EV Battery Load Emulator Circuit for Constant-Voltage Charging Tests
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Solution Overview
Problem
Conventional test loads, such as banks of power dissipating resistors, fail to accurately emulate the behavior of high-capacity rechargeable batteries like those used in electric vehicles, as they do not maintain a constant voltage with varying current levels, leading to improper functioning of battery charging devices.
Innovation Solution
An electrical circuit that includes a regulator circuit with a controller to maintain a constant terminal voltage by adjusting additional load elements, mimicking the behavior of a battery by absorbing and releasing current to counteract transient changes, and optionally using a pre-charge emulator to represent a battery's presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional test loads (banks of power dissipating resistors) are used, then the device complexity is reduced and ease of manufacture is improved, but the measurement precision of battery behavior emulation deteriorates because they do not maintain constant voltage with varying current levels
Solution Approach 1:
The patent creates an electrical circuit that copies the essential electrical behavior characteristics of a battery (constant voltage with varying current) without using an actual battery. The circuit uses resistors, switches, and control logic to replicate battery load characteristics, providing accurate emulation for testing charging devices.
Solution Approach 2:
The circuit dynamically adjusts its resistance by switching between multiple resistors in series/parallel configurations based on detected current levels. This dynamic adjustment allows the circuit to maintain constant voltage behavior across varying current conditions, accurately emulating battery characteristics throughout the charging process.
2Reliability
If conventional test loads are used, then the device complexity is reduced, but the reliability of charging device testing deteriorates because the test load does not accurately represent actual battery behavior
Solution Approach 1:
The circuit incorporates a detector that continuously monitors current flow and provides feedback to the control logic. Based on this feedback, the control logic adjusts the switch configuration to maintain appropriate resistance values, ensuring the circuit accurately emulates battery behavior throughout the charging process and providing reliable testing conditions.
Solution Approach 2:
The circuit changes its electrical parameters (resistance) dynamically during operation based on the charging stage. By switching between different resistor configurations, the circuit adjusts its voltage-current characteristics to match the expected battery behavior at different charging levels, ensuring reliable and accurate testing.
3Measurement precision
If high-capacity rechargeable batteries operating at very high terminal voltage and high currents are used for testing, then the measurement precision and reliability are improved, but the device complexity and safety risks increase due to the high voltage and current levels
Solution Approach 1:
The patent uses relatively low-cost, easily replaceable resistors and electronic components to create a test load that safely replicates high-power battery conditions. Instead of requiring actual high-voltage battery packs, the circuit dissipates test power through resistors that can be replaced if needed, providing a safe and economical alternative to using real high-capacity batteries for testing.
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
The circuit effectively emulates a battery's behavior, ensuring that battery charging devices operate correctly by maintaining a constant voltage and responding to current changes, thus preventing misoperation and ensuring reliable charging.
Implementation Method 1
a regulator circuit connected to the first and second terminals including: a voltage sensing circuit connected to the first and second terminals for sensing the voltage therebetween
Implementation Method 2
Such test loads are resistive and so the terminal voltage and the current flowing therethrough are related by Ohm's Law
Implementation Method 3
a voltage sensing circuit connected to the first and second terminals for sensing the voltage therebetween and providing at an output thereof a voltage that is proportional to the voltage between the first and second terminals
Data Source
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AI summary
An electrical circuit that emulates a battery, e.g., an EV battery, when being charged may comprise: terminals configured to connect to a battery charging device EVSE; and a regulator circuit 20 including: a voltage sensing circuit 22 for sensing the voltage at the terminals and providing a voltage proportional thereto; a comparator circuit 24 responsive to the difference between the voltage sensing circuit and the reference voltage VDAC; a controllable load circuit 28 connected to the terminals and including a controllable element Q1 responsive to the comparator circuit 24 for causing a current to flow between the terminals; whereby the current flowing in the controllable load circuit 28 is controlled to maintain the voltage between the terminals at a voltage that is proportional to the reference voltage VDAC.