technology
How Energy Storage Works
Reliable energy does not just happen. It must be stored, managed, and delivered when it matters most. Battery energy storage systems help keep electricity available when people need it, supporting renewable energy, strengthening the grid, and improving energy resilience. This simple guide explains lithium iron phosphate (LFP) battery technology and how a single battery cell becomes a complete battery energy storage system.
What is a Grid-scale Battery Energy Storage System (BESS)?
A battery energy storage system, often shortened to BESS, stores and releases electricity when it is needed—improving grid reliability or lowering the cost of generating and delivering electricity.
“Grid-scale” refers to larger systems—measured in megawatt-hours (MWh) or even gigawatt-hours (GWh)—that are installed directly on the power grid by utilities and independent power producers, rather than connected directly to homes and offices.
The battery system charges when electricity is abundant, then delivers that energy back to the power grid when demand rises or grid stability requires it. Battery systems are installed independently or integrate with energy generation – including natural gas, solar energy, and even nuclear energy - to reduce peak demand, improve grid reliability, and provide backup power for critical infrastructure.
Every system starts with the battery cell. Many grid-scale energy storage systems use lithium iron phosphate (LFP) because it offers excellent safety, long operating life, and dependable performance.
1 Cell
The basic building block of a battery system
4 Layers
Cell, module, pack, and DC block
Thousands
Of cells can work together in one BESS system
What Does “LFP” Actually Mean?
LFP stands for lithium iron phosphate, the material used in the battery’s positive electrode (called the cathode).
This chemistry is known for its safety, long lifespan, and reliable performance, making it well suited for grid-scale energy storage.
A Stable Structure
Iron and phosphate form a stable structure that performs reliably through thousands of charge and discharge cycles and across a wide range of operating temperatures.
Designed for Safety
LFP’s exceptional thermal stability makes it one of the safest lithium-ion battery chemistries for large energy storage projects located near communities, businesses, and critical infrastructure.
Abundant Materials
LFP relies on abundant iron and phosphate, reducing dependence on constrained raw materials.
INSIDE A PRISMATIC LFP CELL
A prismatic LFP cell uses a rigid, rectangular enclosure that allows cells to be arranged efficiently within a module or pack.
Each cell includes:
- Cathode: Lithium iron phosphate defines the chemistry of the cell.
- Anode: Stores lithium ions when the battery charges.
- Separator: Physically isolates the cathode and anode.
- Electrolyte: Allows lithium ions (electrical current) to move through the cell.
- Safety Vent: Helps manage pressure inside the enclosure.
One cell stores a limited amount of energy. Combined and managed at scale, thousands of cells power complete energy storage systems.
Five Reasons LFP Is Built for the power grid
Grid storage is not about fitting the most energy into the smallest space. It is about delivering safe, reliable power over years of operation.
01
Safer by Design
LFP withstands high temperatures and does not release oxygen during failure. That gives large systems a wide safety margin.
02
Longer Service Life
High-quality LFP cells can often deliver 4,000 to 6,000+ full charge cycles before reaching 80% of their original capacity, roughly twice the cycle life of NMC, a competing chemistry. At one cycle per day, that’s well over a decade of operation.
03
Lower Lifetime Cost
LFP’s long service life, use of abundant raw materials and reduced cooling requirements decrease the total cost of owning and operating an energy storage system over its lifetime.
04
Built for Daily Cycling
Most grid storage systems discharge for two to four hours, a strong fit for LFP. Its stable voltage supports accurate monitoring giving battery operators more accurate control over charging and discharging.
05
Trusted by Investors
Years of successful field deployments have made LFP one of the most trusted battery chemistries for utility-scale energy storage projects, helping developers more easily secure financing and insurance.
From Cell to Block: How Energy Storage Scales
A battery energy storage system is not one large battery. It is built in layers, with each layer adding capacity, monitoring, control, and protection.
cell
The basic unit that stores and releases electrical energy.
pack
A group of cells connected within a structured frame with monitoring and electrical protection.
DC Block
Battery packs integrated into a container with cooling, controls, monitoring, and safety systems.
Energy storage systems are often built one layer at a time. Cell-level quality is foundational to the performance, safety, and reliability of the packs, DC blocks, and systems build with them.
What a BESS Looks Like in the Field
A battery is only one part of a complete energy storage system.
Power electronics, cooling equipment, controls, monitoring software, and safety systems all work together to move energy safely between the batteries and the power grid.
1. power GRID
The electricity network that carries electricity from where it’s generated to where it’s used, including the connection point for the battery system.
2. transformer
Adjusts voltage for safe connection to the grid.
3. energy management system (Ems)
Decides when the battery should charge or discharge based on electricity demand, paired generation, energy prices, and electricity grid signals.
4. PCS or Inverter
Converts Direct Current (DC) ↔ Alternating Current (AC)
5. battery containers & battery management system (bms)
The battery containers hold the cells, modules, packs, cooling equipment, and safety systems. Inside the container, the battery management system (BMS) continuously monitors the batteries, balance performance, and resolve safety issues before they become problems..
What Shapes the Value of a Battery System?
Battery capacity is only part of the story. Long-term value comes from how safely, efficiently, and reliably a system performs year after year.
From cell to system, every layer matters.
Cells Set the Foundation
Cell quality and consistency shape performance at every level.
Cycle Life Matters
More charge and discharge cycle capability support a longer operating life.
Efficiency Adds Up
Higher efficiency returns more of the energy store and lower cost of ownership.
The Application Matters
The system must fit the application, including grid support, load and generation smoothing, demand management, and backup power.
Where FIXX Energy Fits
FIXX Energy manufactures American-made LFP prismatic battery cells and delivers energy storage solutions for utilities, data centers, and critical infrastructure.
From our 505,000 square foot facility in Smyrna, Tennessee, more than 500 employees build on over 14 years of battery manufacturing experience.
We believe every great energy storage system starts with a great battery cell. That’s why we focus on disciplined manufacturing, rigorous quality standards, and proven engineering, building the foundation for a stronger, more resilient electric grid.
LFP ESS cells produced
Sq Ft of production floor
#1
First U.S. LFP ESS facility
