Vehicle Control Unit Power Split for Cold Battery Charging
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Solution Overview
Problem
HV battery charging at low temperatures is limited by increased resistance and lithium plating, leading to reduced charging current and state-of-charge levels, especially in cold regions.
Innovation Solution
A vehicle control unit (VCU) manages power distribution between charging and heating systems to optimize battery temperature and charging current, using battery models and external data to determine an optimal power split.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charging current is increased to improve charging speed, then charging efficiency improves, but lithium plating occurs and cell damage is caused at low temperatures
Solution Approach 1:
The system performs preliminary heating of the battery before charging begins. The control unit activates the heating system to raise the battery temperature to a safe operating range (above 0°C) before allowing high-current charging, thereby preventing lithium plating while enabling fast charging when needed
Solution Approach 2:
The control unit dynamically adjusts the charging current based on real-time battery temperature monitoring. When temperature is low, charging current is limited; when temperature reaches optimal levels, charging current is increased to maximum safe levels, creating a dynamic charging profile that adapts to thermal conditions
2Productivity
If heating power is increased to raise battery temperature, then charging capability improves, but energy consumption increases
Solution Approach 1:
The heating system operates continuously during the charging process rather than only before charging. This maintains the battery temperature in the optimal charging range throughout the entire charging duration, ensuring that charging current can remain at high levels without interruption, thereby reducing total charging time and overall energy consumption
Solution Approach 2:
The control unit continuously monitors battery temperature and adjusts heating power accordingly. When temperature reaches the target range, heating power is reduced or stopped; when temperature drops, heating power is increased. This feedback control prevents excessive heating and minimizes energy waste while maintaining optimal charging conditions
3Reliability
If power derating is applied to prevent lithium plating, then battery safety is maintained, but charging time increases
Solution Approach 1:
The system changes the temperature parameter of the battery through active heating, transforming the battery from a cold state (where derating is necessary) to a warm state (where full power charging is safe). By controlling temperature as a key parameter, the system enables high-current charging without lithium plating, effectively eliminating the need for power derating
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
Enhances charging efficiency at low temperatures by increasing power limits, allowing for higher current delivery and improved state-of-charge levels.
Implementation Method 1
EVs are equipped with heating systems that can use electric energy to provide heat to the vehicle components including the battery
Implementation Method 2
The cells exhibit higher resistance at low temperature which limits the amount of charging current that can be supplied to the battery
Data Source
AI summary
A vehicle control unit (VCU) for power management of a vehicle receives battery temperature data. The battery temperature data is indicative of a battery temperature of a battery of the vehicle. Based on the battery temperature compared to a temperature threshold, the VCU determines a power split for splitting a charge power provided by a charging system. The power split indicates a split of the charge power into a first part for charging the battery by the charging system and into a second part for heating the battery by a heating system. The VCU transmits information about the first part of the charge power to the charging system and information about the second part of the charge power to the heating system.