A Flow Battery is made up of a water based liquid (Zinc Bromide) that flows between two tanks. When the battery is charged the Zinc is extracted from the liquid, when the battery is discharging the Zinc is put back into the liquid.
One of the core advantages that flow batteries have over Lithium-ion and Lead Acid Batteries is that they have a 100% depth of discharge (DoD), meaning that the battery can be completely discharged with no negative effects on the battery performance or lifespan. Flow batteries can also be kept on the shelf at zero charge without degrading, most other batteries need to be kept at a minimum charge level.
There are a number of other advantages that flow batteries offer:
- They can tolerate extreme weather conditions, up to 50°C
- The Zinc-Bromide inside the battery is a fire retardant
- There is no chance of explosion due to the physical separation of the different components
- Flow Batteries are cheaper to refurbish due to their simple construction
A disadvantage of the Flow Battery is their life cycle compared to some of the high end Lithium-ion Batteries, they have a lifespan of around 4000 cycles at 100% DoD. They also need to be regularly discharged to 100% to ‘clean’ the internal electrodes.