Mild Hybrid Starter Generator Battery Segmentation for Low Temperature Start

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Solution Overview

Problem

Lithium-ion batteries in mild hybrid electric vehicles fail to supply sufficient electric power at extremely low temperatures, preventing engine start-up due to deteriorated energy storage and charging efficiency.

Innovation Solution

An apparatus and method that includes a mild hybrid starter & generator (MHSG), two batteries (a high-voltage lithium-ion battery and a low-voltage auxiliary battery), a low voltage DC-DC converter, and a controller that determines charging and discharging conditions to ensure the auxiliary battery is charged and can supply power to the MHSG, even at low temperatures, by using an ignition switch with multiple contact points and sensors to detect outdoor temperature and state of charge (SOC).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a lithium-ion battery is used to supply electric power to the MHSG, then charging and discharging efficiency is improved, but energy storage performance deteriorates at extremely low temperatures

Engineering Contradiction:

Improvecharging and discharging efficiencyVSAvoidenergy storage performance at low temperature

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The power supply system is segmented into two separate batteries: a first lithium-ion battery connected to the MHSG for high-power applications, and a second battery for low-temperature starting operations. This segmentation allows each battery to be optimized for its specific function, resolving the contradiction between charging efficiency and low-temperature reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The controller acts as an intermediary that manages power distribution between the two batteries and the MHSG. It determines whether to charge the second battery from the first battery based on temperature and SOC conditions, mediating between the conflicting requirements of charging efficiency and low-temperature performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the first battery supplies electric power directly to the MHSG at low temperature, then engine start-up can be attempted, but insufficient electric power is supplied due to low SOC

Engineering Contradiction:

Improveengine start-up capabilityVSAvoidelectric power supply at low temperature

Core Design Contradiction:

Ease of operationVSPower

Solution Approach 1:

The system performs preliminary charging of the second battery from the first battery when temperature and SOC conditions are favorable. This advance charging ensures that sufficient power is available in the second battery when low-temperature starting is needed, resolving the contradiction between operational ease and power availability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The controller changes the operational parameters by switching between different battery sources based on temperature and SOC conditions. When the second battery's SOC is sufficient, it is used for starting; otherwise, the system adjusts to use the first battery or charges the second battery first, adapting parameters to resolve the power supply contradiction.

Inventive Principle:

Principle #35Parameter changes

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

Enables engine start-up by supplying sufficient electric power to the MHSG even in low outdoor temperatures, ensuring reliable operation by managing battery charging and discharging conditions effectively.

Implementation Method 1

a low voltage DC-DC converter (LDC) which converts voltage supplied from the first battery into a low voltage

Methodology Applied

Scientific EffectElectrical Energy Conversion:

Implementation Method 2

a mild hybrid starter & generator (MHSG) which starts an engine or generates electric power by using an output of the engine

Methodology Applied

Scientific EffectElectromagnetic conversion:

Data Source

PatentUS10493977B2Apparatus and method for controlling start of engine for mild hybrid electric vehicle

Publication Date: 2019.12.03 HYUNDAI MOTOR CO LTD

AI summary

An apparatus for controlling a start of an engine for a mild hybrid electric vehicle includes: a mild hybrid starter & generator (MHSG) starting an engine; a first battery connected to the MHSG through a first power cable and supplying electric power to the MHSG; a low voltage DC-DC converter (LDC) converting voltage supplied from the first battery into low voltage; a second battery supplying the low voltage to an electric load that uses the low voltage; an ignition switch including a first contact point and a second contact point; a data detector detecting data for controlling the engine start for a mild hybrid electric vehicle; and a controller determining whether a charging condition of the second battery is satisfied based on the data, and charging the second battery with electric power of the first battery when the charging condition of the second battery is satisfied.