Hybrid Vehicle PEC Charger System

The Challenge

Millbrook Revolutionary Engineering's customer required a Power Electronics Carrier (PEC) battery charger unit. A PEC is part of a vehicle hybrid system. A hybrid vehicle is engineered to be more fuel efficient than a conventional combustion vehicle. Hybrid systems are designed to provide fuel savings during acceleration and braking. Upon initial acceleration, the electric motor uses the power stored in the battery to assist the move of the vehicle. When the vehicle comes to a stop, the electric motor helps slow the vehicle and simultaneously charges the battery. This process reduces wear on the brakes.

The PEC is a collection of batteries, relays and other components with the capability to communicate via CAN protocol. These components insure proper interface and function within the Hybrid system. The PEC batteries are stored inside a warehouse after use on a vehicle. A battery charger system is needed to charge the batteries before being installed on another vehicle to provide optimum performance.

The requirements for the PEC charger were as follows:

  • Ability to charge up 350 VDC, 5 Amps until the state of charge reaches a specified percentage
  • Ability to send different control voltages (12 VDC or 24 VDC) to the relays based on a part lookup database
  • Ability to read and write to the PEC via CAN protocol.
  • Ability to store charge information into a database that can be easily backed up, restored, maintained, and loaded on another machine
  • Ability to scan the serial and model number barcode from the PEC to store into the database
  • Ability to show the charge steps in the automated test sequence.
  • Built-in safety interlocks to prevent output of high

The Solution

To accomplish this task, Millbrook Revolutionary Engineering designed a system using a standard computer combined with National Instruments hardware and LabVIEW for the software platform. The system serves as a central location for communication between various hardware, controls relays, and automates the test sequence. A power supply with Ethernet capability was integrated to allow remote control of the charge voltage and current to the PEC battery.

A Symbol alphanumeric barcode scanner was used to allow the operator to scan the serial and model barcode numbers. A database was created with Microsoft Excel, a standard spreadsheet software tool. Software and hardware features were added to comply with safety interlock requirements. An analog input sensor was added to the output of the high output voltage relay, which allows the system to detect voltages from the PEC battery and warn the user.

System Background

The main components of the PEC charger include the following: a computer, a barcode scanner, a high voltage power supply, and a UPS (Uninterruptible Power Supply). The power supply requires 240 VAC input and outputs up to 400 VDC and 10 Amps for battery charging.

Two cables are provided from the charger station to the PEC battery – a high voltage connector and a low voltage connector.

The PEC battery has two main connections and a service disconnect. One connection is for the high voltage connector and the other is for the low voltage connector. The high voltage connector provides charge voltage and current to the PEC battery. The low voltage connector is a harness that controls various relays, reads signals, transmits and receives CAN messages.

The service disconnect is a manual switch to ensure there is no voltage supplied from the battery.

Summary

Millbrook Revolutionary Engineering's PEC Charger system was built with flexibility – allowing the user to load different CAN databases, defining the messages to read and write, defining the system limits for faults, setting different battery charge voltage, current and state of charge, and manual troubleshooting.

With its flexibility, it can easily meet any battery charger specification. The software was designed to be modular and expandable.

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