How to Jump Start a Car with a Battery Under the Back Seat or in the Trunk

Usually, the hardest part of a jumpstart is figuring out which terminal is positive.

What if, one time, you open the hood and can’t find the battery?

You might not find a car battery under the hood when you need to jump an Audi, BMW, Jeep, Mercedes-Benz or Volvo. Some vehicle makers, including Cadillac, Ford, BMW and Aston Martin, designed their car with the battery somewhere else. In fact, more than a third of all cars on the road in 2022 had a battery tucked away in a difficult-to-reach spot: under the back seat, in the trunk, behind a wheel well, etc.

Obviously, jumper cables won’t reach that.

How do you jumpstart a car if its battery is behind the passenger wheel well?

Instead of a battery under the hood, you will find a remote battery terminal. A remote battery terminal is a direct line to the positive post of your car’s battery, wherever it is in your Jeep, Ford or Volvo. It’s typically labeled with a plus sign and covered in red. To jumpstart your Cadillac, you’ll need to locate the remote terminal first, and we’ll show you how.

Follow these safety steps before we get to the actual jumpstart:

• If you hear a clicking noise, stop. Don’t try the ignition again.
• Turn off everything electronic that you can.
• Take off any jewelry.
• Get gloves and eye protection. Sunglasses would be fine.

What Does a Remote Battery Terminal Look Like?

Look for a red cap with a plus sign on it. They’ll come in a variety of shapes, and some may not be red. You’re looking for obvious symbols indicating a positive terminal. In some models, you may even find symbols indicating how to jumpstart it.

Engine designers knew there was a possibility you would need to jump-start your Cadillac, Jeep or Mercedes-Benz. Even though they made the car with the battery under the back seat or in the trunk, they built a backup plan. The terminal is in the engine compartment precisely for jumping a car when the battery is somewhere else.

5 Steps to Jump a Car That Doesn’t Have a Battery Near the Engine

Here’s the proper way to jump a car from its remote terminal:

1. Attach the red clamps first from the good car’s positive post to the red-capped remote terminal on the dead car. The good car’s positive post is usually red but not always.


2. Attach the black clamps but only one goes on a battery. Connect one black clamp to the good car’s negative post. You should clamp the other on an unpainted, metal surface like a bolt or a bracket. Near the remote terminal you might find a stud labeled for jump-starting.


3. Start your engines, first with the good car. You can wait a few minutes before starting the dead car.


4. Detach the black clamps, starting with the unpainted surface on the dead car.


5. Detach the red clamps, starting with the remote terminal and then the good car. Also, make sure they don’t touch anything.

Then go get a battery test because getting a jump can get you moving again, but it’s only temporary. That battery could fail again in less than two weeks.

There’s a real reason your Audi, BMW or Cadillac didn’t start. A battery test is the best way to find out. Go to your nearest repair shop or battery store. Ask for a full battery test. A simple voltmeter or multimeter can’t measure internal resistance, but a technician’s battery tester can. If enough resistance has built up in your battery, you might not even be able to jump it next time.

Also, a battery test can identify whether you need a professional auto repair or a simple battery replacement.

Safety Checklist Before You Jump Start a Car

Jumping a car is simple, but also potentially hazardous. Let’s talk about how to jump a car safely.

• Take off jewelry. Rings seem like an obvious hazard, but a necklace or bracelet can be just as dangerous.


• Put on gloves and glasses. Safety glasses or sunglasses, nitrile or cloth gloves — you should always protect your eyes and hands when you’re around an open engine.


• Inspect the battery connections. Corrosion at the posts can eat away at the terminals if you don’t clean it off. You might even need to replace the terminals before jump starting the car.


• Position the cars so they’re not touching. You don’t normally park cars like this anyway. However, it’s worth noting that you’re about to handle a lot of electricity. You don’t want the cars to touch because there will be an open circuit and potentially drain the good battery.


• Keep jumper clamps from touching each other. A spark from the jumper clamps could damage the power control module or any of a dozen onboard computers. You can use a simple rag or a red plastic cup to cover the clamps until you’re ready to connect them. You can jump a car in the rain, so long as you’re safely protecting the batteries and covering the jumper cable clamps.
  • Don’t let the clamps touch each other.
  • Don’t let the clamps drag on the ground or through water.
  • Don’t dangle the clamps. They might touch.


• Inspect the battery. Some obvious signs something is wrong with your car battery include:
  • Corrosion at the posts. Here’s how to clean corrosion off batteries.
  • The smell of rotten eggs. The battery may have been overcharged. Don’t try to jump the car.
  • Radiating heat. Another sign the battery has been overcharged. Don’t try to jump it.
  • Bulging or warped plastic case. A truly bad sign. The battery is not doing well. Don’t try to charge or jump it.
  • Frozen or cracked battery. A battery can be too cold to jump. If it’s frozen solid, do not try to charge it or jump it. You can warm it up, but it’s likely the case is cracked. Find a professional and get a replacement.


• Get an auto professional. If something’s wrong or you’re not confident you can jump a car safely, ask a qualified professional. They have the tools and training to handle problems you can’t anticipate when jumping a car.

Do not give a jump start with your Audi, BMW or Mercedes-Benz.

If your car has only a positive post in the engine compartment, you should not offer a jump. Yes, you could spend the time disassembling your car to find the battery — but it’s no longer safe to jump a car. The access you do get will be narrow without much room to keep the clamps safely attaching to what they should and touching nothing else.

If you feel like being a good Samaritan, the safest thing to do is carry a portable jump starter battery.

Additionally, jump starting is only for internal combustion engines. If you’re driving a Tesla or Nissan Volt, do not connect jumper cables to your car.

Prevent dead batteries by asking for this service with an oil change.

We recommend a battery test every six months or at least as often as your oil change. Car repair shops near you can test and identify weak batteries at risk of failing soon. It’s entirely possible to avoid getting a dead car dead battery if you get a battery test twice a year. Then, when a mechanic says it’s weak, replace it before it fails.

Car batteries last for three to five years, but days of high heat can shorten their lifespan by drying them out and speeding up corrosion. Too many short drives without recharging on the highway can also deplete your battery, too.