# Vanadium Redox Batteries



## Hollie Maea (Dec 9, 2009)

Ertike said:


> I am currently looking into this technology for our etrike project here in the Philippines. Does anyone one know more info about this, for example setting up a refueling station using this technology. here is an article.
> 
> The vanadium redox flow battery was developed by Professor Maria Skylass-Kazacos and her team at the University of New South Wales, Australia. It is a low cost, low environmental impact battery that has a superior deep cycling life and can be mechanically refuelled in minutes.
> The vanadium redox battery stores energy in a liquid electrolyte solution of vanadium pentoxide dissolved in sulphuric acid. The electrolyte can be charged or discharged by pumping it through the battery stack and either supplying electric power to the stack or taking power from the stack. It can also be recharged by having the spent electrolyte pumped out and a fresh charge of electrolyte pumped in.
> The spent electrolyte can then be recharged in another battery with electricity from the mains or from renewable energy sources. This raises the opportunity for the establishment of refuelling stations so that electric vehicles could exchange their electrolyte and then continue on their way with no more delay than if refuelling with petrol or diesel.


Biggest disadvantage with flow batteries is energy density. The very highest energy densities that have been achieved in laboratories with VRBs is 40 Wh/L. A bit of math shows that this really isn't going to cut it for electric vehicles until densities get higher: A small battery pack--one that will only get your 40 or 50 miles in a small car--might be about 10kWh. For such a pack you would require 250L of electrolyte (that's about 66 US gallons). And of course that doesn't include the size of the stack, which would have to be scaled up pretty big to get decent power output (power density and energy density are independent for flow batteries). So although the idea of being able to "fuel up" your EV is a pretty seductive idea for a lot of people, I think that most people would find that having to drain and then refill 66 gallons of "fuel" every 40 miles wouldn't be that great of an improvement over fast chargers. Plus the cars would be VERY heavy as well due to the low gravimetric energy density.

Flow batteries hold a lot of promise if they can get the densities up, but for now I think they are still stuck for stationary applications. The cycle life up in the 10s of thousands plus would be nice too though!


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## batterytang (Nov 17, 2011)

Hi ertike,

How about the cost of that kind of Lead acid battery? For e-bike you'd better take a li-ion battery pack.


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## mizlplix (May 1, 2011)

This form of ion exchange cell has been around since the mid 1950's. Where it uses acid to carry the Vanadium ions, it has no lead or other metals. It merely uses an ion exchange membrane to seperate the two liquids.

When exhausted, you suck them out and refill, or charge as normally done with any battery. That is relatively quick, their ONLY caveat.

They have a much lower energy density than Lithium, but more than Lead/acid. 

They are slightly lighter than lead acid types, but not by much.

Even NASA rejected them for use, citing high cost for the energy delivered. You must factor in the extra support hardware too.

Miz


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