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What color do you connect first on a car battery?

Quick Answer

The proper order to connect cables to a car battery is:

  1. Connect the red positive (+) cable to the positive terminal of the dead battery first.
  2. Connect the other end of the red cable to the positive terminal of the good battery.
  3. Connect the black negative (-) cable to the negative terminal of the good battery.
  4. Connect the other end of the black cable to a metal ground on the dead car, away from the battery.

So in summary, you always connect the red positive cable first, followed by the black negative cable. The very first connection should be the red cable to the dead battery’s positive terminal.

Why Red First?

There are a few important reasons why you want to connect the red positive cable first when jump starting a car:

  • It prevents sparking near the battery – Connecting the positive first avoids causing sparks near the battery itself. Sparks can be dangerous around the flammable hydrogen gas produced by lead-acid batteries.
  • Avoids short circuiting the good battery – Attaching the negative cable first can accidentally short circuit the good battery you are using for the jump start. Short circuits can damage the battery.
  • Establishes a ground reference – Connecting positive first allows you to establish a reference ground for the dead battery you are trying to jump start.
  • Allows current flow in the proper direction – Current needs to flow from the good battery to the dead battery. Connecting positive first ensures the flow is correct.

So in essence, connecting the red positive lead first helps orient the electrical connection in the proper direction and avoids possible sparks or short circuits near the battery. The positive terminal should always be the first live connection when jump starting a vehicle.

Step-by-Step Jump Start Procedure

Here is a step-by-step guide to safely jump start a car battery using jumper cables:

  1. Check the batteries – Before connecting anything, inspect both batteries. Make sure they are the same voltage (12V) and about the same size. Check that the dead battery is not cracked, leaking, or damaged. Also check the water level and add distilled water if necessary.
  2. Position the vehicles – The vehicles should not be touching. Turn off both vehicles and all accessories, lights, radio, etc. Engage the parking brakes.
  3. Connect the red positive (+) clamp to the dead battery’s positive terminal first. – Take care not to touch the positive and negative clamps together, and avoid leaning over the battery.
  4. Connect the red positive (+) clamp to the good battery’s positive terminal. – Again be careful not to touch the clamps together or to the vehicle.
  5. Connect the black negative (-) clamp to the good battery’s negative terminal.
  6. Connect the black negative (-) clamp to a bare metal ground on the dead vehicle’s engine block. – Do not connect the black clamp directly to the negative battery terminal, which can cause sparks.
  7. Start the vehicle with the good battery – Let the vehicle run for a few minutes to charge the dead battery.
  8. Start the vehicle with the dead battery – Try to start the disabled vehicle. If it doesn’t start after a few tries, let the good vehicle continue to charge the dead battery for a few more minutes.
  9. Remove the jumper cables in reverse order – Take off the black cable from the dead vehicle’s ground first. Then remove the black cable from the good battery. Then remove the red cables in the same order they were put on. This avoids sparks near the battery.
  10. Let the jump started vehicle run – Let the previously dead vehicle run for at least 30 minutes to recharge the battery after removing the jumper cables.

Following this proper sequence and process safely jump starts a dead battery while avoiding battery damage or personal injury.

Battery Basics

To understand why connecting the red positive first matters, it helps to understand a little bit about lead-acid car batteries and how they work:

  • Car batteries provide 12-volt DC electricity to power all the vehicle’s electronics and start the engine.
  • Inside are lead plates immersed in an electrolyte solution of sulfuric acid and water.
  • A chemical reaction between the lead plates and sulfuric acid generates electrons, creating electricity.
  • The battery has six individual cells, each producing 2 volts to give a total 12 volts.
  • Each cell has a positive and negative plate, the positive plate is lead dioxide, the negative is sponge lead.
  • The positive and negative terminals on the battery connect to the positive and negative plates in each cell.

When a battery is dead, the chemical reaction can no longer generate enough electricity. Jump starting uses the good battery to provide the extra power to get it going again.

Connecting positive first sends current into the dead battery in the right direction to re-energize the chemical reaction. Getting the flow wrong by connecting negative first won’t work or can damage equipment.

Understanding the basics of how a lead-acid battery works makes it clear why proper cable order matters.

Battery Terminal Identification

If you aren’t sure how to identify the positive and negative terminals on a battery, here are some tips:

  • The positive terminal will generally be larger than the negative terminal.
  • There may be a + or – symbol near each terminal, as well as red/black indicator colors.
  • The battery case itself is normally marked indicating positive and negative.
  • Some manufacturers shape the terminals differently, the positive terminal may be rounded/convex and the negative terminal is flat/concave.
  • If no indicators are obvious, check your vehicle’s owner manual for guidance.

