Series Battery Charging Control for Heavy Vehicle Voltage Imbalance
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Solution Overview
Problem
In heavy vehicles, batteries connected in series exhibit voltage imbalances due to differing internal resistances, leading to uneven charging and reduced battery life, as conventional systems cannot independently adjust the supply voltage to fully charge the battery with higher internal resistance without overcharging the other.
Innovation Solution
A control system that intermittently charges vehicle batteries at a constant current rate by monitoring voltage differences and current derivatives between batteries, using smart alternators to adjust supply voltage and interrupt charging when necessary, ensuring balanced charging and extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the supply voltage to the battery with higher internal resistance is increased to charge it fully, then the charging completeness of the battery with higher internal resistance is improved, but the other battery becomes overcharged
Solution Approach 1:
The patent implements periodic charging action by intermittently connecting the series battery pair to the alternator through a control device. The charging process is divided into multiple charge-discharge cycles, where the batteries are charged for a predetermined time period and then disconnected. This periodic action allows the batteries to naturally equalize their voltages during discharge phases, preventing overcharging while ensuring the battery with higher internal resistance receives sufficient charge over time.
Solution Approach 2:
The patent applies dynamic charging control by adjusting the charging parameters based on the real-time state of the batteries. The control device monitors the voltage difference between batteries and dynamically adjusts the charging current and duration. The charging current is limited to a maximum value, and the charging time is predetermined based on the battery capacity and state of charge, creating a dynamic adaptation to the varying charging needs of the two batteries.
2Device complexity
If conventional constant voltage charging is used, then the charging system is simple, but voltage imbalances and uneven charging occur between batteries
Solution Approach 1:
The patent introduces periodic charging-discharge cycles to replace conventional continuous constant voltage charging. The control device connects the series battery pair to the alternator for a predetermined time period, then disconnects them. This periodic action creates natural voltage equalization during discharge phases, addressing the voltage imbalance problem without requiring complex voltage regulation circuits or individual battery management systems.
Solution Approach 2:
The patent enables the battery system to self-regulate voltage imbalances through controlled discharge phases. During the discharge period between charging cycles, the batteries naturally equalize their voltages based on their internal resistances and capacities. This self-service mechanism eliminates the need for active voltage balancing circuits or complex control algorithms, maintaining system simplicity while improving charging balance.
3Productivity
If the battery with lower internal resistance is charged at normal rate, then the overall charging efficiency is maintained, but the battery with lower internal resistance experiences increased fatigue due to more frequent charge-discharge cycles
Solution Approach 1:
The patent implements periodic charging with predetermined time periods that are optimized to balance charging efficiency and battery life. The charge period is set based on the battery capacity and the maximum allowable charging current, ensuring that the battery with lower internal resistance does not undergo excessive charge-discharge cycling. The periodic disconnection allows the system to maintain efficient charging while reducing the cumulative fatigue on the more robust battery.
Solution Approach 2:
The patent changes the charging parameters by limiting the maximum charging current and setting predetermined charging durations. Instead of using high current fast charging that would cause excessive cycling, the system uses controlled current levels and time-limited charging sessions. This parameter optimization ensures that the battery with lower internal resistance is charged efficiently without subjecting it to excessive stress, thereby extending its operational life.
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 approach reduces intrinsic imbalances between batteries, extends the life of the battery with lower internal resistance, and allows for efficient power distribution during vehicle operations.
Implementation Method 1
an electric generator is operated to charge the pair of batteries
Implementation Method 2
the two complete batteries, with all probability, have different dynamic behaviour. In other words, one of the two tends to charge less because it has a higher internal resistance
Data Source
Figure 1
Figure 2
AI summary
A charging system of a pair of batteries mutually connected in series of a heavy vehicle, the system comprising at least one alternator (G3) connected to a vehicle electrical power supply system, the pair of batteries (Bl, B2) being mutually connected in series (B1+B2) and to the vehicle electrical power supply system, monitoring means (S) for monitoring a charging voltage (Vtot) of the series of batteries (B1+B2), processing means (VCU, ECU) suitable for interfacing with the monitoring means (S) and configured to control the at least one alternator (G3) so as to vary a respective supply voltage, wherein the processing means (VCU, ECU) are configured to command the start of a charging process of the series of batteries (Bl + B2), when a difference between the respective voltages exceeds a first predefined threshold value and to command the interruption of said charging process when a derivative of a current absorbed by the series of batteries (Bl + B2 ) exceeds a second predefined negative threshold.