Just for history's sake - an 8 MWhr vanadium flow battery has...

Just for history's sake - an 8 MWhr vanadium flow battery has been installed in a renewable energy park in China
http://www.energymatters.com.au/renewable-news/flow-battery-zhangbei-em5312/

The battery was supplied by be PrudentEnergy VRB Systems which bought the battery patents from VRB in 2009
http://www.pdenergy.com/intellectual-property.php

VRB in turn took the technology from Pinnacle who raced to develop the technology developed by Prof Maria Skyllas-Kazacos at the University of NSW

Prudent claims that its proton exchange membranes are rugged enough to operate in the real world. The temperature specs for the system suggest also that the vanadium electrolytes are also stable in solution.