Operating temperature of the battery has a profound effect on operating characteristics and the life of a lead-acid battery. Discharge capacity is increased at higher temperatures and decreased at lower temperatures. At higher temperatures, the fraction of theoretical capacity delivered during discharge increases.
Thermal events in lead-acid batteries during their operation play an important role; they affect not only the reaction rate of ongoing electrochemical reactions, but also the rate of discharge and self-discharge, length of service life and, in critical cases, can even cause a fatal failure of the battery, known as “thermal runaway.”
Thus, under certain circumstances, it is possible to lower the temperature of the lead-acid battery during its discharging.
For lead–acid batteries, a typical number of discharge/charge cycles at 25 °C (77 °F) with respect to the depth of discharge is: It is generally considered and used in design for most applications that the end of life of a battery is when 20% of capacity is lost. It is also clear that elevated temperature reduces longevity.
The discharge state is more stable for lead–acid batteries because lead, on the negative electrode, and lead dioxide on the positive are unstable in sulfuric acid. Therefore, the chemical (not electrochemical) decomposition of lead and lead dioxide in sulfuric acid will proceed even without a load between the electrodes.
Effects on Discharge Capacity: Advantages: Higher temperatures generally result in improved discharge performance, allowing the battery to deliver more power. Challenges: Elevated temperatures contribute to accelerated positive plate corrosion and grid growth, leading to a reduced service life.