Battery EOD Matching via Dynamic Current Control
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Solution Overview
Problem
Power systems with multiple batteries often experience unequal times to end of discharge (EOD), leading to premature depletion of some batteries and potential system shutdown due to mismatched discharge rates, especially when sharing loads equally.
Innovation Solution
A control circuit monitors the EOD of multiple batteries and adjusts the current drawn from each battery by controlling power converters to equalize the rate of discharge, ensuring that all batteries deplete at approximately the same time by altering the voltage setpoints or input currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple batteries share loads equally, then each battery provides equal current to the load, but some batteries deplete prematurely due to unequal discharge rates
Solution Approach 1:
The system dynamically changes the current draw parameter from each battery based on their individual state of charge and discharge characteristics. By adjusting the current parameter for each battery individually rather than maintaining equal current sharing, the system prevents premature depletion and extends overall system operation time.
2Device complexity
If batteries operate independently with equal current draw, then the system is simple to control, but the holdup time is limited by the weakest battery
Solution Approach 1:
The control system continuously monitors the state of charge and discharge rate of each battery, using this feedback information to dynamically adjust the current draw from each battery. This feedback mechanism allows the system to extend holdup time by preventing the weakest battery from depleting prematurely, while maintaining manageable control complexity through automated adjustments.
3Duration of action of moving object
If the system monitors and adjusts current draw for each battery, then all batteries deplete simultaneously extending holdup time, but the control system becomes more complex
Solution Approach 1:
The control system transitions from static equal current sharing to dynamic current allocation that adapts to each battery's real-time condition. By making the current draw dynamic and adjustable based on monitored parameters, the system achieves simultaneous battery depletion and extended holdup time while managing complexity through adaptive control rather than overly complex predetermined schemes.
Data Source
AI summary
A system includes a first power converter, a second power converter, a first battery having a time to end of discharge (EOD) and coupled to output a current to the first converter, a second battery having a time to EOD and coupled to output a current to the second converter, and a control circuit coupled to the first converter and the second converter. The control circuit is configured to monitor the times to EOD of the first battery and the second battery, and in response to the times to EOD of the first battery and the second battery not being substantially equal, control the first converter to adjust the current drawn from the first battery to change a rate of decrease of the time to EOD of the first battery. Other example systems and methods for substantially matching a time to EOD of a plurality of batteries are also disclosed.