Methods and systems are provided for transporting and hydrating a redox flow battery system with a portable field hydration system. In one example, the redox flow battery system may be hydrated with the portable field hydration system in a dry state, in the absence of liquids. In this way, a redox flow battery system may be assembled and transported from a battery manufacturing facility to an end-use location off-site while the redox flow battery system is in the dry state, thereby reducing shipping costs, design complexities, as well as logistical and environmental concerns.

Means for maintaining level complementary electrolytes inflow battery tanks has first and second interconnected tanks 2, 3. The first tank 2 contains positive electrolyte, 2b, and the second tank containing negative electrolyte 3b. Both tanks have a void 2a and 3 a respectively, for air or other noble gases. The tanks themselves are connected by pipes; a lower tank connecting pipe 4, an upper tank connection pipe 5 with an inter-pipe connecting pipe 6 therebetween. The peak of the lower tank connection pipe 4a is designed to remain below the normal liquid level 7 of both tanks, in contrast to the upper tank connection pipe 5 which remains above the desired liquid level 7.

At a position between a fuel offgas inlet portion and a fuel gas inlet portion in a main body portion in the facing direction where a first end faces a second end, a fluid confluence joint is provided with at least either one of (i) at least one step formed over a whole circumference of an inner wall of the main body portion by reducing the passage sectional area on a fuel gas passage portion side to be smaller than the passage sectional area on a confluence passage portion side, and (ii) at least one partition wall formed over the whole circumference so as to project inwardly from the inner wall of the main body portion.

A modular fuel cell subsystem includes multiple rows of modules, where each row comprises a plurality of fuel cell power modules and a power conditioning module containing a DC to AC inverter electrically connected the power modules. In some embodiments, a single gas and water distribution module is fluidly connected to multiple rows of power modules, and a single mini power distribution module is electrically connected to each of the power conditioning module in each row of modules. In some embodiments, each row of modules further includes a fuel processing module located on an opposite side of the plurality of fuel cell power modules from the power conditioning module. Fuel and water connections may enter each row from the side of the row containing the fuel processing module, and electrical connections may enter each row from the side of the row containing the power conditioning module.

A method of refreshing an asymmetric redox flow battery system is described. The redox flow battery system comprises: at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor and having a volume; the negative electrolyte comprising water and the metal precursor and having a volume; the negative electrolyte having a concentration of the metal precursor greater than a concentration of the metal precursor in the positive electrolyte. The flow of mixed electrolyte past the negative electrode is prevented, and the negative electrolyte and positive electrolyte are mixed together. The mixed solution is reapportioned to the negative and positive sides based on the initial negative and positive electrolyte volumes. Flow of the refreshed negative electrolyte past the negative electrode is then resumed.

A method of refreshing an asymmetric redox flow battery system is described. The redox flow battery system comprises: at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor and having a volume; the negative electrolyte comprising water and the metal precursor and having a volume; the negative electrolyte having a concentration of the metal precursor greater than a concentration of the metal precursor in the positive electrolyte. The flow of mixed electrolyte past the negative electrode is prevented, and the negative electrolyte and positive electrolyte are mixed together. The mixed solution is reapportioned to the negative and positive sides based on the initial negative and positive electrolyte volumes. Flow of the refreshed negative electrolyte past the negative electrode is then resumed.

A flow battery comprising: a first tank having a variable internal volume and containing a first ionic solution having a first oxidation state, and wherein the first tank is substantially evacuated of any gas; a second tank having a variable internal volume and containing a second ionic solution having a second oxidation state that is different from the first oxidation state, and wherein the second tank is substantially evacuated of any gas; a reaction chamber operatively coupled with the first and second tanks such that the first ionic solution within the reaction chamber is separated from the second ionic solution by an ion exchange membrane; a first pump configured to pump the first ionic solution through the reaction chamber; and a second pump configured to pump the second ionic solution through the reaction chamber.

A flow battery comprising: a first tank having a variable internal volume and containing a first ionic solution having a first oxidation state, and wherein the first tank is substantially evacuated of any gas; a second tank having a variable internal volume and containing a second ionic solution having a second oxidation state that is different from the first oxidation state, and wherein the second tank is substantially evacuated of any gas; a reaction chamber operatively coupled with the first and second tanks such that the first ionic solution within the reaction chamber is separated from the second ionic solution by an ion exchange membrane; a first pump configured to pump the first ionic solution through the reaction chamber; and a second pump configured to pump the second ionic solution through the reaction chamber.

Methods to improve redox flow battery performance with improved CE, reduced electrolyte solution crossover, and simplified solution refreshing process have been developed. The methods include controlling the pre-charging degree and conditions to allow high quality metal plating (ductile and uniform), for example, Fe(0), on the negative electrode. Control of the pre-charging conditions can be combined with increasing the concentration of metal ions compared to existing systems, while maintaining the same concentration in both the negative and positive electrolytes, or increasing the concentration of metal ions in the negative electrolyte so that the negative electrolyte has a higher concentration of metal ions than the positive electrolyte.

An electrode assembly for a flow battery is disclosed comprising a porous electrode material, a frame surrounding the porous electrode material, at least a distributor tube embedded in the porous electrode material having an inlet for supplying electrolyte to the porous electrode material and at least another distributor tube embedded in the porous electrode material having an outlet for discharging electrolyte out of the porous material. The walls of the distributor tubes are preferably provided with holes or pores for allowing a uniform distribution of the electrolyte within the electrode material. The distributor tubes provide the required electrolyte flow path length within the electrode material to minimize shunt current flowing between the flow cells in the battery stack.