Dual Battery Pack Voltage Matching to Prevent Inrush Current
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Solution Overview
Problem
Conventional dual battery pack systems face challenges with high costs and reduced capacity due to the constant operation of high-efficiency DC/DC converters, especially in hybrid systems with heterogeneous battery packs, leading to inefficiencies and potential damage from inrush currents.
Innovation Solution
A charge and discharge control device utilizing a DC/DC converter as a power transmission channel for temporary voltage adjustment, allowing selective relay control to suppress voltage differences between battery packs, reducing the need for constant DC/DC converter operation and enabling direct power supply through relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high-output DC/DC converter is used to regulate the output voltage of the auxiliary battery pack, then the voltage control performance is improved, but the volume of the DC/DC converter increases and the overall pack capacity is reduced
Solution Approach 1:
The controller performs preliminary voltage matching between the main battery pack and auxiliary battery pack before connecting them in parallel. This preliminary action eliminates the need for the DC/DC converter to continuously regulate voltage, allowing the use of a smaller converter that only needs to handle transient adjustments rather than continuous high-output regulation.
Solution Approach 2:
The system uses the relays and controller to automatically manage the parallel connection sequence, with the DC/DC converter serving only as a supplementary voltage adjustment device rather than the primary voltage regulation mechanism. This reduces the converter's required output capacity and volume.
2Reliability
If a high-efficiency DC/DC converter is used to constantly operate while supplying power from the auxiliary battery pack, then the power supply stability is improved, but the cost of the battery pack system increases
Solution Approach 1:
The DC/DC converter operates periodically rather than continuously. The controller manages power supply through relays during normal operation, and the converter is activated only when voltage adjustment is needed. This periodic operation reduces the requirement for high-efficiency continuous operation, allowing the use of a lower-cost converter.
Solution Approach 2:
The controller acts as an intermediary that manages the parallel connection and power distribution, reducing the burden on the DC/DC converter. The converter serves as a supplementary component rather than the primary power management device, which reduces the need for expensive high-efficiency continuous operation capabilities.
3Adaptability or versatility
If two DC/DC converters are used in the active topology to enable both battery packs to be used actively, then the power supply flexibility is improved, but the cost increases and the control complexity increases
Solution Approach 1:
The system segments the power management functions: the controller handles the logic and sequencing of parallel connections, the relays handle the switching, and the DC/DC converter handles only voltage adjustment. This segmentation simplifies the control complexity compared to using two full DC/DC converters, while still maintaining the flexibility of active dual battery operation.
4Manufacturing precision
If the DC/DC converter output is increased to maintain voltage regulation during auxiliary battery pack operation, then the voltage regulation capability is improved, but the device volume increases
Solution Approach 1:
The controller performs preliminary voltage matching before parallel connection, so the DC/DC converter only needs to handle small transient adjustments rather than continuous high-power regulation. This reduces the required output capacity and volume of the converter while maintaining adequate voltage regulation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the overall capacity and efficiency of the dual battery pack system by using a smaller, less expensive DC/DC converter and prevents inrush currents, while optimizing charging and discharging sequences to enhance safety and reduce costs.
Implementation Method 1
utilizing a DC/DC converter, which is provided as a power transmission channel between an auxiliary battery pack and a load, for temporary voltage adjustment to suppress the voltage difference between the main battery pack and the auxiliary battery pack
Data Source
Figure 1
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Figure 4a
AI summary
Disclosed are a charge and discharge control device, a dual battery pack system, an electric vehicle, and a charge and discharge control method. A charge and discharge control device according to the present disclosure is configured to control charging and discharging of a dual battery pack system including a first battery pack and a second battery pack the charge and discharge control device and includes: a first relay connected between the first battery pack and a load; a second relay connected between the second battery pack and the load; a DC/DC converter connected between the second battery pack and the load; a voltage measurement unit configured to measure a first pack voltage of the first battery pack and a second pack voltage of the second battery pack; and a controller configured to control the first relay, the second relay, and the DC/DC converter. The controller controls the DC/DC converter to be turned on during a voltage control requirement period in which a voltage difference between the first pack voltage and the second pack voltage is required to be reduced while operating in a discharge sequence control mode.