Hybrid Vehicle Auxiliary Battery Sizing via DC/DC Timing Control
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Solution Overview
Problem
Conventional hybrid vehicle control devices face issues where the auxiliary battery voltage may fall below the operating voltage during high auxiliary loads before pre-startup preparation is complete, potentially preventing startup or damaging the auxiliary battery, and require larger battery capacities to account for these loads.
Innovation Solution
A hybrid vehicle control device that includes a starter motor, engine, power motor, high power battery, auxiliary battery, and a DC/DC converter, with a DC/DC operation timing control mechanism that starts the DC/DC converter only when the high power battery output exceeds a predetermined value after connecting a heavy current relay, ensuring the auxiliary battery is charged adequately and reducing the need for excessive capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the DC/DC converter starts operating after pre-startup preparation is completed (Ready ON), then the auxiliary battery can be smaller, but the auxiliary battery voltage may fall below operating voltage during high auxiliary loads before Ready ON
Solution Approach 1:
The DC/DC converter is activated in advance during the pre-startup preparation phase (before Ready ON) to charge the auxiliary battery proactively. This preliminary charging action ensures that even when high auxiliary loads occur before Ready ON, the auxiliary battery voltage remains stable and above the operating voltage threshold, preventing controller malfunction while allowing the use of a smaller auxiliary battery.
2Reliability
If the auxiliary battery capacity is increased to handle high auxiliary loads before Ready ON, then voltage stability is improved, but the auxiliary battery size and cost increase
Solution Approach 1:
The DC/DC converter operates continuously during the pre-startup preparation phase to provide continuous charging current to the auxiliary battery. This continuous useful action ensures that the auxiliary battery is constantly being recharged during the period when auxiliary loads are active, maintaining voltage stability without requiring an oversized battery to store all necessary energy in advance.
3Use of energy by moving object
If the DC/DC converter operates earlier (before Ready ON), then auxiliary battery charging is improved, but system complexity increases
Solution Approach 1:
The control system monitors the auxiliary battery voltage and the state of pre-startup preparation completion in real-time. Based on this feedback, the DC/DC converter is activated at the appropriate moment during pre-startup preparation. This feedback-based control ensures efficient auxiliary battery charging while managing system complexity through intelligent, condition-based activation rather than continuous operation.
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 solution ensures vehicle startup while maintaining auxiliary battery durability and reduces the size of the auxiliary battery by allowing earlier DC/DC converter operation, thus compensating for auxiliary loads and preventing battery damage.
Implementation Method 1
a DC/DC converter that is disposed in an intermediate position connecting the high power battery and the auxiliary battery. The auxiliary battery is charged by the high power battery via the DC/DC converter.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
To reduce the size of the auxiliary battery while ensuring vehicle startup and the durability of an auxiliary battery. A starter motor (1), a transverse engine (2), a motor/generator (4), a high power battery (21), and a 12V battery (22) that is charged through a DC/DC converter (37) by the high power battery (21) are provided. This FF hybrid vehicle comprises a hybrid control module (81) that controls the operation start timing of the DC/DC converter (37) at vehicle startup. When an ignition switch (91) is pressed, after connecting a high power relay (21 a) that is interposed between the motor/generator (4) and the high power battery (21), the hybrid control module (81) starts operation of the DC/DC converter (37) when the outputtable electric power by the high power battery is a prescribed value or greater.