High Voltage System

The High Voltage system associated with a group of cells strung together in series and/or parallel.

HV schematic

The electrical design of the battery pack is associated with fundamental electrical elements. These elements are: Busbars, Contactors, Fuses, pre-charge resistors, current sensors, HV (High Voltage) and LV (Low Voltage) Connectors, and wiring harnesses.

This will cover:

  • Cell electrical interconnects
    • Welded, bolted, sprung and all forms of cell electrical connections
  • Module to module electrical power connections
  • Battery pack electrical connections
  • Distribution board
  • External connectors

For all of these components we need to consider:

  • Electrical resistance
  • Electrical isolation
  • Electrical rating
  • Connection electrical resistance
  • Self heating
  • Heat transmission
  • Creepage and Clearance
  • Mechanical integrity
  • Failure modes
  • Service and maintenance
  • Manufacturing requirements
  • Assembly requirements
  • Recycling

Busbars are the main electrical connections between cells, modules and connect all of the HV system to the outlet connector. Normally made from copper or aluminium. Careful consideration needs to be taken:

  • Cross-sectional area
  • Creepage and clearance
  • Thermal impact on other components
  • Joints between busbars
  • Contact resistance
  • Electrical isolation
  • Mechanical restraints
  • Expansion and contraction
  • Thermal runaway
  • Parasitic capacitance
  • Optimization for stamping

HV Battery Junction Box

The HV battery junction box brings together the measurement, control and connections of the battery high voltage (HV) system. Therefore, it would normally contain:

  • contactors
  • pre-charge resistor and contactors
  • fuses
  • current sensor
  • connectors

Short Circuit

By short circuit we mean an electrical short circuit, a very low resistance path between the positive and negative sides of the cell or cells. A short circuit can be inside a battery cell or external to a battery cell.