Dynamic Alternator Voltage Control for Hybrid Battery Systems
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Solution Overview
Problem
Existing electric power supply systems for motor vehicles using both lead-acid and lithium-ion batteries face challenges in maximizing the lifespan of lead-acid batteries while minimizing fuel consumption, as they require high alternator voltage for simultaneous charging, leading to overconsumption of fuel and limited lithium battery performance.
Innovation Solution
A vehicle electrical power supply system with a controllable alternator and electronic management unit that imposes different setpoint voltages to prioritize charging of lead-acid batteries during start-up and lithium-ion batteries during driving, using a DC/DC transformer to manage voltage and extend the lifespan of both batteries while reducing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant high alternator voltage is used to simultaneously charge both lead-acid and lithium-ion batteries, then both batteries can be charged, but fuel consumption increases excessively
Solution Approach 1:
The alternator voltage is made dynamic rather than constant. The control unit switches between a first voltage level (higher than lead-acid battery voltage but lower than lithium-ion battery voltage) and a second voltage level (higher than both battery voltages). This dynamic adjustment allows the system to charge only the lead-acid battery during normal operation, reducing fuel consumption, and switch to charging both batteries when needed
Solution Approach 2:
The charging process is divided into periodic phases. During normal driving, the alternator operates at the first voltage level to charge the lead-acid battery. During specific periods (deceleration phases, parking modes, or when lithium battery charge drops below threshold), the system switches to the second voltage level to charge the lithium-ion battery, creating a periodic charging pattern that optimizes fuel consumption
2Duration of action of stationary object
If the maximum no-load voltage of the lithium battery is kept close to the lead-acid battery to enable preferential discharging, then the lead-acid battery lifespan increases, but the lithium battery energy capacity is limited
Solution Approach 1:
The system dynamically adjusts the alternator voltage based on the type of battery being charged. When charging the lead-acid battery, the alternator voltage is set to the first level (just above lead-acid voltage). When charging the lithium-ion battery, the voltage is increased to the second level (above both battery voltages). This allows the lithium battery to accept higher voltages and thus store more energy without compromising lead-acid battery lifespan during its preferred operating conditions
Solution Approach 2:
The alternator voltage parameter is changed between two distinct levels depending on which battery requires charging. The first voltage level preserves lead-acid battery lifespan by keeping it just above the battery's no-load voltage. The second voltage level enables efficient lithium-ion battery charging by exceeding both battery voltages. This parameter switching resolves the contradiction between battery lifespan and energy capacity
3Reliability
If the alternator voltage is set above the lithium battery voltage to enable lithium battery charging, then lithium battery performance improves, but lead-acid battery undergoes excessive charge-discharge cycles
Solution Approach 1:
The alternator voltage is dynamically controlled to be above the lithium-ion battery voltage only when necessary for lithium battery charging (during deceleration phases, parking modes, or when lithium charge drops below threshold). During normal driving phases, the voltage is maintained at the first level (above lead-acid but below lithium voltage), allowing the lead-acid battery to remain in a stable charged state without excessive cycling. This dynamic control preserves lead-acid battery cycle life while enabling lithium battery performance optimization
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 system effectively extends the lifespan of lead-acid batteries, reduces average fuel consumption, and optimizes lithium battery performance by strategically managing voltage levels and charging phases.
Implementation Method 1
a controllable alternator connected to the network, and capable of delivering to the second battery electrical energy under a controllable setpoint voltage at different setpoint values
Implementation Method 2
The system further comprises a DC/DC type voltage transformer capable of lowering the voltage delivered by the second battery to the network
Data Source
Figure 1~2
Figure 3
AI summary
A system for supplying electrical power to a vehicle comprises: - a network of electricity consuming units, which is able to be powered in a range of voltages less than or equal to a maximum network voltage (Vmax_network), - a first electrical accumulation battery connected to the network, and exhibiting a first maximum voltage when unloaded (V0max_Batt1) which is less than the maximum network voltage (Vmax_network), - a second electrical accumulation battery connected to the network, exhibiting a second maximum voltage when unloaded (V0max_Batt2), which is greater than the maximum voltage when unloaded of the first battery (V0max_Batt1), and a minimum acceptable voltage when unloaded (V0mini_Batt2) which is below the maximum network voltage (Vmax_network), - a drivable alternator connected to the network, and able to deliver to the second battery an electrical energy under a setpoint voltage drivable to various setpoint values (Valt_low, Valt_high). The system furthermore comprises an electronic management facility, configured to impose at least two different setpoint voltages successively on the alternator when the vehicle is running, namely a low alternator voltage (Valt_low) which is strictly greater than the first maximum voltage when unloaded of the first battery (V0max_Batt1), and a high alternator voltage (Valt_high) which is strictly greater both than the minimum voltage when unloaded of the second battery (V0mini_Batt2), and than the low alternator voltage (Valt_low).