Which terminal do you take off a battery first?

Remove the negative (–) terminal first. This minimizes the risk of short circuits because most vehicles use the chassis as ground; if your tool touches the bodywork while loosening the negative terminal, nothing happens. When reconnecting, attach the positive (+) terminal first and the negative last. Below is a detailed, safety-focused guide to doing it correctly and why it matters.

Why the negative terminal comes off first

On virtually all modern cars, the battery’s negative terminal is connected to the vehicle chassis (negative-ground system). If you loosen the positive terminal first and your tool accidentally bridges from the positive post to the body or any grounded metal, you create a direct short that can spark, weld tools, damage electronics, or cause a fire. By removing the negative cable first, you break the return path to ground, dramatically reducing the chance of an accidental short while you work.

Safe battery removal: step-by-step

The following steps outline a safe removal procedure that protects you and the vehicle’s electronics. Read your owner’s manual for any model-specific instructions before you begin.

1. Power down: Turn off the ignition, remove the key/fob, and ensure all accessories are off. If the vehicle has start/stop or proximity entry, keep the fob away from the car.
2. Wait a moment: Allow 2–5 minutes for control modules to go to sleep. On some vehicles, opening doors or the trunk can wake systems; close them again and wait.
3. Wear protection: Use safety glasses and gloves. Batteries can vent hydrogen gas and contain corrosive acid.
4. Locate and identify: Find the battery (under hood, trunk, or under-seat in some cars). Identify terminals: positive is usually red and marked “+”; negative is black and marked “–”.
5. Consider memory savers carefully: If you must preserve radio presets or seat memory, use a proper OBD-II memory saver with a stable external power source. Do not use a memory saver if you are servicing electrical components where live voltage is hazardous.
6. Disconnect negative (–) first: Loosen the negative clamp (commonly 10 mm). Lift it off the post and secure the cable so it cannot spring back or touch the terminal.
7. Disconnect positive (+) next: Loosen and remove the positive clamp, then cap or wrap the cable end to prevent accidental contact.
8. Mind the sensors: Many late-model vehicles have an Intelligent Battery Sensor (IBS) on the negative terminal. Do not pry on or strike the sensor; unplug its connector before removing the clamp if required by your manual.
9. Remove hold-downs: Undo the battery hold-down bracket. Lift the battery straight up using the built-in handle; it’s heavy—use proper lifting technique.

Following this sequence breaks the ground path early and keeps the positive lead inert while you work, sharply reducing the chance of a dangerous short.

Reinstalling or replacing a battery: correct order

These steps help ensure a solid electrical connection, protect control modules, and prevent corrosion when installing a battery.

1. Place and secure: Set the battery in its tray oriented correctly. Refit and tighten the hold-down so the battery cannot move.
2. Connect positive (+) first: Attach the positive clamp to the + post and tighten to the specification in your service manual (often in the range of 5–7 N·m / 44–62 in-lb, but verify for your vehicle).
3. Connect negative (–) last: Attach the negative clamp to the – post (or to the IBS clamp if equipped) and tighten to spec.
4. Protect and finish: Apply anti-corrosion spray or petroleum jelly to terminals after tightening. Ensure terminal covers are in place.
5. Restore systems: Start the vehicle and check for warning lights. Reset clock, radio presets, and window/sunroof one-touch functions as needed. Some brands (e.g., BMW, VW/Audi, some Ford, some Mercedes) require battery “registration” or coding when a new battery type/capacity is installed—use a scan tool or dealer service to avoid charging problems and premature battery wear.

Connecting positive first and negative last keeps the grounded chassis from completing a circuit while you’re working on the exposed positive terminal, protecting against accidental arcing.

Jump-starting: related connection order

If you’re jump-starting, the order also matters to minimize sparks near the battery.

1. With both cars off, connect the red clamp to the dead battery’s positive (+) post.
2. Connect the other red clamp to the donor battery’s positive (+) post.
3. Connect the black clamp to the donor battery’s negative (–) post.
4. Connect the final black clamp to an unpainted metal ground on the dead car, away from its battery (such as a solid engine bracket).
5. Start the donor, then the dead vehicle. Remove cables in reverse order.

Grounding the last clamp away from the battery reduces ignition risk from hydrogen gas that may be venting during charging.

Exceptions and special cases

While “negative off first, negative on last” is correct for nearly all modern vehicles, there are uncommon scenarios to know about.

• Positive-ground classics: A small number of vintage cars (mid-20th-century British and some antique makes) used positive-ground systems. On those, remove the positive first and reconnect it last. Verify your vehicle’s grounding before proceeding.
• Hybrids and EVs: High-voltage systems can be lethal. Do not attempt HV battery service. Many hybrids still have a 12 V battery you can disconnect (often negative first), but always follow the exact factory procedure, which may include removing a service plug and waiting specified times.
• IBS-equipped vehicles: Don’t strike or twist the sensor on the negative post. Some procedures require disconnecting the IBS connector before clamp removal.
• Motorcycles, boats, and powersports: Most are negative-ground; follow the same order unless documentation says otherwise.
• Battery types and locations: AGM, EFB, and flooded lead-acid follow the same terminal order. Trunk- or cabin-mounted batteries may have vent tubes—reconnect them correctly.

