What is inside a stationary battery system?
The technician opens the container. Rows of racks, a cooling unit, an inverter cabinet, sensors in the ceiling.
It looks like a small data centre, but it stores energy.
The questionWhat does a stationary battery consist of?
Thousands of lithium-ion cells, grouped into modules and racks, often with LFP chemistry.
Select each part to see what it does.
Why LFP dominates
A does not have to be light. That favours cells: they store less energy per kilogram than , but cost less and contain no cobalt. The IEA notes that stationary storage predominantly uses LFP, and that LFP packs were on average more than 40% cheaper per kWh than NMC in 2025, partly because storage needs less energy density.
The chemistries are explained in eMobility and EV basics, stop 02.
A defined product in EU law
The EU Batteries Regulation defines a stationary battery energy storage system as an industrial battery with internal storage, designed to store energy from and deliver it to the grid, or to store and deliver it to end users. Since 18 August 2024, its must hold up-to-date data on and expected lifetime.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
Why do stationary batteries mostly use LFP cells?
Stationary systems trade weight for cost and lifetime; LFP fits that trade.
What does the inverter of a battery system do?
The BMS watches the cells, fire protection detects hazards, the controller decides; the inverter converts.
Since when must the BMS of stationary systems hold state-of-health data in the EU?
Article 14 of the Batteries Regulation applies from 18 August 2024.
- BMS Battery management system: the car's electronics that decide how much power the battery accepts at each moment. EV charging fundamentals, stop 04 Glossary
- LFP Lithium iron phosphate: a lithium-ion chemistry without cobalt, lower in cost, with less energy per kilogram than NMC. eMobility and EV basics, stop 02 Glossary
- NMC Nickel manganese cobalt: a lithium-ion chemistry that stores more energy per kilogram than LFP. eMobility and EV basics, stop 02 Glossary
- State of health How much energy the battery can hold today compared with when it was new, in percent. eMobility and EV basics, stop 08 Glossary
- Stationary battery energy storage system In EU law, an industrial battery with internal storage designed to store energy from and deliver it to the grid or to end users. Glossary
- IEA: Global EV Outlook 2026: Electric vehicle batteries. https://www.iea.org/reports/global-ev-outlook-2026/electric-vehicle-batteries. Checked 09 Oct 2026. Licence: CC BY 4.0.
- EUR-Lex: Regulation (EU) 2023/1542 on batteries, Articles 3, 12, 14 and 77 and Annex V. https://eur-lex.europa.eu/eli/reg/2023/1542/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.
- EUR-Lex: Regulation (EU) 2023/1542 on batteries, Articles 3, 12, 14 and 77 and Annex V. https://eur-lex.europa.eu/eli/reg/2023/1542/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.