## Maximum Cell Discharge Capability

Establishing the maximum cell discharge capability is difficult without understanding the design in detail. However, you can work towards establishing this limit with a number of measurements and calculations. The aim of this post is to describe that approach, the underlying physics, some of the measurements and calculations. First of all though we need to … Read more

## Auxiliary systems power consumption in electric vehicles

Auxiliary systems power consumption in a vehicle especially an electric vehicle have a big effect on the vehicle range. The Range is decided by the battery capacity in kWh. Battery capacity is primarily used to provide traction power through AC or DC motor. Efficiency of motor, drivetrain and battery can tell you how much power … Read more

## Parallel then Series or Series then Parallel

How should you connect battery cells together: Parallel then Series or Series then Parallel? What are the benefits and what are the issues with each approach? Series and Parallel The operating voltage of the pack is fundamentally determined by the cell chemistry and the number of cells joined in series. The ampere-hour capacity of the … Read more

## 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

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

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

## Control 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 of control contactors. Here is my starter for 10 on the topic of ‘Control contactors’ ðŸ˜‡ Contactor Control is another one of those areas where responsibility is divided between a … Read more

## Aluminium Busbar Products

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

## Optimal Busbar Joint Overlap

What is the optimal busbar joint overlap? It should be noted that the experimentally derived optimum is for plain busbars and does not include a hole for the fixture. Braunovic [3] shows the impact on resistance of the joint overlap. The resistance ratio is the ratio of the resistance measured across the joint divided by … 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