If in doubt, consult the owner’s manual or a qualified technician; model-specific steps can affect safety and vehicle electronics.

Safety and disposal tips

The following best practices help prevent injury and environmental harm when handling batteries.

• Avoid sparks and open flames near batteries; charging can release hydrogen gas.
• Keep metal tools away from battery tops; never bridge terminals with a wrench.
• Neutralize acid spills with baking soda, then wipe and rinse carefully.
• Recycle old batteries at auto parts stores or municipal centers; most accept them free and may offer a core credit.
• Protect electronics: disconnecting may reset modules; know radio codes or relearn procedures if applicable.
• Work in a ventilated area, wear eye protection, and secure the vehicle (parking brake on).

Proper handling reduces risks to you, your car, and the environment, while ensuring reliable operation after service.

Summary

Take off the negative (–) terminal first and reconnect it last; connect the positive (+) terminal first during installation. This order minimizes short-circuit risks on negative-ground vehicles, protects electronics, and aligns with manufacturer guidance for nearly all modern cars. Observe safety precautions, watch for special equipment like IBS sensors, and follow any model-specific procedures, including battery registration where required.

Which battery terminal do I disconnect first?

You should always disconnect the negative (black) terminal first, then the positive (red) terminal, to prevent accidental electrical shorts and damage to your vehicle’s computer system. When disconnecting the negative terminal first, if a metal tool accidentally touches the engine block or chassis while you are loosening the positive terminal, no electrical short will occur because the circuit is already broken. 
Why disconnect the negative first?

• Safety: The negative (ground) terminal is connected to the car’s metal chassis, engine, and body. 
• Preventing sparks: By disconnecting the negative cable first, you break the electrical connection. This prevents an accidental short if your wrench touches the positive terminal and the metal frame of the car simultaneously. 
• Protecting electronics: A short circuit could potentially damage the vehicle’s computer, fuses, or other electronic components. 

The correct disconnection order: 

1. Turn off the engine and remove the key: from the ignition. 
2. Identify the negative terminal: (usually marked with a minus sign or a black cable). 
3. Loosen the negative terminal clamp: with a wrench and carefully lift it off the battery post. 
4. Disconnect the positive terminal: (usually marked with a plus sign or a red cable). 
5. Isolate the positive cable: to prevent it from accidentally touching the battery or any metal surface. 

Do you connect the black or the red first?

When jump-starting a car, connect the red (positive) cable first to both the dead battery and the working battery’s positive terminals, then connect the black (negative) cable to an unpainted metal surface on the dead car’s chassis. This prevents a spark from occurring when the final connection is made and helps to avoid accidental short circuits.
 
Steps for connecting jumper cables

1. Identify terminals: Opens in new tabRed is positive (+), and black is negative (-). 
2. Connect the dead battery’s positive: Opens in new tabAttach the first red clamp to the positive (+) terminal of the car with the dead battery. 
3. Connect the donor battery’s positive: Opens in new tabAttach the second red clamp to the positive (+) terminal of the working (donor) car’s battery. 
4. Connect to the donor’s negative: Opens in new tabAttach the black clamp to the negative (-) terminal of the working (donor) car’s battery. 
5. Connect to the dead car’s ground: Opens in new tabAttach the second black clamp to an unpainted metal part of the dead car’s engine block or frame. A bracket or bolt is a good choice. 

Why the black cable goes to the chassis:
Connecting the final, negative black cable to the chassis completes the circuit, and any small sparks that occur will happen on a grounded metal point away from the battery itself, minimizing the risk of a hydrogen gas explosion from the battery.

What is the order of removing and installing a car battery?

When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.”

Do you connect red or black first on a car battery?

When installing a car battery, you should connect the red (positive) terminal first, then the black (negative) terminal. This order is important for safety, as connecting the negative terminal last allows any potential sparks from a slip of your tool to happen when the negative connection is already made, thereby completing the circuit to the car’s chassis and the negative ground.
 
This video explains the proper order for connecting and disconnecting car battery terminals: 57sHelpful DIYYouTube · Feb 27, 2016
Steps for connecting a new car battery:

1. Remove protective covers: Take off any protective covers on the new battery terminals. 
2. Attach the red (positive) cable: Secure the red cable to the positive terminal first. 
3. Attach the black (negative) cable: Next, attach the black cable to the negative terminal. 
4. Tighten the terminals: Ensure both terminals are securely tightened.