The weather also has an effect on the state of charge of car batteries. Both heat and cold put a strain on the battery. Especially at sub-zero temperatures, starting problems are more common. The reason: At low temperatures, the electro-chemical reactions in the battery take place more slowly. The electrons only travel slowly, which reduces the starting power of the battery. At low temperatures, starting is also made more difficult by the thickness of the engine oil, because at temperatures below 0° C it becomes highly viscous. The starter motor needs a higher starting current to overcome this resistance. As well as this, there is an increased load due to demanding consumers such as heaters and ventilators. Low temperatures not only affect the starting power. Recharging of the battery is slower due to the cold, so that the battery needs more time to become fully charged. In addition, the maximum power output of the alternator is limited. If a large number of consumers are active, little energy remains to charge the battery.
Hot days may also cause starting problems. Outside temperature above 20° C accelerate the chemical processes in car batteries which promote self-discharge or corrosion.
Regardless of winter or summer temperatures: A large number of start-stops or stop-and-go travel, for example on the motorway, also contribute to a heavier load on the battery.
By the way…
Although battery life can be extended with proper care, just like tires and brakes, batteries are wearing parts, which only have a limited life. Because of this, the battery should be tested at every visit to the workshop. Many workshops offer a free battery test with the aid of suitable battery testers.