Clean electricity generation paired with the first grid-level sodium battery energy storage system can bring costs down to just $0.028 per kWh. The 10 MWh storage capacity is executed with sodium-ion cells that can be charged in just 12 minutes.
Time until full charge isnt really a relevant metric for utility storage, you want larger storage, which would increase full charge time. Rate of charge is what matters.
The C rating is generally what battery charging (and discharging) is measured in. C being the capacity of the pack. So if the pack is 10 Ah and it takes 10 hours to charge it's 1c, if it takes 1 hour to charge then it's 10c.