Dual-Battery 24V Bus Architecture for Auto Stop Power
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Solution Overview
Problem
The existing electrical systems in motor vehicles, which rely on a 12V DC bus for both DC and AC loads, face limitations in providing sufficient power to AC loads during Auto Stop events, leading to reduced fuel efficiency and increased battery drain, especially with smaller auxiliary batteries used for higher voltage buses.
Innovation Solution
A dual-battery architecture where a pair of auxiliary batteries are connected in parallel and combined with a low-voltage (12V) bus to create a higher voltage (24V) bus, increasing the available power for AC inverters and supporting high surging loads, thereby extending the duration of Auto Stop events and improving fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a separate 24V auxiliary battery and alternator are used to supply power to the DC/AC inverter, then the output power capacity is improved, but the manufacturing cost and packaging space requirements increase
Solution Approach 1:
The patent combines the 12V primary battery system and the 24V auxiliary battery system into a single integrated electrical architecture. The auxiliary battery is connected between the 12V bus and ground, creating a unified system where both batteries work together to supply the DC/AC inverter, eliminating the need for completely separate power supply systems.
Solution Approach 2:
The auxiliary battery serves multiple functions: it boosts the voltage to 24V for high-power AC loads, provides additional capacity during Auto Stop events, and can be charged by either the alternator or the primary battery. This multi-functionality allows a single component to address multiple system requirements.
2Device complexity
If small capacity auxiliary batteries are used for the 24V power net, then the cost and size are reduced, but the duration of operation without the engine running is limited
Solution Approach 1:
The patent merges the energy storage capacity of the primary 12V battery with the auxiliary 24V battery, creating a combined energy reservoir. During Auto Stop events, both batteries can discharge to support AC loads, significantly extending the duration compared to using only the small auxiliary battery.
Solution Approach 2:
The electrical system uses a composite battery configuration where two different batteries (primary 12V and auxiliary 24V) with different characteristics are combined to create a hybrid power source that leverages the strengths of each battery type for extended operation.
3Use of energy by moving object
If AC loads are used during Auto Stop events, then the fuel efficiency is improved, but the battery drain increases and engine restart is triggered sooner
Solution Approach 1:
The patent combines the charge capacity of both the primary and auxiliary batteries to create a larger effective energy reservoir. This allows the system to sustain AC loads during Auto Stop events for longer periods before the combined charge is depleted, delaying engine restart and maintaining fuel efficiency benefits.
Solution Approach 2:
The system dynamically changes the voltage parameter from 12V to 24V when AC loads are active, allowing higher power delivery from the same battery chemistry. This parameter change enables the system to support AC loads more efficiently without depleting battery charge as quickly.
4Device complexity
If the 12V DC bus is used to power the DC/AC inverter, then the system complexity is reduced, but the available power for AC loads is limited to about 400 Watts or less
Solution Approach 1:
The patent introduces asymmetry into the electrical system by adding a 24V auxiliary battery with different voltage characteristics than the standard 12V system. This asymmetric addition creates a dual-voltage architecture that can deliver higher power to AC loads while maintaining compatibility with the existing 12V infrastructure.
Solution Approach 2:
The patent adds a voltage dimension to the electrical system by introducing a 24V auxiliary battery in addition to the 12V system. This creates a two-dimensional voltage architecture (12V and 24V) that expands the power delivery capability while maintaining the original 12V bus structure for DC loads.
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 configuration provides more than three times the available power for AC loads during Auto Stop, enhancing fuel economy and supporting high surging loads, while maintaining the same battery size and cost as conventional designs.
Implementation Method 1
A second battery may be used to supplement the first battery and extend the duration of an Auto Stop event. The second battery is coupled between the 24V power net and ground.
Implementation Method 2
The alternator is driven by the engine and controlled by a voltage regulator that varies the alternator output to recharge the battery and maintain a desired voltage on a DC bus
Data Source
AI summary
A vehicle operates an internal combustion engine according to an automatic start-stop function to reduce fuel consumption. A first DC bus is adapted to connect to a plurality of DC loads. A primary battery is coupled between the first DC bus and a ground. A first alternator is driven by the internal combustion engine to supply electrical power to the first DC bus. A second DC bus is connected to a positive terminal of an auxiliary battery. A negative terminal of the auxiliary battery is connected to the first DC bus. A second alternator is driven by the internal combustion engine to supply electrical power to the second bus at a voltage corresponding to a sum of voltages of the primary and auxiliary batteries. An inverter receives electrical power from the second DC bus to generate an AC output adapted to connect to accessory AC loads.