Question

One cold winter morning the temperature is well below 0°F. In trying to start your car, you run the battery down completely. Several hours later, you return to replace your fouled spark plugs and find that the liquid in the battery has now frozen even though the air temperature is actually a bit higher than it was in the morning. Explain how this can happen.

Short answer

On cold winter mornings, the liquid in batteries gets freezing because the liquid battery is recharged at 0.3 degrees Celcius. The temperature is less than 0.3 degrees Celcius, and the batteries start to freeze.

Step-by-step solution

The given data

The temperature is below 0°F.

The Lead acid battery in vehicles

At present, the lead acid battery is a widely used rechargeable battery in vehicles. A 12 V lead storage battery comprises six 2.0 V cells connected in a series and housed in a hard rubber or plastic case.

These batteries designed for use in vehicles are not allowed to discharge completely. The alternator is driven by the engine and charges the battery continuously.

About$1.8\times {10}^7\mathrm{J}$ can be provided an average automobile battery before it needs recharging. A current as large as 100 A is available for the short time needed to start the engine.

The liquid in batteries gets frozen in winter

The liquid battery is recharged at $0.3^{\mathrm{o}}\mathrm{C}$when the temperature is less $0.3^{\mathrm{o}}\mathrm{C}$then, the battery starts freezing. Once the lead-acid batteries were undergone discharge, it causes permanent damage.

Hence we must keep the batteries always fully charged. The car battery started to go down completely when the temperature was observed in the winter morning below $0^{\mathrm{o}}\mathrm{F}$.

Even though we had replaced the fouled spark plugs, the battery was still freezing. This is because some of the charges to start the engine increases the temperature of the air. Thereby the temperature is higher than it was in the morning.