Just toured a facility using a massive industrial battery system - what should I know about these setups?

I was recently able to visit a manufacturing plant that installed a huge industrial-scale battery energy storage system (BESS) to manage their power needs and for backup. Seeing the physical scale of the containers and learning about the peak shaving and emergency power capabilities was pretty eye-opening.

My company is starting to look into this to reduce demand charges and increase our energy resilience. For those of you who have worked with or specified these systems, what are the biggest lessons learned? What questions should we be asking vendors upfront? Any major pitfalls to avoid during planning and installation? I'm trying to build a knowledge base before we get too far into the process.

I found a resource like this one on industrial battery suppliers helpful for basics, but I'm really looking for real-world project experience.