Mitsubishi energy storage, page-3

Interesting Mega.
This description also puts all power storage systems into perspective WRT Pumped Hydro which is still 95% of the USA's grid energy storage.
Buzen
Also for Buzen "the storage devices contributed 30 – 40% of the cost of an energy storage system.  That becomes a recurring operating cost when the storage devices reach their cycle life limit and need to be replaced." (which is 4000 to 5000 cycles) so a large cost in ongoing replacement of batteries