SOC-Based Battery Discharge Sequencing for High-Charge Degradation
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Solution Overview
Problem
Conventional battery control methods lead to degradation in battery performance due to self-discharge in high SOC states and increase errors in SOC value estimation, especially in lithium-sulfur batteries.
Innovation Solution
A battery control device and method that connect batteries in parallel for initial discharge when SOC is high and alternate connections during subsequent discharge periods, managing current rates and switching batteries to prevent continuous discharge and reduce voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If all batteries are charged and continuously discharged one by one to ensure large electrical capacity, then the electrical capacity is maximized, but the discharge performance degrades due to self-discharge in high SOC state
Solution Approach 1:
The discharge process is segmented into two distinct periods: a first discharge period where all batteries are connected in parallel and discharged simultaneously, and a second discharge period where batteries are discharged alternately. This segmentation allows the system to maximize electrical capacity during the first period while preventing self-discharge degradation during the second period by rotating batteries out of the high SOC state.
Solution Approach 2:
The invention implements periodic action by alternating the discharge of different batteries during the second discharge period. When one battery reaches a reference SOC level, it is disconnected and rotated into standby, while another battery takes its place. This periodic rotation prevents any single battery from remaining in the high SOC state for extended periods, thereby preventing self-discharge performance degradation.
2Quantity of substance
If all batteries are charged and continuously discharged one by one, then the electrical capacity is maximized, but the SOC estimation errors increase
Solution Approach 1:
By segmenting the discharge into two periods with different connection configurations, the system maintains more accurate SOC estimation. During the first period, all batteries are monitored while discharged in parallel. During the second period, the alternating discharge pattern ensures that not all batteries remain in high SOC states simultaneously, reducing cumulative estimation errors.
Solution Approach 2:
The control device monitors the SOC levels of all batteries in real-time and provides feedback to adjust the discharge strategy. When a battery reaches the reference SOC level, the system detects this and automatically switches to alternating discharge mode, thereby maintaining accurate SOC estimation throughout the discharge process.
3Ease of operation
If batteries are left idle in high SOC state, then the system can maintain readiness, but the battery performance degrades due to rapid self-discharge
Solution Approach 1:
The system implements periodic action by rotating batteries in and out of the discharge circuit based on their SOC levels. This ensures that no battery remains in the high SOC idle state for too long, as each battery is periodically cycled through discharge and rest phases, preventing self-discharge degradation while maintaining system readiness.
Solution Approach 2:
The invention introduces dynamics to the previously static idle state by continuously monitoring SOC levels and dynamically adjusting which batteries are connected to the discharge circuit. This dynamic management prevents batteries from stagnating in high SOC states, thereby maintaining both system readiness and battery performance.
Data Source
AI summary
A battery control device includes: a connector turning ON or OFF a connection state between a plurality of batteries and an output terminal to which a discharge current is output, for each battery; a controller controlling the connector such that the plurality of batteries are connected in parallel with each other to the output terminal and discharged during a first discharge period from a start time of discharge of the plurality of batteries each of which SOC is a predetermined reference value or more until a time when the SOC of at least one of the plurality of batteries reaches the reference value, and connected alternatively to the output terminal and discharged during a second discharge period from a time when the SOC of each of the plurality of batteries becomes lower than the reference value until a time when the discharge of the plurality of batteries is terminated.