I thought about this and opted out as well. The amount of energy in a battery on a boat 50 miles off the coast scares the heck out of me, so I feel like I am paying for confidence in my storage. Building a battery is the easy part, but how do you gain confidence in your cells and internal components, weld quality, etc? If they are saving you a bunch of money are they really what someone is saying they are? Will Prowse does a bunch of buy and tests, and he is definitely a good source to start into this type of thing, but he is doing it in a garage and not on a boat. I have built a lithium ion battery out of 60 18650 cells (almost a thousand amp hours) that's in a home built skateboard, and I broke a weld on it and almost turned it into a fireball doing 25 miles an hour in traffic. There is just so much that can go wrong with that amount of energy, it just doesn't seem like a great place to save money in my opinion. But, if you do it, definitely post your journey, I would love to see it!