How summer heat silently drains your car’s 12‑volt battery

The 12-volt battery discharges not only in winter but also in summer. If it is neglected, it can fail during the hottest days. Why? We explain.

Temperatures significantly different from 20°C are always harmful to the battery, regardless of whether they are lower or higher. The latter accelerates the electrochemical reaction in the battery, thereby intensifying the natural self-discharge phenomenon. Under the hood of a car parked "in the sun," it gets so hot that a neglected battery often becomes completely discharged.

Few drivers realize that the summer high temperatures are most damaging to the battery. The heat exposes the battery to intense corrosion and self-discharging processes. If such a battery somehow withstands the summer period, it will fail in winter when it is more heavily burdened. But it wasn’t winter and low temperatures that ran it down; it was the summer heat.

"In high temperatures, the battery is immediately ready for use, its capacity does not drop, and the chemical processes speed up twice as much with every 10°C increase," explains Dariusz Chochel from ProfiAuto Serwis. "Unfortunately, this also causes the battery to wear out faster. Specifically, the grids corrode. Thus, due to high temperatures, the battery ages faster than in winter, and this happens before the fall-winter period when the battery's best condition is needed. Therefore, it is easy to conclude that the battery 'fails in winter' not because low temperatures drain it, but because it worked hard all summer and wore out, and the low temperatures only revealed it."

Like many other vehicle components and parts, the battery requires regular maintenance. Battery maintenance involves cleaning the terminals and charging them, regardless of its charge level. This mixes the electrolyte and refreshes the battery.

"If we park the car outside the garage and it always stays in the sun during summer, and we either use it very rarely or very frequently but for short distances, this is the worst possible scenario for the battery," advises Dariusz Chochel. "We won't harm it if we charge it in the spring, summer, and fall. Charging in the spring will refresh the battery after winter, summer charging will maintain good condition during heat waves, and fall charging will prepare it for winter. If we have a good battery and take care of it in this way, we can forget about any startup problems. It is only essential to remember to use a good charger and – nevertheless – periodic checks."