# Battery energy storage system

Canonical URL: https://eloragrid.ai/symbols/battery-energy-storage-system
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: BESS
Drawing use: SLD
Reference families: IEC, IEEE / ANSI, Manufacturer

A complete battery plant block combining batteries, power conversion and controls, shown as one source or sink on an SLD.

## In plain English

### What does Battery energy storage system mean?

A battery energy storage system is the full plant: battery racks, a bidirectional power conversion system, transformers, auxiliary supplies and a plant controller. On higher-level single-line diagrams it is shown as one block with a battery mark and a converter mark, connecting to the network through a breaker and often a step-up transformer.

### A simple example

The block is labelled with both power and energy ratings, for example MW and MWh, since the two together define how long the system can deliver rated output. More detailed drawings break the block down into racks, the conversion system and auxiliaries.

### What the drawings help you do

The symbol does not show usable energy after depth-of-discharge limits, degradation over life, or whether the converter is grid-forming. These figures, plus the auxiliary load which can be significant for cooling, come from the performance specification.

### This particular reference

A complete battery plant block combining batteries, power conversion and controls, shown as one source or sink on an single-line diagram. A BESS block is the complete plant; a battery symbol is only the electrochemical store.

### Terms

- Winding: A coil of conductor inside an electrical machine or transformer.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Battery energy storage and power conversion](https://www.eaton.com/sg/en-us/products/energy-storage.html)
- [xStorage battery energy storage system](https://www.eaton.com/us/en-us/catalog/energy-storage/xstorage-battery-energy-storage-system.html)


## What it represents

A battery energy storage system is the full plant: battery racks, a bidirectional power conversion system, transformers, auxiliary supplies and a plant controller. On higher-level single-line diagrams it is shown as one block with a battery mark and a converter mark, connecting to the network through a breaker and often a step-up transformer.
The block is labelled with both power and energy ratings, for example MW and MWh, since the two together define how long the system can deliver rated output. More detailed drawings break the block down into racks, the conversion system and auxiliaries.
The symbol does not show usable energy after depth-of-discharge limits, degradation over life, or whether the converter is grid-forming. These figures, plus the auxiliary load which can be significant for cooling, come from the performance specification.

## How to read it

- Always read both the power and energy ratings.
- Check whether the block includes its own step-up transformer.

## Information to show or reference

- State MW, MWh and point of connection voltage.
- Show breaker, transformer and auxiliary supply.
- Reference converter control mode.

## Important distinction

A BESS block is the complete plant; a battery symbol is only the electrochemical store.

## Facts

- Ratings: Power and energy
- Contents: Batteries, PCS, controls, auxiliaries
- Preview: Independent educational illustration; not a product outline

## Public references

- [Battery energy storage and power conversion](https://www.eaton.com/sg/en-us/products/energy-storage.html) — Eaton. Public battery energy storage and power conversion context.
- [xStorage battery energy storage system](https://www.eaton.com/us/en-us/catalog/energy-storage/xstorage-battery-energy-storage-system.html) — Eaton. Public battery storage system documentation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.