The confusion as one goes through TTax step by step/help/more and the IRS instructions is on the definitions of "battery storage" and "fuel cell". TTax and IRS fail to add the definition of fuel cell and the fact that batteries and fuel cells work very similar. Battery storage is self explanatory. For fuel cell, Form 5695 Instruction states " Qualified fuel cell property is an integrated system comprised of a fuel cell stack assembly and associated balance of plant components that converts a fuel into electricity using electrochemical means". Unfortunately there is no further definitions for "fuel cell", so I looked for the definition: "a device that generates electricity through an electrochemical reaction, not combustion." So a battery fits this definition, it does not use combustion, and works based on an electrochemical reaction (has a positive and negative pole AND a chemical between these, and it has a kW label). A battery fits BOTH definitions of battery and fuel cell.
One could argue the above with the IRS, but I kept looking for details details details, and found my answer at the Office of ENERGY EFFICIENCY & RENEWABLE ENERGY which I would recommend be added to TTAX at least under help or more. "Note: To qualify as a fuel cell, the cell does not run down or need recharging".
