Low-Voltage Battery AC Heating With Duty-Cycle Charge Balance
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Solution Overview
Problem
Low voltage batteries in vehicles face difficulty operating at low temperatures, necessitating an effective heating solution.
Innovation Solution
A system utilizing a unidirectional auxiliary power module to alternately flow currents through a low voltage battery, combining charging and discharging cycles to maintain temperature within a desired range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low voltage battery is used to power auxiliary devices in cold conditions, then the battery can operate, but the battery cannot effectively operate at low temperatures
Solution Approach 1:
The system applies periodic alternating current heating to the low voltage battery by cycling the unidirectional auxiliary power module on and off. During the on-period, current flows through the battery generating heat; during the off-period, the battery supplies current to resistive loads. This periodic action maintains battery temperature within operational ranges without requiring continuous external heating power.
Solution Approach 2:
The battery heats itself by utilizing its own internal resistance and the alternating current flow through it. The system leverages the battery's inherent electrical properties to generate heat internally, eliminating the need for separate external heating systems and reducing overall system complexity.
2Temperature
If continuous current flows through the low voltage battery to heat it, then the battery temperature increases, but the battery becomes overcharged or depleted
Solution Approach 1:
The system alternates between charging the battery (when the unidirectional auxiliary power module is on) and discharging the battery (when it is off and current flows to resistive loads). By adjusting the duty cycle of this periodic operation, the system maintains thermal balance while preventing excessive charging or discharging, keeping the battery within safe charge state limits.
Solution Approach 2:
The system dynamically adjusts the duty cycle parameter of the unidirectional auxiliary power module to balance heating requirements with charge state management. By changing the proportion of time the module is on versus off, the system can control both temperature rise and charge/discharge cycles to maintain optimal operating parameters.
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
Effectively heats the low voltage battery by cycling currents, ensuring it operates efficiently in cold conditions.
Implementation Method 1
The unidirectional auxiliary power module is turned on during a first part of a heating period to flow a first current through the low voltage power source... A second current is generated from the low voltage power source to a resistive load of the vehicle during the second part of the heating period
Data Source
AI summary
An electrical circuit heats a low voltage power source of a vehicle. The low voltage power source is coupled to a high voltage power source via a unidirectional auxiliary power module. The auxiliary power module is turned on during a first part of a heating period and off during a second part. During the first part, a first current flows through the low voltage power source in a first direction. During the second part, the first current is removed from the low voltage power source and a second current flows from the low voltage power source to a resistive load of the vehicle and in a second direction through the low voltage power source. A duty cycle of the heating period is selected so that a net charging power from the auxiliary power module is equal to a net discharging power to the resistive load over the heating period.