How to power up a Tesla with a dead low voltage battery - Fearby.com
Published on 29th December 2024 by Simon Fearby
This is a very short post that will show you how you can start a Tesla with a sudden dead Low Voltage battery in an emergency. Also jump start Petrol cars with a dead battery. This is not a sponsored post. This is advice only, please read your manual and all risk is your own when jumping a Tesla or Petrol Car.
If you have a dead low voltage battery, your first point of call is to call the Tesla service team or a specialist. Do not follow my advice as I am not an expert. I would do this if I was in the Australian outback and out of phone coverage. This post is to remind myself to follow these procedures in an emergency.
Before buying an EV I researched all the pros and cons of a EV
Biggest lessons
- Carry a Tesla Universal Mobile Charger in the frunk
- Do not rely on Public Tesla Super Chargers (Use https://www.plugshare.com/ to find alternate public chargers as Australia has less public chargers)
- Carry a Tesla Type repair Kit in the frunk
- Carry a portable tyre pressure pump in the frunk
- Carry Type repair plugs in the frunk
- Carry a number of Charge Adapters (3Phase, Caravan, Type 2 AC to Type 2 AC, 10A, 15A) in the frunk
- Carry a 10A and 15A extension lead in case I need to charger 35M away from a plug in the frunk
This is what I carry in my frunk
Failing to Plan is Planning to Fail
One of My biggest remaining fears of not being prepared is having a low voltage battery issue causing the car to not start.
The Tesla Battery has a high voltage DC battery under the car, but it also has a low voltage battery (12V lead acid in older models and a 16V LiPo in new models) like a Petrol car that powers the computer and all the buttons. If the low voltage battery is dead it cannot startup the car circuits to then start the high voltage battery to then recharge the low voltage battery. If the low power battery dies from age or cold temperatures than the car cannot start.
The car does have a procedure to allow you to access the frunk with a parable battery (only works when the low voltage battery is dead so no one can just break in). I do carry around an Energizer A22 12V Battery for this purpose just in case.
All about the Tesla 16V LiPo Low Voltage Battery
Portable Power Pack (Tesla and Petrol Jump pack)
fyi: The following Noco Power Pack I have chosen to rescue my car (and petrol cars in need).
I decided on a NOCO – 3000A Lithium Jump Starter – GB150 UltraSafe Lithium Jump Starter as a power pack with at least 3000A. I hear if you go under 1000A the voltage provided can drop to low. The NOCO – 1500A Lithium Jump Starter – GB50 or NOCO – 2000A Lithium Jump Starter – GB70 are a good choice to start a Tesla
The GB models auto detects batteries (e.g. Lead Acid, AGM etc) and it has a manual override for non detected batteries. It has a flash light also and can charge other device.
The GB models are preferred over the newer GBX models by heavy users. This should only drop 3% charge in 12 months with no usage as long as I keep it between -20c and 50c.
Recharging is simple, I just plug in the USB C plus or the provided 12V Cigarette Lighter plug
I tested the GB150 in override mode and it delivers 12.4V
Jump Starting a Tesla
There is a procedure to start the Tesla with an external power source by connecting an External battery.
Tesla How To Access Owner's Manual - Where To Find Tesla Owner's Manual in Your Tesla Car
Recovery Process 1 (Connect External Power Source to Jump the car)
Tip: skip to 16m11s
Jump Starting a Tesla Summary (Method 1):
- Connecting the external power source to the jump points under the hood and press the override button for 3 seconds (red exclamation)
- The car can then be open it opened (then place the keycard in the centre console)
- Press the brake to start the car
- Disconnect the external power supply (max external power connect time is 20 seconds)
Recovery Process 2 (Connect External Power Source, Disconnect the 16V Battery then reconnect it)
Tip: skip to 18m02s
Jump Starting a Tesla Summary (Method 2):
- Disconnect the 16V Battery
- Connect the external power source to the jump points under the hood and press the override button for 3 seconds (red exclamation)
- The car can then be open it opened (then place the keycard in the centre console)
- Press the brake to start the car
- Reconnect the 16V Battery
- Disconnect the external power supply (max external power connect time is 20 seconds)
Note: Because the newer LiPo batteries have an internal Mosfet to protect the battery, and if the method above does now work, there is a backup procedure to leave the external power source connected, then disconnecting the 16V LiPo then reconnecting it.
If attempting to activate Transport Mode (to winch the vehicle onto a flatbed truck), the low voltage battery is not required to self-recover. Leave the power supply connected continuously until the vehicle has been secured.
Jump Start Petrol cars with a dead battery
This is how you jump start a Petrol car with the Noco Boost
Bonus Tip(s)
You Need this for your Tesla - Dead 12v Battery (Don't Get Stranded)
Still Reading, Check out this tech dive into the Tesla Model Y Low Voltage Charging System from WeberAuto (Prof John D Kelly)
2021~2025 16V Low Voltage Battery
2026 Tesa Model Y 12.8V Low Voltage Battery
Log of Petrol Cars that I have Jumped on the side of the road.
22nd April 2025 at 4PM AUDI 6 Cyl, 2.4L with another car with connected Jumper leads trying to jump it (unsuccessfully). 22c Temperature.
I connected the Noco Boost to the cars battery and turned the Noco on. Within 1 second the Noco reported that the car battery was 11.4v and the Noco proceeded to send power.
After 10 seconds, the key was turned and the car started and was able driven off. Total time 1 minute.
Lead Acid Battery Voltage Chart
Learn more about Lead acid batteries and charge levels https://naturesgenerator.com/blogs/news/lead-acid-battery-voltage-chart
Safe driving