June 26, 2011
June 26, 2011
June 29, 2011
22.269.1 - 22.269.13
Automated Battery Charger Instrumentation Interface for Multiple Interconnected Battery Strings as a Student Project The US Navy operates an experimental quarter‐scale submarine to test new concepts in naval architecture. This submarine is an all‐electric ship, run by a six‐phase synchronous motor. Nominal operating voltage is 720V DC, supplied from seven parallel strings of sixty lead‐acid batteries each. These batteries must be charged, a process that takes about eight hours. The chargers are configured so that each charger supplies energy to one of the strings of batteries. The incumbent system required an operator to manually configure, start, monitor, and manage each of the chargers individually. Previous efforts to interface to the chargers’ internal digital interface had failed. The project assigned to a senior undergraduate design team was to investigate the digital interface and design a software configuration that would communicate with it. From there, the students were tasked to collect data from each charger, e.g., voltage, current, power, energy history, and temperature. Such data should be communicated to a desktop computer and displayed with a graphical user interface of the students’ design. This paper describes how the students successfully accomplished these goals. They found that the chargers’ interface board had multiple interface technologies, e.g., RS232, RS485, GPIB, etc. However, important components were missing from the boards and a means of multiplexing the signals from seven boards was lacking. They specified and bought the necessary parts, testing and proving the revised boards as capable of communicating through the available interfaces. Through and extensive search, they found a commercial board capable of interfacing that signals from the seven chargers with no translation or reformatting. They then set about programming their tasks on the interface and multiplexer boards. They collected data and communicated it to a data file on the computer. They sent commands to the interface board in a manner that caused appropriate actions, e.g., start, check system for safe and defined initial condition, change parameters to conform to a desired state, engage charging mode, stop charging, set or change current level, etc., The students designed a graphical user interface to show the state of the system and to enable changes conveniently. When the design was finished, they demonstrated it in a laboratory on campus. Successful performance enabled them to travel to the Navy base and install their boards on the chargers. On their first trip, they identified several interface issues not readily apparent in the laboratory. These will be discussed in the paper. On their second trip, their charger management system worked as specified. Details of the design will be presented in the paper.
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