Available energy is one of the most relevant parameters for dimensioning and design of battery systems. The discharge duration of a battery and its dependence on the amplitude of the discharge current are described by Peukert’s equation.
In practice at the beginning of a development process, development engineers are often only expected to make estimates or rapid and as reliable as possible statements about the feasibility of a storage solution or the suitability of a storage type for a project. Even when many details of the specification are still rather vague or completely unknown. Other equations describe this dependence up to very high currents, including the currents that occur during a short circuit. Not the usually described quantities current and capacity, but energy and power are the decisive parameters for the dimensioning of battery systems.
The results of this work allow to determine the basic characteristics of a cell with just few current and voltage measurements and enables to answer the fundamental questions of battery system developers. The new empirical equation allows an easy determination of the available discharge energy of lithium-ion batteries that helps to design and check the suitability as energy storage e.g. for hybrid electric vehicles. Even if all the project- and application-specific parameters are not sufficiently defined, the equation allows a fast and cost-effective feasibility study on technical conditions such as vehicle range.

Keywords: discharge energy, lithium-ion cell, electrochemical double-layer capacitors, lithium capacitors, capacity, Energy Peukert equation, constant discharge current