Battery Discharge Switching by SOC Threshold for Li-S Battery Packs
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Solution Overview
Problem
Conventional battery technologies face issues with rapid self-discharge in high SOC states leading to performance degradation and inaccurate SOC value estimation, particularly in lithium-sulfur batteries, and require inefficient discharge methods that reduce energy density and increase errors.
Innovation Solution
A battery control device that connects batteries in parallel during high SOC states and alternates discharge connections based on SOC values, using switches to manage discharge current rates and idle states, preventing continuous discharge after a reference time.
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 rapid self-discharge in high SOC state
Solution Approach 1:
The discharge process is segmented into two distinct phases: a first discharge period where all charged 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 phase while preventing performance degradation through the alternating discharge strategy in the second phase.
Solution Approach 2:
The patent implements periodic action by alternating the discharge connections of batteries during the second discharge period. After a predetermined reference time, the connection state of each battery is switched, so that batteries previously connected to the output terminal are disconnected and vice versa. This periodic switching prevents continuous discharge in high SOC state, thereby reducing self-discharge effects and maintaining discharge performance.
2Quantity of substance
If all batteries are continuously discharged one by one, then the electrical capacity is maintained, but the SOC value estimation errors increase
Solution Approach 1:
The discharge process is divided into two periods with different connection strategies. During the first discharge period, all batteries are connected in parallel, enabling accurate SOC monitoring. During the second discharge period, alternating connections allow for refreshed SOC measurements, reducing cumulative estimation errors that would occur with continuous one-by-one discharge.
Solution Approach 2:
The controller monitors the SOC values of all batteries and uses this feedback information to control the connection states during discharge. By continuously tracking SOC and adjusting connections based on predetermined reference values and reference times, the system maintains accurate SOC estimation while managing electrical capacity discharge.
3Duration of action of moving object
If batteries are left idle in high SOC state, then the system can maintain ready capacity, but performance degradation occurs due to rapid self-discharge
Solution Approach 1:
The patent applies periodic action by switching the connection states of batteries after a predetermined reference time during the second discharge period. This periodic switching ensures that no battery remains continuously connected and idle in high SOC state, thereby preventing the rapid self-discharge that causes performance degradation while still maintaining system capacity availability.
Solution Approach 2:
The controller is configured to switch connection states before performance degradation can occur by monitoring SOC values and connection duration. The predetermined reference time acts as a preliminary threshold that triggers the switching action, preventing the harmful effect of prolonged idle high SOC state before it can cause significant performance loss.
Data Source
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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.