Corroded battery terminals interfere with electrical connections, leading to issues like dimming headlights, erratic dashboard warnings, and that dreaded click sound when you start the engine.
The fix?
Replacing the battery terminals.
Keep reading to explore the process of battery terminal replacement and warning signs of corroded ones so you can spot them early. We’ll also share some practical tips to keep car batteries in top shape.
This Article Contains:
- 6 Major Causes of Corroded Battery Terminals
- How to Replace Car Battery Terminals (Step-By-Step)
- How Much Does It Cost to Replace Battery Terminals?
- How to Test New Battery Terminals
- When Should You Replace Battery Terminal Connections?
- How to Maintain Battery Terminals
6 Major Causes of Corroded Battery Terminals
Here are the common culprits of battery terminal corrosion in lead-acid batteries:
- Vented hydrogen gas: When a battery charges, it releases hydrogen gas that mixes with acid vapors escaping from the electrolyte inside the battery. This reaction corrodes the terminal clamp and leads to buildup on the battery terminals over time.
- Electrolyte leakage: A leaking battery may release sulfuric acid, which can corrode the terminal clamps.
- Overfilling: Excess battery water leads to electrolyte overflow and terminal corrosion.
- Overcharging: A faulty voltage regulator or alternator can overcharge the battery, increasing its temperature and causing the electrolyte to evaporate. This can corrode the battery terminals and other wirings.
- Chemical reaction: Acid vapors and electrical current can react with exposed copper of the terminals forming corrosive copper sulfate, which damages the terminal clamp.
- Aging: Car batteries become more susceptible to corrosion, and their performance can decline after 2 to 5 years.
Now that you know what’s causing the corrosion, the next step is to swap it out.
Let’s find out how that’s done.
How to Replace Car Battery Terminals (Step-By-Step)
Modern cars have complex electrical systems that need careful handling. For instance, disconnecting the battery incorrectly can reset critical settings or even lead to electrical shorts. Moreover, handling a heavy battery with corrosive acid requires extra care.
So, the best option is to hire a professional mechanic for the replacement job.
Here are some tools they’ll require:
- Replacement battery terminals
- Car battery memory saver
- Multimeter
- Hacksaw
- Joint pliers
- Wrench or socket set (commonly 10mm)
- Battery terminal puller
- Cable cutters
- Wire brush
- Wire stripper
- Battery terminal cleaner or baking soda solution
- Hand gloves
- Safety goggles
- Blow-dryer or heat gun
- Heat shrink tubing
- Anti-corrosion spray or terminal grease
Once your mechanic has everything they need, here’s how they’ll change the car battery terminal:
- Turn off the engine and pop the hood.
- Inspect the battery cable, the battery tray, and the battery terminal for signs of corrosion.
CAUTION: A battery contains sulfuric acid, which can cause severe burns. For added safety, the mechanic will wear gloves and goggles while lifting the battery from the battery tray.
- Loosen the car battery terminal nut with a ratchet and disconnect the old terminal from the battery post. They’ll start with the negative terminal and cable to prevent sparks or electrical shorts.
NOTE: They’ll look for the positive (+) and negative (-) markings on the old battery. The positive one is a red cable or has a red cover, while the negative cable is black. The negative terminal is always disconnected first. Once the mechanic installs new terminal connections, they’ll reconnect the positive or red cable first, followed by the negative one. - Use a towel to remove the old battery terminal clamp from the battery post.
- Undo the battery terminal nut facing upwards. Then, they’ll remove the wire plate and the anti-corrosion washer that connects the battery cable to the old terminal.
- Clean any corrosion on the battery post or wiring using a battery terminal cleaner spray or baking soda.
- If the wires have excessive corrosion, they’ll use a plier to hold the terminal and a wire stripper to cut the damaged section.
- Use heat shrink tubing to seal any exposed wire. This provides insulation and corrosion protection.
- Install the new battery terminal. They’ll secure the battery terminal end, wire plate, and anti-corrosion washer to the wires by tightening the upward-facing nut.
- Repeat the entire process for the positive terminal and cable.
- Now, they’ll tighten the nut facing sideways and use a shim if the terminals don’t fit well. Shims are metal sleeves that help terminals fit securely on battery posts.
