TRU Battery Charger Offset Current Compensation for Accurate Charging
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Solution Overview
Problem
Transport refrigeration unit (TRU) battery chargers face inaccuracies in output current due to dynamically changing loads, leading to potential battery depletion and failure to restart under certain conditions, as they do not account for offset currents drawn during null-mode voltage measurements.
Innovation Solution
A system and method that dynamically characterizes the load connected to the TRU battery charger by measuring and communicating the offset current through a programmable TRS Controller, allowing the charger to adjust its output current and transition between charging modes accurately, using a CAN interface for real-time data communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the TRU battery charger uses a fixed charging algorithm without dynamic load characterization, then the device complexity is reduced, but the charging accuracy and reliability deteriorate due to unaccounted offset currents
Solution Approach 1:
The system implements feedback by measuring the actual offset current drawn during null-mode voltage measurements and using this measured value to dynamically adjust the charging algorithm. The TRS Controller continuously monitors offset current and communicates this information to the battery charger, enabling real-time compensation and maintaining charging accuracy under varying load conditions.
Solution Approach 2:
The system performs self-characterization by having the TRS Controller measure its own offset current consumption during normal operation. The controller essentially characterizes itself as a load, eliminating the need for external characterization equipment or complex separate testing procedures, thereby reducing overall system complexity while maintaining measurement precision.
2Reliability
If the TRU battery charger does not dynamically characterize load conditions, then the ease of operation is maintained, but the reliability deteriorates due to potential battery depletion and failure to restart
Solution Approach 1:
The system uses feedback from offset current measurements to dynamically adjust charging parameters and transition between charging modes (bulk, absorption, float). This ensures the battery is charged accurately under all operating conditions, preventing depletion and ensuring reliable restart capability without requiring user intervention or complex manual adjustments.
Solution Approach 2:
The charging system transitions from a static fixed algorithm to a dynamic adaptive algorithm that automatically adjusts charging current based on real-time offset current measurements. The system dynamically characterizes load conditions and modifies charging behavior accordingly, improving reliability while maintaining ease of operation through automated adaptation.
3Productivity
If the TRU battery charger operates without offset current compensation, then the loss of time is reduced, but the productivity deteriorates due to inefficient charging and potential battery depletion
Solution Approach 1:
The system continuously monitors offset current and uses this feedback to optimize charging efficiency by adjusting the charging current to match actual load conditions. This prevents energy waste from overcharging or undercharging, improving overall charging productivity while the automated nature of the system eliminates additional time loss through seamless operation.
Solution Approach 2:
The system changes charging parameters (current, voltage, charging mode) based on measured offset current values. By dynamically adjusting these parameters to match actual system conditions, the system maximizes charging efficiency and productivity without requiring manual intervention or causing time loss through operational disruptions.
Data Source
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 IRS 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.