Method and device for determining the actual capacity of a battery

Abstract

The present invention relates to a method and a device for determining the actual capacity of a battery using a set of characteristic curves, wherein at the beginning of a discharge process the initial voltage (UBeginn) of the battery, the discharge current strength and the temperature of the battery are determined. From this, by comparison with the data provided in the set of characteristic curves, a characteristic curve is selected and an initial state of the battery is determined. At the end of the discharge process, the final voltage (UMess) of the battery is measured. The final voltage (UMess) is compared, at the end of the discharge, with the voltage (UErwartet) expected by reason of the selected characteristic curve and, in the event that the final voltage (UMess) is smaller than the voltage (UErwartet) expected by reason of the discharge process, it is determined that the actual capacity of the battery is smaller than the available capacity assumed at the start of the discharge process.

Description

technical field [0001] The present invention relates to a method and apparatus for determining the actual capacity of a battery using a battery characteristic curve. Background technique [0002] In a motor vehicle (electric vehicle, hybrid vehicle) using a battery (rechargeable power source, secondary battery or accumulator) as the sole energy source for driving the vehicle or simultaneously with the internal combustion engine, the capacity of the battery is sufficient for the battery without recharging The mileage that the motor vehicle can travel under these circumstances is very important. [0003] It is a known fact that the amount of energy, ie the amount of current, that can be drawn from, for example, currently available lithium-ion batteries decreases with age and / or number of charge-discharge cycles. [0004] This capacity loss, commonly referred to colloquially as ageing, is characterized by a change in the characteristics of the battery during charge-discharge o...

AI Technical Summary

Problems solved by technology

[0004] This capacity loss, colloquially referred to as ageing and characterized by changes in the characteristics of the battery during charge and discharge operations (regular use) or by aging over time, is not well established

[0005] Known methods for determining capacity loss are either very complex and / or difficult to parameterize (e.g. in terms of impedance determination), or the aging models used are not comprehensive or sufficiently parameterized, which introduces large biases in the calculations

[0006] Simple methods often have the disadvantage that important parameters such as power consumption or efficiency which vary over the lifetime and use of the battery cannot be taken into account or simply determined

This open-circuit voltage, although accurate enough, can only be measured after a considerable time has elapsed after the end of the discharge process.

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