What Would Cause a Car Battery to Short Out? Fixing

A car battery is the heart of the vehicle’s electrical system. While they are built to be robust and long-lasting, batteries can sometimes short out, leading to various problems, including the inability to start the car. In this article, we’ll explore what would cause a car battery to short out?

car battery shorted out

What Would Cause a Car Battery to Short Out?

A car battery can short out for several reasons, each compromising its ability to function and potentially posing safety risks. Here are the primary causes:

1. Internal Plate Damage

  • Vibration and Impact: Constant vibration, like that from a poorly maintained vehicle or frequent off-road driving, can cause the plates inside the battery to crack or break, resulting in a short.
  • Aging and Wear: Over time, the plates inside the battery can rust or degrade. As the plates deteriorate, the risk of them touching and causing a short increase.

2. Overcharging

  • Faulty Alternator: The alternator is responsible for recharging the battery. If it malfunctions and sends too much voltage to the battery, it can cause overheating and internal damage, resulting in a short.
  • Bad Voltage Regulator: The voltage regulator ensures that the battery receives the right voltage. A malfunctioning regulator can allow overcharging.

3. External Short Circuits

  • Improper Jump-Starting: Accidentally shorted car battery like connecting jumper cables incorrectly can cause a direct short, leading to potential battery and vehicle damage.
  • Faulty Wiring: Exposed or frayed wires near the battery can contact the battery terminals, causing an external short circuit.

4. Accumulation of Acidic Deposits

Over time, as a battery operates, it may shed active materials from its plates. These materials can accumulate at the bottom of the battery, forming a conductive layer. If this layer becomes thick enough, it can short the plates, causing the battery to fail.

5. Poor Maintenance and Cleaning

  • Corroded Terminals: A build-up of corrosion on the battery terminals can sometimes cause a short, especially if the corrosion bridges the gap between the positive and negative terminals.
  • Accumulated Dirt and Debris: A dirty battery surface can become a conductor, especially when combined with moisture. This can sometimes cause a short if the dirt bridges the terminals.

6. External Factors and Environmental Conditions

  • Extreme Temperatures: Very high and very low temperatures can affect battery health. Freezing can cause the battery acid to crystallize and expand, leading to internal damage, while extreme heat can cause the battery to overheat, increasing the risk of a short.
  • Water Damage: While batteries are designed to resist moisture, direct exposure to a significant amount of water (like in a flood) can cause a short circuit.

How do you fix a shorted car battery?

Fixing a shorted car battery is a complex task, and, in many cases, it’s more practical and safer to replace the battery altogether. If you suspect your battery has shorted internally, the best action is to get a new one. However, if you believe an external factor is causing the short, you can address the problem using the following steps:

Safety First! Before attempting any repair or troubleshooting, always prioritize safety.

  1. Wear protective gloves and safety goggles to protect against acid splashes and potential sparks.
  2. Work in a well-ventilated area as batteries release hydrogen gas, which is flammable and explosive.
  3. Disconnect the battery, starting with the negative (-) terminal followed by the positive (+) terminal to avoid accidental short circuits.

Identifying and Fixing the Issue:

  1. Inspect the Battery for Physical Damage:
    • Look for cracks, bulges, or leaks. If you see any of these signs, replacing the battery is best.
  2. Clean the Battery Terminals:
    • Over time, corrosion can build up on the battery terminals, which might cause a short.
    • Use a mixture of baking soda and water to neutralize the acid and a brush to scrub off the corrosion.
    • After cleaning, rinse the terminals with clean water and dry them thoroughly.
  3. Check the Battery Cables and Connectors:
    • Inspect for signs of wear, fraying, or damage.
    • Replace any damaged cables or connectors.
  4. Examine External Wiring and Components:
    • Ensure no external wires are touching the battery terminals, which might cause an accidental short.
    • Secure any loose wires and check nearby electrical components for any signs of malfunction.
  5. Check the Electrolyte Levels (for non-sealed batteries):
    • Low electrolyte levels can expose the lead plates, causing them to sulfate or degrade. This can lead to internal shorts.
    • If the levels are low, top up with distilled water until the plates are submerged.
  6. Conduct a Voltage Test:
    • Using a multimeter, measure the voltage across the battery terminals.
    • A fully charged battery should read around 12.6V to 12.8V. A reading below 12V indicates a potential issue.
  7. Reconnect the Battery:
    • Connect the positive (+) terminal first, followed by the negative (-) terminal.
    • Ensure the connections are tight and secure.
  8. Consider a Load Test:
    • If you’ve addressed the potential external causes and still suspect an issue with the battery, consider conducting a load test. This requires a specific tool and can be done at most auto parts stores or mechanic shops.
    • If the battery fails the load test, it’s time for a replacement.

How do I protect my car battery from a short circuit?

Protecting your car battery from a short circuit not only ensures your vehicle’s reliable operation but also enhances your safety. Here’s how you can minimize the risk of a short circuit:

Short Circuit Test YouTube
  1. Check the Battery Terminals.Look for signs of corrosion or loose connections. Corroded terminals can cause increased resistance and heat, which may eventually lead to a short circuit. Clean any corrosion using a solution of baking soda and water.
  2. Inspect Battery Cables and Connectors.Check for signs of wear, fraying, or damage. Replace any compromised cables.
  3. Ensure the battery is firmly secured in its tray. A loosely fitted battery can move and vibrate, leading to potential internal damage or even causing the terminals to touch metal parts of the car.
  4. For non-sealed batteries, regularly check the electrolyte levels. Low levels can lead to plate exposure and internal damage. Top up with distilled water if necessary.
  5. Always connect jumper cables correctly: Positive to positive and negative to negative. Incorrect connections can lead to a direct short.
  6. Ensure the other vehicle used for jump-starting has a similar voltage to avoid overloading and damaging your battery.
  7. When adding any electrical accessories (like stereo systems, lights, etc.), ensure they’re correctly installed. Poorly installed electrical components can lead to short circuits.
  8. Always use fuses for added electrical accessories. A fuse will blow in case of a fault, protecting your battery and electrical system.
  9. The alternator and voltage regulator should function correctly to avoid overcharging the battery. Overcharging can lead to overheating and internal battery damage.
  10. If you notice the battery often overcharges or undercharges, inspect your charging system.
  11. Avoid exposing the battery to extreme temperatures, both hot and cold. Consider using an insulating blanket during winter in very cold areas.
  12. Ensure the battery compartment and surrounding areas are free from debris or materials that can cause a short.
  13. Disconnect the battery if you’re doing any significant work on your car, especially involving the electrical system. Always disconnect the negative terminal first and reconnect it last.

By taking these precautionary measures, you can significantly reduce the risk of a short circuit and extend the life of your car battery. Remember always to prioritize safety when dealing with car batteries and electrical systems.

Can you charge a shorted battery?

Charging a shorted battery can be dangerous and is generally not advisable. When a battery has an internal short circuit, the plates inside have touched or deteriorated, causing a direct path between the positive and negative terminals. Attempting to charge such a battery can lead to overheating, acid leakage, or even an explosion.

Furthermore, a shorted battery will not hold a charge properly due to its compromised internal structure. Instead of attempting to recharge, it’s safer and more efficient to replace a shorted battery. Always prioritize safety and, if uncertain, seek advice from a professional before attempting to charge any questionable battery.


While car batteries are an essential component of a vehicle’s operation, they can sometimes fail for various reasons. Regular maintenance, safe driving habits, and awareness of the battery’s health can help prevent shorts and ensure a longer battery life. If you suspect your battery is shorting out or showing signs of potential problems, it is crucial to consult a professional to avoid further damage to your vehicle.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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