I am wanting to build a small scale Redox flow battery as a fun project. I know there is a list of flow batteries right now and I am trying to decide on one where the elements used are economical as well as one where the watt density is reasonably high. At least twice lead acid anyway. Issues arise in that electrolyte compositions are a little scarce on the net. It seems one design is using a VCl or VBr solution along with possibly a 4-5M solution of H2SO4. To be right honest, some of this stuff it literally blowing the dust off some old school books. I am trying to determine the elemental volumes. I think Bromine is actually pretty expensive. I would probably look to make one in 5gal bucks. Obviously the fuel cell or reactor will be the tedious part. Very interested to see one of these work. I am certainly open to other varieties using different electrolytes.