January is one of the worst months of the year for car batteries, with vehicles left vulnerable heading into February. The cold weather over winter in January and February can often tip batteries over the edge, slowing down internal chemical reactions and eventually reducing battery power output.

At 0°C, a car battery is likely to lose around 35% of its starting power, but this can drop even further in extreme cold. Paul Gorry, vehicle expert at Auto-Trail, urged drivers to never solely rely on car dashboard warning lights to alert individuals to a fault. Instead, he explained that the rotten egg smell is a serious issue and a sign that batteries are not in a good condition.

Paul said: "If you notice a rotten egg smell coming from around the battery, it's often a sign the battery is damaged or worn out. This smell is caused by hydrogen sulphide gas, which can be released when a failing battery is overcharged.

"A healthy battery and alternator setup should not produce this gas and should definitely be changed, as not only is it another sign the battery may need replacing but it can also be harmful."

Batteries are not indestructible and may start to become flat after around three years on the road. Parking a car inside a warmer environment, such as a garage, may reduce the battery's exposure to the cold, cutting back the risk to the part.

Motorists could also consider investing in a rechargeable car battery booster, which helps maintain the component throughout the year. Car batteries are easy to replace, with motorists able to switch the part themselves or by visiting a garage.

New batteries can range anywhere from £50 to £300. However, most road users will pay between £100 and £250 for the component and labour charges at most garages.

The RAC explained that if a car won't start in cold conditions, the most likely explanation is a flat battery. They added that a vast number of RAC Patrol winter callouts are battery-related, showing the issues are widespread at this time of the year.

The RAC added: "Further signs of a completely flat battery include the ignition lights on the dashboard failing to illuminate, and the car refusing to unlock via remote central locking."