We're building a lot of EVs right now. Pretty much any battery has hard to process material in it. Packs for vehicles last between 5-15 years, but there's still a lot of energy storage capacity left.
You reduce the amount of processing & mining needed AND make EVs more affordable if you can extend the life of the battery pack beyond just it's automotive application by giving it another life in grid storage.
Scale and immediacy. We already have some places in the world that have an overcapacity of renewables, but still suffer from outages due to the energy market. And if the current exponential trend continues, we will reach renewables overcapacity world wide by the mid 2030s. We essentially needed wide deployment of grid-scale batteries yesterday to offset decommissioned baseload and curtail the use of peakers that can charge through the nose when power drops. There's a strong market for a dirt cheap, dispatchable, deep cycling, and scalable battery chemistry, esp. without the resource bottleneck of lithium supply. Sodium ion wins on all those counts even though it's still, relatively speaking, a nascent technology.
Pretty much every pack spits cell data out over can, and contains hv contactors.
Projects like https://github.com/dalathegreat/Battery-Emulator
Standardize different pack coms for HV solar inverters.
The big hurdle here is insurance. It’s a regulatory nightmare, nobody wants to spend the money to provide the data that these packs are safe for grid tie. Even though they have the data for vehicle safety…
Even for the same car it's not trivial to use these all in the same system. It might even make most sense to couple them on the AC side but that would mean a lot of small expensive inverters.
that’s a odd way to do it, generally you just add more cells in each parallel group
Regardless most hv solar inverters are 600v or 800v so all those packs would work fine
The point that you're missing is that you can extend a packs life with a secondary application. That secondary application can make the cost of its first use lower making EVs more easier to adopt.
This requires more and more material. However we can recycle this material back through tearing it apart, which is a costly process.
It would be better to recycle a pack to its base material later than sooner. So the second life use allows for delaying the teardown & reclaiming process.