can a new car battery short out

[StBrandon]

Yes, a new car battery can short out, although it is a relatively rare occurrence. The primary risk is an internal short circuit, which happens when the insulating separators between the positive and negative plates inside the battery fail. This allows current to flow uncontrollably within the battery itself, leading to rapid overheating, swelling, and potentially even a thermal runaway event. While new batteries undergo quality control, manufacturing defects can slip through. A more common cause of a "short" involving a new battery is improper installation, where a tool accidentally bridges the positive terminal to the car's metal chassis (ground).

Here are the primary causes and their likelihood:

Cause of Short Circuit	Description	Likelihood in New Batteries
Manufacturing Defect	Faulty internal separator or plate alignment allows internal contact.	Low
External Short (During Installation)	Wrench or tool touches both the positive terminal and a grounded metal surface simultaneously.	Moderate
Physical Damage	Battery case is cracked during shipping or handling, leading to internal damage.	Low
Faulty Vehicle Wiring	A pre-existing short in the car's electrical system can overload a new battery.	Variable

If you suspect a short, the signs are often clear. The battery may get very hot to the touch, bulge, or emit a sulfurous (rotten egg) smell. In severe cases, it can leak electrolyte or even smoke. If you notice any of these signs, disconnect the battery immediately if it is safe to do so and seek professional assistance. To minimize risks, always disconnect the negative terminal first when removing a battery and reconnect it last when installing a new one. This practice reduces the chance of creating a dangerous external short circuit with your tools.

[StAdelyn]

Absolutely, it can happen. I learned this the hard way. I bought a top-brand battery, and within a week, my car was dead. No warning. The mechanic found an internal short—a defect from the factory. The battery was just plain bad. It wasn't anything I did. The good news is that this is what warranties are for. I got a free replacement, and the new one has been fine for years. It's rare, but it’s a reminder that even new things can be lemons.

[AllisonLee]

The risk is low, but it's not zero. The main danger isn't usually the battery itself, but the installation process. It's surprisingly easy to accidentally cause a short if your wrench touches the positive terminal and the car's frame at the same time. That creates a huge spark and can ruin the battery instantly. Always be mindful when working with the terminals. An internal manufacturing defect is far less common due to modern quality controls, but it's still a possibility.