Right, from the one study I can find, commercial flow batteries have about 10-20x the internal resistance of a lithium ion battery, so the match the power and energy capabilities of a single li-ion cell you would need a liter of electrolyte and about 30 (!) cells (3 for voltage x 10 for power).
And that is for a commercial quality flow battery. And lithium ion batteries are wholesale in the $2 a piece range.
I'm not trying to say flow batteries are stupid or dumb, but their use cases are going to be very limited without some huge breakthroughs that will probably dramatically increase the complexity too.
On top of that, you don't have to match the internal resistance to match power. If you have plenty of material to absorb the heat, then you can tolerate more percentage points of loss.
In particular, while lithium ion batteries can be built to sacrifice discharge rate for a bit of extra capacity, something like a 3C discharge rate is easy enough to reach. And if your use case is powering a building for several hours, you might only need a .2C discharge rate. That would mean lithium ion as a technology is 15x overqualified, and a flow battery that gives you 10x less power would still be overqualified.
Many elements of being the "best choice" are thresholds. Excess performance doesn't make it better. Price is extremely important, but power density is not so important for most use cases. So if it's even slightly cheaper, expect to see a lot of it.
Christmas present for a battery enthusiast? :D
I think the argument against that is that we've spent tens of thousands of person-hours a millions of dollars more researching, developing, improving, and refining lithium-ion batteries than we have flow-batteries, and the purpose of the project in OP is to make it easier to tinker with flow-batteries.
Think of how much better lithium-ion batteries have gotten since we first started using them. We went from "You simply cannot achieve the energy density to propel (tethered) cars without fossil fuels" to "Oh wait we have electric cars now." in like a decade, and in the decade since them, lithium ion batteries have improved in every metric by at least an order of magnitude. We simply don't know how good flow-batteries can get, because we haven't tried, and it's silly to say "why bother trying, they're not very good right now" when we've just seen how much of a difference it makes to invest into this sort of technology.
Start taking GWh of storage and lithium ion technology gets really expensive and has a lot of associated risks. Flow batteries on the other hand don’t need to worry about a single cell failure resulting in a fire which then spreads.
While they both need to scale the amount of DC<>AC inverters based on peak power demand. If you want to discharge over 16 hours you’re using 2% of lithium ion’s peak power output and need a huge mess of wiring to move power from each internal cell to that inverter + complex battery packs with individual electronics cooling etc.
Flow batteries on the other hand can use a single pump (+ redundancy) and fat pipe to supply a huge array of ion-exchange membranes which then sit next to the inverters.
I'll take a basement (or garage) with a flow battery over lithium ion ANY day of the week if I want battery backup for my house.
At some point I expect we will look back at the era when we used really flammable electrolytes and laugh about how wild that was. I bet we are not that far from it being just a memory.
The largest use case is going to be grid scale storage, and for that one a bunch of dumb tanks and a bank of cells are far easier to handle and less risky than a bunch of li-ion cells that can go into runaway for whatever reason.
Flow batteries are cool because the storage element is extremely easy to scale. But its not even that great because you also need to scale the amount of cells dramatically to make it useful outside of edge cases. At which point it probably makes more sense to just use another storage mechanism.
So that's something. Learning how to build one from scratch seems worthwhile, much like learning to build a radio from scratch
