Powertrain Control for Battery Thermal Management
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Solution Overview
Problem
In vehicles with electric motors and traction batteries, high accessory loads during low speeds in hot environments can lead to thermal stress, reduced system performance, and increased heat rejection, causing potential load shedding and decreased motor torque conversion efficiency.
Innovation Solution
Implementing a control strategy that adjusts engine operation, energy management, and motor boost strategies based on battery temperature and accessory loads to maintain a higher minimum state of charge and reduce power demand from the traction battery, thereby preventing load shedding and thermal de-rate conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vehicle operates with high accessory loads during low speeds in hot environments, then the accessory loads can be supported, but thermal stress increases and system performance decreases
Solution Approach 1:
The control system proactively monitors battery temperature and accessory load demands before thermal stress becomes critical. When the battery temperature approaches thresholds that would trigger thermal de-rating, the controller preemptively adjusts powertrain operation, engine braking, and accessory load management to prevent the thermal de-rate condition from occurring, thereby maintaining system performance while supporting accessory loads.
2Power
If the battery temperature is allowed to increase to support high accessory loads, then power availability increases, but heat rejection increases and thermal de-rate conditions occur
Solution Approach 1:
The control system dynamically adjusts operational parameters including minimum state of charge thresholds, engine braking torque, and powertrain mode selection based on real-time battery temperature and accessory load conditions. By changing these parameters adaptively, the system maintains power availability through optimized energy management while preventing battery temperature from reaching levels that would trigger thermal de-rate conditions.
3Temperature
If thermal management systems actively cool the battery during high loads, then temperature control improves, but system complexity and energy consumption increase
Solution Approach 1:
The system utilizes the engine and powertrain components themselves to provide thermal management functions. Engine braking generates heat that can be dissipated through the existing exhaust and cooling systems, while the controller optimizes powertrain operation to naturally manage battery thermal conditions. This self-service approach leverages existing system capabilities rather than adding dedicated active cooling 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 approach reduces heat rejection from the traction battery, delays the onset of battery chiller operation, and maintains system performance by ensuring sufficient power for high voltage loads, even under thermal de-rated conditions.
Implementation Method 1
The electric cooling system, responsive to a temperature of the traction battery exceeding a first threshold, cools the traction battery using the electric power
Data Source
AI summary
A vehicle may include an engine, a traction battery, an electric motor, an electric cooling system, and a controller. The electric motor selectively converts torque from the engine to electric power and converts electric power from the traction battery to drive torque for the vehicle. The electric cooling system, responsive to a temperature of the traction battery exceeding a first threshold, cools the traction battery using the electric power. The controller, responsive to the temperature exceeding a second threshold less than the first threshold and accessory loads exceeding a third threshold, operates one or both of the engine and traction battery to maintain the temperature below the first threshold.