Offset current implementation for battery charger
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Solution Overview
Problem
Transport refrigeration unit (TRU) battery chargers face inaccuracies in adjusting output current due to dynamically changing loads, leading to potential battery depletion and failure to restart under certain conditions, as existing systems do not account for offset currents drawn during null-mode voltage measurements.
Innovation Solution
A system and method that dynamically characterize the load connected to the TRU battery charger by measuring and communicating the offset current through a programmable TRS Controller, allowing the smart battery charger to adjust its output current and transition between charging modes accurately, using a CAN interface or other communication buses for real-time data exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery charger uses a fixed charging algorithm without offset current compensation, then the device complexity is reduced, but the charging accuracy and reliability deteriorate due to dynamically changing loads
Solution Approach 1:
The system continuously monitors offset current during null-mode voltage measurements and feeds this information back to the battery charger controller. The controller adjusts the charging algorithm in real-time based on the measured offset current, ensuring accurate charging despite dynamically changing loads. This feedback mechanism resolves the contradiction by maintaining high measurement precision without requiring overly complex hardware modifications.
Solution Approach 2:
The battery charger system performs self-characterization by measuring its own offset current during normal operation. The null-mode voltage measurement process inherently provides the opportunity to measure offset current without external intervention. This self-service approach improves charging accuracy while avoiding additional complex measurement devices.
2Reliability
If the battery charger dynamically adjusts output current based on offset current measurements, then the charging reliability is improved, but the device complexity increases due to additional measurements and communications
Solution Approach 1:
The existing null-mode voltage measurement functionality is made multi-functional by simultaneously measuring both battery voltage and offset current during the same operational phase. The single null-mode measurement process serves dual purposes: characterizing battery voltage levels and quantifying offset current. This universal approach improves charging reliability without adding separate measurement systems or increasing overall device complexity.
Solution Approach 2:
The system combines offset current measurement with the existing voltage measurement process by performing both measurements during the null-mode charging phase. The controller integrates both measurement functions into a single operational mode, eliminating the need for separate measurement circuits or additional communication protocols. This merging strategy enhances reliability while keeping the device architecture streamlined.
3Productivity
If the battery charger operates without dynamic load characterization, then the ease of operation is maintained, but the productivity decreases due to inefficient charging modes
Solution Approach 1:
The battery charger transitions from a static charging algorithm to a dynamic one that continuously adapts to changing load conditions. The controller adjusts charging parameters in real-time based on measured offset current, optimizing charging efficiency throughout the charging process. This dynamic approach improves productivity while maintaining ease of operation through automated adaptation without user intervention.
Solution Approach 2:
The system changes operational parameters (charging current, voltage thresholds) based on measured offset current values. The controller dynamically adjusts these parameters to match actual load conditions, maximizing charging efficiency. This parameter adaptation occurs automatically through the control algorithm, preserving ease of operation while significantly improving charging productivity.
Data Source
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AI summary
A transport refrigeration unit (TRU) battery charging system includes a programmable transport refrigeration system (TRS) Controller, a TRU battery and a programmable battery charger (BC) programmed to transfer electrical current to the TRU battery via a predetermined current path through the programmable TRS Controller in response to a value of offset current drawn from the TRU battery by the programmable TRS Controller and subsequently communicated to the programmable BC by the programmable TRS Controller. The programmable TRU battery charger allows for a dynamic load characterization of the programmable TRS Controller and accessory loads based on programmable TRU battery charger internal shunt current measurements and programmable TRS Controller internal shunt current measurements to allow the programmable TRU battery charger to function properly with all intended modes of operation.