[DanielHB]

Balancing multiple battery packs at different wear levels is a huge nightmare. You have to run rebalancing operations all the time and on used packs it can be quite dangerous to trigger a thermal runaway.

If they do it with different types of batteries it is even more complicated, like you need to write some custom software to sync all that up. This is not a trivial project.

[rini17]

They reuse inverters too. So the packs are separated, no need to balance.

[rojcyk]

So? They considered it to be worth while for them. Thus are working on it.

[DanielHB]

I know, it seems it is fairly large operation however, if it wasn't I would assume it was a PR stunt.

This is definitely not worth doing for small scale operations. As far as I know there is no generic solution for doing this kind of thing (I used to work in the area, but not directly on the BMS systems).