Parallel Battery Pack Warming for Low-Temperature Resistance Balancing
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Solution Overview
Problem
In power storage systems where different types of battery packs are connected in parallel, variations in input/output characteristics, particularly at low temperatures, lead to inefficiencies due to differences in internal resistance among battery packs.
Innovation Solution
A power storage system comprising a first and second battery unit connected in parallel, each with a power converter and multiple battery packs, where the controller selectively performs charging and discharging operations on the second battery packs to reduce their internal resistance, thereby minimizing variations in input/output characteristics by warming them up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If different types of battery packs are connected in parallel to increase system capacity, then the system can store more energy and provide greater power, but the internal resistance varies among battery packs causing variation in input/output characteristics
Solution Approach 1:
The controller performs preliminary warming action on second battery packs by selectively charging them before they are discharged to match the output characteristics of first battery packs. This preliminary temperature increase reduces internal resistance and aligns the input/output characteristics of different battery pack types, ensuring consistent system performance when connected in parallel
2Quantity of substance
If second battery packs with higher internal resistance are used, then system capacity is increased, but their internal resistance causes greater variation in input/output characteristics at low temperatures
Solution Approach 1:
The controller dynamically changes the temperature parameter of second battery packs by controlling charging current flow. This parameter change reduces the internal resistance of second battery packs from their high low-temperature state to a lower operating state, thereby reducing the variation in input/output characteristics caused by temperature-dependent resistance
3Reliability
If warming control is performed on second battery packs, then internal resistance decreases and input/output characteristics are improved, but additional control complexity is introduced
Solution Approach 1:
The warming control utilizes the battery packs' own internal resistance and charging current to generate heat for warming. The system uses the existing charging infrastructure and battery chemistry to self-warm the second battery packs without requiring external heating devices or complex thermal management systems, thereby limiting the increase in overall system complexity
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 configuration effectively reduces the difference in internal resistance between different types of battery packs, thereby suppressing variations in input/output characteristics and improving system efficiency, especially in low temperature regions.
Implementation Method 1
When charging and discharging are performed between the second battery packs as described above, each of the second battery packs is warmed. As a result, the internal resistance value of each of the second battery packs decreases.
Data Source
AI summary
A power storage system performing charging and discharging with an external system includes first and second battery units connected in parallel and each including a plurality of battery packs connected in parallel to a power converter. The power storage system includes a controller controlling operation of each power converter. The first and second battery units include a first battery pack and a second battery pack higher in internal resistance than the first battery pack, as the plurality of battery packs. The controller selects two second battery packs from a plurality of second battery packs included in the power storage system. In a standby state where charging and discharging are not performed with the external system, the controller performs, at different timings, control to discharge one of the selected two second battery packs and thereby charge the other, and control to discharge the other and thereby charge the one.