Energy Storage Cell Balancing via State of Charge Reference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing energy storage systems in electric and hybrid vehicles face inefficiencies due to unnecessary energy losses from unbalanced cell charging and discharging, where balancing procedures often lead to bogus voltage asymmetries and reduced capacity utilization, limiting the state of charge and causing premature discharge limits.
Innovation Solution
A method for operating an energy storage system that involves selecting a reference cell based on state of charge and open-circuit voltage, performing initial and subsequent balancing procedures only when specific voltage and state of charge conditions are met, thereby reducing bogus asymmetries and energy losses, and optimizing balancing procedures during resting phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If balancing procedures are carried out at certain cell voltage independently of actual state of charge, then voltage asymmetry is balanced, but unnecessary energy loss and bogus asymmetry occur
Solution Approach 1:
The patent changes the balancing criterion from fixed voltage-based to state-of-charge-based. By monitoring actual state of charge values and comparing them against reference values, the system adapts the balancing procedure to the real electrical charge status of cells, avoiding balancing when not needed and thus preventing unnecessary energy loss while maintaining voltage asymmetry balance
2Stability of the object's composition
If balancing procedures are carried out frequently to balance voltage asymmetry, then cell voltage balance is improved, but charging capacity and discharging range are reduced
Solution Approach 1:
The patent changes the balancing trigger parameter from voltage-based to state-of-charge-based. By using actual state of charge measurements and comparing with reference values, the system determines when balancing is truly needed, reducing unnecessary balancing operations that would otherwise reduce charging capacity and discharging range while maintaining adequate cell voltage balance
3Productivity
If cell balancing is performed to balance different states of charge, then capacity utilization is improved, but unnecessary discharging procedures occur
Solution Approach 1:
The patent changes the balancing decision parameter from voltage-based to state-of-charge-based. By monitoring actual state of charge and comparing against reference values, the system identifies when balancing is actually beneficial for capacity utilization, avoiding unnecessary discharging procedures that waste time while still achieving effective balancing when needed
Data Source
AI summary
A method for operating an energy storage system, which includes at least one energy store with a plurality of cells and is designed to supply an electric drive system of a vehicle is provided. The method includes identifying a reference cell from among the cells, and carrying out a first symmetrization procedure for the cells at a first point in time, at which the reference cell has a first reference charge state. The method also includes carrying out a second symmetrization procedure for the cells, if the following conditions a) and b) are met at a second point in time following the first point in time: a) the voltage difference between the voltage of the cell with the lowest voltage and the voltage of the cell with the highest voltage is greater than or equal to a specified voltage difference; and b) the reference state of charge of the reference cell at the second point in time lies within a specified state of charge range, the state of charge range being determined in such a way that it includes the first reference state of charge.