Continuous Current Rating

Continuous power versus battery nominal voltage graph

At some point in the development of a battery pack design you need to consider the continuous current rating. Do this for charge and discharge as this then gives you one for the fundamental requirements to determine: Plotting continuous power versus system nominal voltage it is possible to see the voltage/power/current design points. Typically electric … Read more

Contactor Mass

Schaltbau contactors

For many applications contactor mass doesn’t matter, but for aviation every gram counts and hence we wanted to look for a trend. Contactor mass plotted versus continuous current rating. Not very much data with just 23 parts, but it appears that we are seeing distinct masses based on frame size. Hence a relationship to continuous … Read more

Contactor Faults

contactor schematic

Contactors are the only moving part in a battery pack and although simple there are a number of contactor faults that will stop the operation of the battery pack. Introduction to Contactors There are two main types of contactors: Normally Open (NO) and Normally Closed (NC). A NO contactor does not allow current to flow … Read more

A System Engineer’s Thoughts on Contactor Control

Schaltbau contactors

As a vehicle level systems engineer who spent many years working with an HV battery team, I naturally have some thoughts about opening and closing contactors. Here is my starter for 10 on the topic of ‘Control contactors’ 😇 Contactor Control is another one of those areas where responsibility is divided between a vehicle’s system … 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

Electrical System of Battery

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. Busbars are electrically conductive materials that maintain current flow from the cells to the external electrical loads. Aluminum and copper are … Read more