Continuous Current Rating

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

Aluminium Busbar Products

aluminium busbars as used on a battery module

for Cell Contacting Systems and Busbars Aluminium busbar products are used in manifold applications in batteries and battery systems due to their favourable structural, physical, and chemical properties. When it comes to cell contacting systems and busbars, electrical (and thermal) conductivity are decisive for balancing component resistance and cross-section to meet the designed space. However, … Read more

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

Internal Resistance 101

electrical symbol showing single cell and internal resistance

Let’s take a tiny step and understand how IR is measured in the first place. How are resistances measured? A small current is injected into the component and voltage is measured across it and then resistance is calculated by R=V/I; yes! This is how a multimeter does its’ job; it’s not rocket science. There are … Read more