Battery State of Charge Equalization via Conditional Threshold Updates
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Solution Overview
Problem
Existing battery management systems face challenges in efficiently equalizing the state of charge across battery units with different self-discharge rates and capacities, leading to unnecessary charge balancing and accelerated aging of electronics and connections.
Innovation Solution
A method where the state of charge is conditionally updated based on a decision value calculated from the ratio of the current to previous state of charge and idle duration, only updating when the difference exceeds a threshold, and performing state of charge equalization only when the new state is higher than the previous one, thereby reducing unnecessary balancing and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If state of charge equalization is performed periodically or based on any measured state of charge value, then all battery units are balanced, but unnecessary charge balancing occurs leading to accelerated aging of electronics and connections
Solution Approach 1:
The patent changes the parameter for triggering state of charge equalization from periodic or unconditional to conditional based on threshold comparison. The decision value compares the ratio of determined state of charge to previous state of charge against a threshold, and only triggers equalization when the threshold is exceeded, thereby avoiding unnecessary balancing operations and reducing heat generation and electronic aging.
Solution Approach 2:
The system uses its own measurement data (state of charge values) to make autonomous decisions about when equalization is needed. By comparing current measurements with previous values and evaluating decision values against thresholds, the system self-determines the appropriate timing for equalization without external intervention or fixed schedules.
2Stability of the object's composition
If state of charge equalization is performed frequently to ensure all battery units are balanced, then uniformity of charge is improved, but energy is wasted through unnecessary discharge of battery units
Solution Approach 1:
The patent implements a threshold-based parameter change that compares the decision value (ratio of current to previous state of charge) against a predetermined threshold. Equalization is only performed when this threshold is exceeded, transforming the approach from frequent periodic equalization to conditionally-triggered equalization, thereby eliminating unnecessary energy discharge while maintaining adequate uniformity.
Solution Approach 2:
Instead of performing complete equalization cycles on all battery units regardless of need, the system applies partial action only when the decision value exceeds the threshold. This selective approach performs equalization only to the extent necessary, avoiding excessive discharge and energy waste while still achieving the required uniformity when conditions warrant it.
3Measurement precision
If state of charge values are updated continuously to maintain accuracy, then measurement precision is improved, but computational load and processing time increase
Solution Approach 1:
The patent changes the update mechanism from continuous to conditional by introducing a threshold-based decision value. The state of charge values are updated only when the decision value (comparing current to previous measurements) exceeds the threshold, reducing computational load and processing time while maintaining measurement precision through strategic updates at meaningful change points.
Data Source
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AI summary
The invention relates to a method for equalising state of charge in a battery that has a plurality of battery units (2-1, 2-2). This involves provision for a state of charge value for at least one battery unit (2-1, 2-2) to be ascertained, a decision value concerning whether a prior state of charge value for the at least one battery unit (2-1, 2-2) can be updated to be ascertained, the prior state of charge value for the at least one battery unit (2-1, 2-2) to be updated in order to obtain a present state of charge value for the at least one battery unit (2-1, 2-2) if the decision value concerning whether the prior state of charge value for the at least one battery unit (2-1, 2-2) can be updated exceeds a threshold value, a state of charge equalisation requirement value to be ascertained on the basis of the present state of charge value and the at least one battery unit (2-1, 2-2) to be discharged on the basis of the ascertained state of charge equalisation requirement value. In addition, a computer program and a battery management system are specified which are designed for implementing the method, as well as a battery and a motor vehicle having a drive system which is connected to such a battery.