Battery Charge Controller for Vehicle Power Distribution
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Solution Overview
Problem
In tractor/trailer combinations, the crank battery is depleted by auxiliary loads when the engine is inactive, and liftgate batteries lack a charging system, leading to inefficient energy management and potential starting issues.
Innovation Solution
A battery charge controller manages electrical energy by monitoring voltage levels of the crank battery and onboard power sources, using comparators and switching devices to couple and decouple power sources to recharge auxiliary batteries, ensuring the crank battery remains above a threshold voltage for starting and using alternative power sources when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the crank battery supplies power to auxiliary loads when the engine is inactive, then the auxiliary loads can operate, but the crank battery voltage drops below the threshold needed for reliable starting
Solution Approach 1:
The electrical system is segmented into two separate batteries: the crank battery dedicated to starting operations and the auxiliary battery dedicated to powering auxiliary loads. This segmentation allows each battery to maintain its voltage within optimal ranges for its specific function, preventing the crank battery from being depleted by auxiliary loads while still enabling auxiliary operations when needed.
Solution Approach 2:
A battery charge controller is introduced as an intermediary device that manages power distribution between the crank battery, auxiliary battery, and alternator. The controller monitors voltage levels and automatically switches connections to ensure the crank battery is recharged from the alternator when available, and prevents auxiliary loads from depleting the crank battery below threshold levels.
2Device complexity
If the liftgate battery relies on power from the tractor or reefer unit without its own charging system, then the system complexity is reduced, but the liftgate battery cannot be recharged when disconnected from the tractor
Solution Approach 1:
The auxiliary battery serves multiple functions: it powers auxiliary loads when the engine is running, stores energy from the alternator when available, and can independently power the liftgate when disconnected from the tractor. This multi-functionality eliminates the need for separate charging systems while enabling independent operation.
Solution Approach 2:
The auxiliary battery acts as a self-service energy storage device that accumulates charge from the alternator during connected operation and autonomously provides power during disconnected operation. This self-service capability allows the liftgate to operate independently without requiring a separate charging system or constant connection to the tractor.
3Reliability
If the crank battery is continuously monitored and protected from discharge, then the starting reliability is maintained, but the auxiliary loads cannot operate when the engine is inactive
Solution Approach 1:
The electrical system is divided into two independent power sources: the crank battery reserved for starting and the auxiliary battery for auxiliary loads. This segmentation resolves the contradiction by allowing auxiliary loads to draw power from the auxiliary battery without affecting the crank battery's charge level, while still maintaining starting reliability.
Solution Approach 2:
The battery charge controller serves as an intermediary that manages power flow between the two batteries and the alternator. It enables auxiliary loads to operate on the auxiliary battery when the engine is off, while simultaneously managing the recharging of the crank battery from the alternator when the engine is running, thus maintaining both starting reliability and auxiliary operation capability.
Data Source
AI summary
A vehicle incorporates a crank battery, a rechargeable auxiliary battery, and an onboard electrical power source separate from the crank battery and the auxiliary battery. A battery charge controller manages a supply of electrical energy to the auxiliary battery to charge the auxiliary battery. The battery charge controller includes a first comparator for monitoring a voltage level of the crank battery, and a second comparator for monitoring a voltage level of the onboard electrical power source. A first switching device electrically couples the crank battery and the auxiliary battery to charge the auxiliary battery when the voltage level of the crank battery exceeds a first voltage threshold, and electrically decouples the crank battery and the auxiliary battery when the voltage level of the crank battery is below the first voltage threshold. A second switching device electrically couples the onboard power source and the auxiliary battery to charge the auxiliary battery when: (i) the voltage level of the crank battery is below the first voltage threshold and (ii) the voltage level of the onboard power source exceeds a second voltage threshold; and electrically decouples the onboard power source and the auxiliary battery when the voltage level of the onboard power source is below the second voltage threshold.