Peukert

Peukert refers to a relationship in battery science known as Peukert's law, named after Wilhelm Peukert, a German researcher who described the effect in the late 19th century. The law states that the usable capacity of a battery is not constant but decreases as the discharge current increases. In other words, drawing current quickly reduces the amount of energy that can be delivered compared with a slow, gentle discharge.

A key feature of Peukert's law is the Peukert exponent, a parameter that characterizes how strongly capacity declines with higher current. For real chemical batteries, the exponent is greater than 1, meaning non-ideal behavior, while an ideal, perfectly efficient source would have an exponent of 1. The law provides a simple, empirical model that helps engineers estimate runtime and compare battery types under specific load conditions.

Applications of Peukert's law are common in sizing and performance prediction, particularly for lead-acid batteries used in vehicles, stationary storage, and emergency power systems. The model depends on variables such as battery chemistry, age, temperature, and state of charge, all of which influence the exponent and the associated constants. While useful, the law has limitations and may not capture all dynamics of modern batteries, especially under varying temperatures or with rapid, high-rate charging and discharging. More advanced models can incorporate temperature effects and state-of-health factors to improve accuracy.

See also: Peukert's law, battery capacity, discharge rate, energy storage efficiency.