- Apply anti-corrosive spray and dielectric grease to the negative and positive battery terminals.
NOTE: If you have a dead battery instead of defective terminals, recharge it using a battery charger. Alternatively, you can charge a dead battery using jumper cables connected to another car.
Wondering how much a mechanic can charge you for this process?
Keep reading to find out.
How Much Does It Cost to Replace Battery Terminals?
A battery terminal replacement can cost around $20 to $30, including labor.
Thankfully, it’s not one of those costly repairs that car owners dread, like replacing spark plugs or an engine block.
However, simply replacing the battery terminals isn’t enough, you also need to ensure the replacement works.
How to Test the New Battery Terminals
Your mechanic will need a multimeter to conduct a few critical tests and fix poor electrical connections (if any):
A. Battery Voltage Test
- Insert the multimeter or the red test lead into the ‘Volt’ or ‘Ω’ (for Omega/Ohms) receptacle or port.
- Put the black test lead into the multimeter’s common ground port.
- Set the multimeter to 12V direct current (DC).
- Connect the positive or red test lead to the positive battery terminal.
- Connect the negative or black test lead to the negative battery terminal.
The multimeter should display a reading of around 12.6V for a battery voltage test. Additionally, when they reverse the leads, the reading should be -12.6V.
B. Voltage Drop Test
If you have starting troubles, the mechanic will check for excessive resistance in the battery cables and connections. Here’s how:
- Set the multimeter to volts.
- Place its red probe on the battery’s positive terminal and the black probe on the starter motor’s positive terminal.
- Crank the engine and check if the voltage is less than 0.5V. If it’s above 0.5V, you might have high resistance in the battery cables and connections.
- Next, place the red probe on the engine block or chassis ground to check the negative (ground) cable.
- Put the black probe on the negative battery terminal.
- Start the engine and ensure the voltage is less than 0.3V. If it’s above 0.3V, you might have resistance in ground connections.
If you have charging issues, they’ll look for resistance in the charging circuit:
- To test the positive side, place the red probe on the alternator’s B+ (output) terminal and the black probe on the battery’s positive terminal.
- Run the engine and check if the voltage is below 0.3V. If it’s above 0.5V, you might have resistance in the charging wire or connections.
- Next, place the red probe on the alternator case to test the ground side and set the black probe on the negative battery terminal.
- Start the engine and see if the voltage is less than 0.2V. A reading above 0.3V signals poor alternator grounding.
C. Resistance Test
- Set the multimeter to the Ω symbol.
- Keep the key in the “off” position.
- Connect the negative test lead to one of the battery terminals and the positive test lead to the same battery terminal post.
- The multimeter should give a reading of 0.002Ω or less.
- Repeat the same steps for the other terminal.
If the reading is more than 0.005Ω, they’ll check for any poor electrical connections between the battery terminal and the post.
Unsure when to get a battery terminal replacement?
Check the key warning signs of failing terminals that can shorten the battery life.
When Should You Replace Battery Terminal Connections?
Consider replacing your car’s battery terminals if you notice:
- A flickering check engine light
- Loss of power in electrical components (e.g., dim cabin lights)
- Persistent, bluish-green corrosion buildup on battery terminals
- Cracked, split, or worn terminal coatings
- Loose battery connections
- Difficulty starting the engine
Like any other car part, battery terminals need a little upkeep to stay corrosion-free and have a better battery life. Scroll down for some expert maintenance tips.
How to Maintain Battery Terminals
To keep battery terminals in good condition and avoid costly repairs:
- Ensure that the terminals are not too tight, as overtightening can damage the posts.
- Use copper compression terminals to distribute the electric current evenly and prevent corrosion.
- Apply anti-corrosion spray or terminal grease to protect the terminals and battery connections against moisture.
- Frequently clean the terminals using a baking soda solution and wire brush.
Call a Pro for Expert Battery Terminal Replacement
If your car’s electrical components are failing, get a battery terminal inspection to determine whether you need a replacement.
Unable to drive your car to a repair shop?
Let expert mechanics from AutoNation Mobile Service come to you.
We’re a mobile auto repair solution that offers upfront pricing and a 12,000-mile, 12-month warranty on every service, including brake pad replacement and general car maintenance.
Contact us to get a complete battery service right from your driveway.