Being able to properly distinguish the positive and negative terminals is critical during jump starting, so take a close look before connecting any jumper cables. If you aren’t 100% sure, look up battery images for your specific vehicle make and model to verify. Don’t guess when in doubt.

Safety Tips for Jump Starting

Although jump starting a battery is generally safe if procedures are followed, there are some safety precautions to keep in mind:

  • Always wear protective gear – Wear eye protection and gloves when handling batteries and jumper cables.
  • Avoid touching both terminals – Do not allow the red and black clamps to touch each other or another common metal surface. This could cause a dangerous spark or short circuit.
  • Do not lean over batteries – Always keep your face and body as far away from the batteries as possible during connection. Batteries can expel explosive gases and corrosive acid.
  • Check for flammable gas – If the dead battery is very low or damaged, flammable hydrogen gas may have built up around it. Check the battery vents before jump starting.
  • Avoid connecting to carburetors or fuel lines – Only connect the negative clamp to bare metal engine components, away from fuel sources.
  • Use properly sized jumper cables – Cables need to be robust enough to handle the required current without overheating.
  • Only jump similar voltage systems – Only use 12V systems to jump other 12V vehicles. Do not try to jump start a 6V or 24V battery.

Exercising caution and following manufacturer recommendations will allow you to safely jump start your vehicle battery.

Maintaining Your Battery

To help avoid needing jump starts, be sure to properly maintain your vehicle battery:

  • Regularly check battery posts and clean any corrosion
  • Coat battery terminals with dielectric grease or spray to prevent corrosion
  • Make sure battery clamps are tight but not overtightened
  • Check the battery’s age, most last 3-5 years
  • Visually inspect the battery case for damage
  • Check and fill battery fluid if applicable
  • Have the charging system tested annually
  • Avoid draining the battery completely
  • Consider a battery tender/trickle charger during long storage periods

Proper maintenance extends battery life and ensures your vehicle starts when you need it.

When to Replace a Car Battery

If your battery is more than 3 years old, it’s a good idea to test it and consider replacement. Warning signs include:

  • Difficulty starting the car, especially in cold weather
  • Dim headlights when idling
  • Battery case damage or severe corrosion
  • Visible cracks, bulging, or a loose top cover
  • Fluid leaks or very low electrolyte level
  • Sulfate buildup on the battery posts

Most auto parts stores can test your battery capacity and confirm if it should be replaced. Waiting too long increases the chances of being stranded with a dead battery.

Using a Portable Jump Starter

While jumper cables and another vehicle is the primary method for jump starting a car, portable jump starters provide an alternative:

  • Smaller units can fit easily in your trunk or glove compartment
  • No second vehicle required, just charge the jump starter periodically
  • Safer than handling jumper cables
  • Many models include power outlets, flashlights, and emergency lights
  • Simpler operation – just attach the clamps and turn on the starter

Portable units typically contain rechargeable lithium batteries capable of multiple jumps when fully charged. However, check the requirements as larger engines may need a higher capacity starter.

Always follow the manufacturer’s instructions closely when using a portable jump starter. While very convenient, they still need to be used properly to avoid battery or vehicle damage.

Calling for Roadside Assistance

Rather than risk injury or further vehicle damage, it may be best to call for professional roadside assistance if:

  • You aren’t comfortable or familiar with jump starting procedures
  • Don’t have access to jumper cables or a functioning vehicle for a jump
  • The battery is damaged or leaking
  • You are stranded in a dangerous location
  • The vehicle requires a Heavy Duty jump start

Most auto insurance policies and vehicle manufacturer’s include roadside assistance programs and emergency battery jump services. The peace of mind is often worth the annual fee for coverage.


Remember, when jump starting a car, always connect the red positive cable first. Attach it to the dead battery’s positive terminal first, followed by the good battery’s positive terminal. Connecting the positive lead first establishes current flow in the proper direction, avoids sparks near the battery, and prevents system damage.

With the correct cables in the proper sequence along with basic safety precautions, jump starting a dead battery is a relatively simple process. Maintaining your existing battery through regular testing and preventative care reduces the chances of being stranded with a dead battery. But keep a set of jumper cables and portable jump starter handy just in case.

Color Attach To
Red Dead battery positive terminal first, then good battery positive terminal
Black Good battery negative terminal, then metal ground on dead vehicle

This summarizes the proper jump start cable order. Following these steps ensures you safely jump start your battery to get your vehicle running again.