# Flow batteries

Batteries that keep their energy in liquid electrolytes in tanks, so capacity scales with tank size.

Source page: https://www.materialinsights.org/energy/e_flow_batt/

Storage · Electrochemical · No. 74

- Storage
- Duration: Hours to days
 Storage · Electrochemical · Foundation · Energy

A battery you enlarge by adding tanks: China's biggest stores 1,000 MWh in liquid vanadium that barely wears out.

Chart: Illustration: Flow batteries

##### Where it comes from

Chart: Map of where it comes from

Two tanks of dissolved vanadium are pumped past a membrane where they swap electrons; the liquid does not crack or swell, so it lasts about 10,000 cycles.

##### Three things to know

1. Because power and energy are sized separately, extra hours mean only more liquid and tanks, which suits 6 to 12 hour storage.
2. Only 70 to 80% of the electricity comes back out, against about 85 to 90% for lithium-ion.
3. Suppliers outside China are fragile: US firm ESS Inc lost USD 63.4 million in FY2025 and Australia's Redflow failed in 2024.

##### The journey

1. 1 **Vanadium ore**Mostly mined in China and Russia
2. 2 **Electrolyte**Vanadium dissolved in sulphuric acid
3. 3 **Tanks**Bigger tanks give more hours of storage
4. 4 **Cell stack**Pumped liquids swap electrons across a membrane
5. 5 **Grid**Carries solar through evening and night
 Covered in [Storing energy: from fuel stocks to batteriesEnergy](https://www.materialinsights.org/learn/energy/storing-energy/)

##### Go deeper pick a tab to open it in full

## Other sections

- [Overview](https://www.materialinsights.org/energy/e_flow_batt/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_flow_batt/correlation/index.md)
- [Science and technology](https://www.materialinsights.org/energy/e_flow_batt/sg-sci/index.md)
- [Engineering and performance](https://www.materialinsights.org/energy/e_flow_batt/sg-eng/index.md)
- [Economics](https://www.materialinsights.org/energy/e_flow_batt/sg-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_flow_batt/sg-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_flow_batt/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_flow_batt/links/index.md)