave your car plugged in on a scheduled timer to have a constant charge to your High Voltage Battery and keep it in tip-top shape.
I’ve written a ton on common Tesla issues, which hopefully you won’t ever experience, but if you do, we have you covered with these posts:
Check out the Tesla troubleshooting page for problem Teslas.
Check out the Tesla charging page for common Tesla charging problems.
Check out the Tesla category page for a list of popular Tesla posts.
If you are curious about other EV models, check out the EV FAQ category.
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