System Definitions & Glossary

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

12V System Voltage Limits

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

24V

48V – the nominal voltage for a 48V system.

400V

800V

Battery Value Chain

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

Ancillary Services – the frequency regulation, reactive power and voltage-support services a grid operator will pay a BESS to provide, distinct from the revenue earned by simply buying and selling energy.

Anti-Islanding Protection – protection logic that detects when a section of grid has become electrically isolated from the wider network and forces connected inverters to disconnect, so a BESS doesn’t keep energising a line utility crews believe is dead.

Augmentation – the practice of topping up a BESS’s installed battery capacity partway through its contracted life, by adding fresh racks or swapping degraded modules, so the plant keeps hitting the power and energy figures it was contracted to deliver as the original cells fade.

Balance of Plant (BoP) – the collective term for everything on a BESS site that isn’t a battery rack or a PCS: transformers, switchgear, cabling, HVAC, fire systems, and the civil and structural work that ties it all together.

BCCM – Battery Charge Control Module sits between the Battery and the Charger.

Behind the Meter (BTM) – a type of energy storage system installed on the load side of the grid.

BEV – Battery Electric Vehicle

Black Start – the ability to energise a section of grid from a dead state with no external supply to synchronise to; a capability grid-forming BESS inverters can provide that conventional grid-following inverters can’t.

Capacity Market – a payment scheme, separate from energy sales, where a grid operator pays a BESS or any other generator simply for committing to be available to deliver power if called on, rather than for the electricity it actually ends up supplying.

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

Curtailment – the deliberate reduction of a BESS’s charge or discharge power below what it’s technically capable of, usually commanded by the grid operator to manage network constraints or an oversupply of renewable generation.

DC-Coupled / AC-Coupled – describes whether a BESS shares a DC bus and inverter with a co-located renewable generation source (DC-coupled) or connects to it only on the AC side through separate inverters (AC-coupled).

DC-DC

Grid Code – the country- or region-specific technical rulebook a grid operator imposes on every connected asset, spelling out how it must behave during disturbances, what reactive power it must be able to supply, and how its protection systems must be configured.

Grid-Following Inverter – an inverter that reads the voltage and frequency already present on the grid and matches its output to that signal; it needs a live grid to lock onto, so it can’t energise a network that’s down.

Grid-Forming Inverter – an inverter that sets its own voltage and frequency from an internal reference, rather than reading them off an existing grid signal, which is what lets it start up a dead section of network or run an islanded microgrid on its own.

E-Bus – buses fully or partially propelled by battery-powered electric motors.

Efficiency

E-LCV – light commercial vehicles, including vans and light-duty trucks, fully or partially propelled by battery-power electric motors.

Electric Motor

Energy Arbitrage – the practice of timing a BESS’s charge and discharge cycles around the daily swing in electricity prices, charging during cheap, low-demand hours and discharging during expensive, high-demand ones to capture the spread.

Energy Management System (EMS) – overarching management of the system and combination of sensors, components and battery packs. In a vehicle this can be a function that is part of the Vehicle Control System (VCS).

EREV – Extended Range Electric Vehicle is an electric vehicle with the addition of an internal combustion engine generator.

E-Truck – medium- and heavy-duty trucks fully or partially propelled by battery-powered electric motors.

EV – Electric Vehicle

FCEV – Fuel Cell Electric Vehicle

Front of the Meter (FTM) – a type of energy storage system installed on the utility or grid side.

HEV – Hybrid Electric Vehicle

High Voltage – in battery design this is anything above 60V.

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 Electric Vehicle (HEV) – Parallel Hybrid or Hybrid Electric Vehicle abbreviated HEV. Called the “Self-Charging Hybrid” by Toyota as the battery pack cannot be independently charged from a plug.

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.

Inverter – converts between DC and AC. DC being the battery pack and AC being a motor or grid. These units can be one-direction or bi-directional.

Long Duration Energy Storage (LDES) – a storage system that has a discharge duration of longer than 10 hours and can store energy for hours, days, weeks or even between seasons.

Low Voltage – DC system operating below 60V.

MCS – Megawatt Charging System (truck charging standard)

MHEV – Mild Hybrid Electric Vehicle

Microgrid – a local power generation and distribution system integrating distributed energy sources, storage devices, energy conversion equipment, loads, and monitoring and protection devices, etc., which is able to operate on and off grid.

Mild Hybrid Electric Vehicle (MHEV) – a hybrid electric vehicle where the electric system operates below 60V. This limits the amount of power that the system can deliver, but also significantly reduces the costs.

NACS – North American Charging Standard (SAE J3400)

NEV – new energy vehicles, including EV, hydrogen and other new type of fuel cell vehicles.

Nominal Voltage – cell or pack voltage at 50% State of Charge and at the declared discharge rate at which the capacity is given.

OEM – Original Equipment Manufacturer

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.

PHEV -Plug-in Hybrid Electric Vehicle

Plugin Hybrid Electric Vehicle (PHEV) – a hybrid electric vehicle where the battery pack has a significant capacity and allows the system to operate as an electric vehicle some of the time. Most notably the battery pack can be recharged from the grid, hence “Plug-In”.

Point of Common Coupling (PCC) – the physical connection point where a BESS plant’s equipment meets the public grid, and the reference point named in the connection agreement against which every grid code obligation — voltage limits, reactive power, ride-through — gets measured.

Power Conversion System (PCS) – the bidirectional power electronics block, container-mounted on most utility-scale projects, that converts the battery’s DC to grid-compliant AC on discharge and back again on charge, and that carries much of the grid-code compliance functionality.

Power Factor – the ratio of real power to apparent power delivered at the connection point; a BESS’s PCS can adjust it by controlling how much reactive power it exports or absorbs.

Power Plant Controller (PPC) – the plant-level control system that takes setpoints from the grid operator or EMS and turns them into coordinated commands for every PCS on site, so the whole plant presents a single, grid-code-compliant response rather than each inverter acting independently.

Rate of Change of Frequency (RoCoF) – electrical grid refers to how quickly the grid’s frequency is changing over time, typically measured in Hertz per second (Hz/s).

REEV / EREV – Range Extended Electric Vehicle is an electric vehicle with the addition of an internal combustion engine generator.

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.

Ride-Through (Voltage/Frequency) – a grid code obligation requiring a BESS to keep operating through a voltage or frequency dip or spike of defined severity and duration, instead of tripping offline and adding its own disconnection to whatever caused the disturbance in the first place.

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

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%.

Supervisory Control and Data Acquisition (SCADA) – the system giving site operators real-time visibility and manual control over a BESS’s equipment, distinct from the EMS, which handles the optimisation and automated dispatch logic layered on top.

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.

V2G – Vehicle to Grid

V2H – Vehicle to Home

V2L – Vehicle to Load

V2V – Vehicle to Vehicle

Wh – Watt hour