System Definitions & Glossary

Systems definitions & glossary covers everything else. This is definitely a work in progress…

12V battery system voltage limits

12V System Voltage Limits

High level overview of the automotive based 12V system voltage limits.





Battery Value Chain

The battery value chain looks at the whole eco system from mining the raw materials through to recycling.

Cold Climate EV Range

There are a number of factors that will impact the vehicle range and it is not totally due the battery as this is a two axis problem with the vehicle energy consumption also playing it’s part. Hence, let us break this into battery energy and vehicle energy consumption at the highest level and then list the factors under each.

  • Vehicle energy consumption
  • Battery energy



Electric Motor

High Voltage

High Voltage Interlock Loop (HVIL) – a low voltage signal loop that runs in parallel with and part of the HV connections, cables and components. Meaning that if the HV loop is broken the HVIL is also broken. Thus giving the ability to easily detect a disconnect in the HV system.

Hybrid System – a system that stores and uses energy in more than one form, eg a vehicle that has a petrol engine and an electric motor that can recover energy to store in a battery and reuse at a later time.


Low Voltage

Pack Metrics

A Pugh Matrix is a good way of making a high level comparison between applications and the key pack metrics.

In the case of mobile consumer products such as a mobile phone the lifetime of the battery is perhaps not as important as it would be in the case of a grid storage system. The mobile phone has a 2 to 3 year life before most are upgraded. A grid storage system needs 20 years of operation.

Road Vehicle Power Demand

Let’s look at the road vehicle power demand for the simple steady state condition. We will look at the tractive effort and power required:

  • Aerodynamic forces
  • Rolling resistance
  • Acceleration
  • Gradients
  • Hotel loads

Requirements – a list that the battery pack must be engineered to and deliver. This can include the targets, but also needs to include the legal requirements, functional requirements and features.

Round Trip Efficiency – the amount of energy delivered divided by the amount of energy input. This sometimes includes the conversion efficiency, eg Rimac quote their stationary storage system: AC round trip efficiency >92%.

Targets – a set of high level numbers that the battery pack needs to meet. Be careful to ensure that these are targets that the pack itself can be test against and are not part of the wider system. eg a battery pack can have a usable kWh target, but should not have a vehicle range target.

Wh – Watt hour

Watts are defined as 1 Watt = 1 Joule per second (1W = 1 Js-1)

time is simple 1 hour = 3600 seconds

Hence 1 Wh = 3600 Joules

So the Watt hour (Wh) is a strange unit as it is energy use per unit of time multiplied by time.

Wh/km – energy use for a vehicle.