Make your own mind up (from Wiki):
The main advantages of the vanadium redox battery are that it can offer almost unlimited energy capacity simply by using larger electrolyte storage tanks, it can be left completely discharged for long periods with no ill effects, if the electrolytes are accidentally mixed, the battery suffers no permanent damage, a single state of charge between the two electrolytes avoids the capacity degradation due to a single cell in non-flow batteries, the electrolyte is aqueous and inherently safe and non-flammable,
[16] and the generation 3 formulation using a mixed acid solution developed by the
Pacific Northwest National Laboratory operates at a high temperature allowing for passive cooling
[17]
The main disadvantages with vanadium redox technology are a relatively poor energy-to-volume ratio in comparison with standard
storage batteries (although the Generation 3 formulation has doubled the energy density
[17] of the system), and the aqueous electrolyte makes the battery heavy and therefore only useful for stationary applications.
