Electrical Contact Resistance

The Electrical Contact Resistance at a metal to metal contact is primarily governed by: The surface structure can be further described by the surface flatness, surface oxidation and water adsorption. These joints in a battery pack will either be welded or bolted. Initially the easiest to think about is the bolted busbar joint. The bolt … Read more

Pre-Charge Resistor

When the battery pack contactors are closed onto a motor and inverter there will be an inrush of current into the inverter capacitor. This very high current is at a minimum likely to age the contactors, it could permanently damage the contactors. Therefore, when we closed the contactors on the battery pack we do this … Read more

How to select EV Contactors

contactor current rating vs time

Contactor selection is an iterative process that includes consideration of system specifications as well as failure scenarios. Most of the contactor manufacturers share necessary information in datasheets. Thus, a wise approach would be making a comparison table to cover basic specifications like thermal and mechanical initially. System Specifications After pre-selection based on datasheet values, we … Read more

Contactors: The Basics

contactor schematic

Contactors are electromechanical switches. They control the connection of battery Cells to the external electrical circuit. A contactor has an electromagnetic circuit. It simply works like a solenoid to push moving contact [1]. Therefore, contactors have two different electrical circuits inside: one is for actuation and the other one is to carry currents during the … Read more

Fuses: The Basics

fuse schematic

The basics of fuses are protection devices that protect electrical circuits against undesired high currents. We can use passive fuses and pyro fuses in battery design. Passive Fuse Passive fuses break the circuit only as a result of high currents for a certain time. They have a weak internal structure as a melting element. During … Read more