Signs of a dead battery in a vehicle typically include:

1. Engine Cranking Slowly or Not Starting: When you try to start your car, the engine may crank slowly or fail to start altogether.
2. Dimming Lights: You might notice that your headlights, interior lights, or dashboard lights appear dimmer than usual.
3. Clicking Sound: When you turn the ignition key, you may hear a clicking sound without the engine starting. This could indicate that there’s not enough power to engage the starter motor.
4. Electrical Malfunctions: Various electrical components, such as power windows, radio, or power seats, may not work properly or may operate intermittently.
5. Foul Odor: In some cases, a dead battery might emit a foul odor, which could be a sign of a chemical reaction occurring within the battery.
6. Battery Warning Light: Some vehicles have a battery warning light on the dashboard. If this light illuminates, it could indicate a problem with the battery or the charging system.

If you notice any of these signs, it’s advisable to have your battery tested and, if necessary, replaced by a professional mechanic.

Extreme temperatures can have adverse effects on car batteries, but the specific temperature that can kill a car battery varies depending on several factors, including the type of battery, its age, and its condition.

1. Cold Temperatures: Extremely cold temperatures can reduce the chemical reactions within the battery, slowing down its ability to generate power. In very cold conditions, the battery’s capacity to provide sufficient starting power may be diminished, leading to difficulties in starting the engine. However, modern car batteries are designed to withstand cold temperatures to a certain extent, and many come with cold-cranking amp (CCA) ratings that indicate their performance in cold weather.
2. Hot Temperatures: Excessive heat can accelerate the chemical reactions within the battery, which can lead to increased water loss and internal corrosion. Over time, this can shorten the lifespan of the battery and reduce its overall performance. In extremely hot conditions, the electrolyte inside the battery can evaporate more quickly, leading to a decrease in battery life.

While there’s no specific temperature that universally “kills” a car battery, extreme temperatures—both hot and cold—can contribute to its deterioration over time. It’s essential to maintain your vehicle properly, including checking the battery regularly, especially before extreme weather conditions, to ensure it’s in good condition and to minimize the risk of failure.