For the HomeGrid Stack'd it's more than cells, BMS and a case.
- Each 4.8 kWh "slab" has a BMS that manages the cells (just like everybody else)
- Each stack has an overall BMS in the head unit that manages the 3-8 slab stack
-- That overall BMS communicates externally to inverters (charge/discharge limits and the like) and distributes power to/from the slabs
-- Internal to the stack it actively balances the slabs to keep them in lock step (the slab SOC's
don't wander) and it monitors SOH for each slab
That overall BMS can also serve as the "master" for multiple stacks and communicate with the inverter system on behalf of the entire battery array. If you had a maxed out array of 15 stacks the master BMS/stack could request as much as 4500A Charge/Discharge (200+ kW) via closed loop.
Additionally, there's centralized fault isolation (w/ look-up codes - voltage/current/temp/comms/internal failure) for each stack and cloud and local (app and software based) monitoring (via WiFi) for the battery array (albeit the phone app was
waaaay beta when I tried it). I can't comment on the cloud-based monitoring as mine are kept offline.
I'm not trying to convince anyone on here as there are WAY more cost-conscious options with 90% of the functionality for well-read hobbyist like those of us on this board...BUT, it
is a product with unique features and to say it's equivalent to a server rack setup is incorrect. HomeGrid makes the most sense if you were going to build a setup for your rich grandma one state over who knows nothing about batteries/power nor would ever care to. Totally set and forget for the life of the system; bulletproof and safe while not looking like a bowl of spaghetti in grandma's 4-car garage.