If you’ve made the switch from a traditional gas-powered car to an electric vehicle (EV), you’re not alone! As of 2024, there are hundreds of thousands of charging ports and an estimated 3.5 million electric vehicles registered in the United States.
Vehicles with high-voltage battery packs have taken the world by storm, but what happens if your electric car runs out of battery? This guide will help you understand the roles of the two batteries in your EV and what to do if they become depleted.
How Electric Cars Manage Battery Power
Most EVs have two separate batteries: a high-voltage battery and a 12-volt battery.
Auxiliary Battery
The 12V battery handles essential low-power functions, such as lights, power windows and locks, dashboard displays, climate controls, and entertainment systems. Most importantly, when you press the start button, the auxiliary battery powers the vehicle’s computer system, which engages the main battery. The main high-voltage battery then powers the electric motor, allowing you to drive.
High-Voltage Battery
The high-voltage battery, or main battery, is the powerhouse of an EV, supplying energy directly to the electric motor that propels the vehicle. This battery is significantly larger and more energy-dense than the 12-volt battery and is responsible for driving the car and sometimes, powering systems such as air conditioning and heating.
What Happens When an Electric Car Runs Out of Charge?
When an EV’s main battery charge drops to a critical level, some EVs will enter a reduced-power mode or "limp mode," depending on the model. This mode allows you to travel a short distance at a lower speed before completely shutting down, giving you a last-minute opportunity to reach a charging station or safe location.
During reduced-power mode, acceleration is slowed, and the maximum speed may be limited to around 20-30 mph. Some models will disable non-essential functions like climate control and entertainment systems. If your car does not, be sure to manually turn off those extras to give yourself as much battery as you can.
What to Do If the Main Battery Runs Out of Charge
Unlike a gas-powered car, you likely won’t be able to get a lift to the closest gas station to bring back fuel for your car. If you find yourself in a situation where your main battery has run out of charge, you will most likely need to arrange for a tow to take you to the nearest charging station.
Some companies, like AAA, offer mobile charging, but these options are currently limited and can be costly. If you have roadside assistance, request a tow truck by phone or through the company’s app. Many car manufacturers also offer complimentary roadside assistance with new vehicle purchases.
Note: Make sure the tow truck tows your EV the proper way as defined in your owner’s manual, which is likely with all four wheels off the ground.
How to Prevent Running Out of Battery in an EV
The best way to avoid being stranded is to stay ahead of your charge level. Here’s how:
- Monitor Your Battery Level: Always check your battery before driving, monitor it during your trip, and plan ahead for any necessary charging stops.
- Use Built-In Navigation Systems: Many EVs provide GPS routes and route planners that assist you in planning where to stop and charge.
- Avoid Extreme Temperatures: Cold weather can deplete battery levels faster than usual, so plan accordingly.
How Can I Tell If the Auxiliary Battery Has Run Out of Charge?
If you cannot start your car or the lower-voltage systems like locks, windows, or dashboard displays aren’t powering properly, this is likely due to a 12-volt auxiliary battery issue.
Many EVs show the charge level of both the main and auxiliary batteries. Check out your settings menu or refer to your owner’s manual for more information. You can also use a 12-volt battery tester or voltage meter, or visit your local Tires Plus, where one of our friendly and knowledgeable technicians can assist you with a free 12-volt battery check.
At What Voltage Is a 12V Battery Dead?
A fully charged 12-volt battery should read around 12.6V to 12.8V. If it drops below 12.0V, it's considered weak, and anything under 11.5V is considered dead.
- Healthy, fully charged battery: 12.6 to 12.8 volts
- Medium charge but still functional: 12.0 to 12.5 volts
- Low charge: Below 12 volts
How To Jump-Start an Electric Car 12V Battery
Can you jump-start an electric car? You sure can! If your auxiliary battery is dead, you may be able to jump-start the 12-volt battery just like you would be able to in a gas-powered vehicle. Check your owner’s manual to learn if there are any special warnings from your manufacturer. Then, grab your jumper cables and a “donor car,” and you'll be back on the road in no time.
- Locate the 12-Volt Battery – Most EVs have a 12-volt battery in the front under the hood, but check your owner’s manual for the exact location. Note that some EVs will also have special terminals that can be accessed if the power locks lose power.
- Position your donor car close enough to your EV for the jumper cables to reach the batteries in both vehicles.
- Make sure both vehicles are turned off including lights and accessories.
- Connect positive clamps (+) by attaching the red positive (+) cable to the donor car’s battery’s positive (+) terminal. Attach the other end of the red positive (+) cable to the EV’s auxiliary battery’s positive (+) terminal.
- Connect negative clamps (-) by attaching the black negative (-) cable to the EV auxiliary battery’s negative terminal. Then, connect the other end of the black negative (-) cable to an unpainted metal part of the donor car’s frame, away from the battery. Avoid connecting the black negative (-) cable to the car’s 12-volt battery, as this can potentially cause a spark and fire!
- Start your donor car and allow it to run for a few minutes to charge the dead battery.
- Start your dead car and keep it running for a while to let the 12V battery recharge.
- Disconnect the jumper cables in reverse order and place cables on the ground away from each other, any metal, or other objects. Begin by removing the black negative (-) cable from the dead car’s frame and then the black negative (-) cable from the donor car. Remove the red positive (+) from the donor car and then the red positive (+) cable from the dead car.
Don’t feel comfortable jumpstarting your car? Hitch a ride to Tires Plus! Our technicians can test, recharge, and replace your battery if needed! Give us a call first to ensure we’re able to best assist you.
Don’t Let a Dead Battery Slow You Down! Contact Tires Plus
Running out of charge in an electric vehicle isn’t ideal, but knowing what to do can make a big difference. By keeping an eye on your charge level, planning ahead, and maintaining your 12-volt battery, you can reduce the chances of getting stranded. And if you ever need assistance, Tires Plus is here to help with battery diagnostics, repair services, and replacement options for your EV.
Contact your nearest location to ensure EV services are available in your area today!
