My batteries are 16 x 280ah cells. 2 hours after they show up in my driveway, they are part of my system.
Building them myself saves me $1k per battery.
Ok, but the parts don't order themselves. You knew every product you needed to buy and where to buy it, and that process took you zero time?
I've spent 40+ hours just figuring out which cells, busbars, BMS, Anderson connectors, switches, fuses, breakers, cable, torque wrench, wiring, battery charger, fuse, fuse block, circuit breaker, battery shutoff switch, ring terminals, crimpers, wire strippers, electrical contact grease, heat shrink tubing .... etc. to buy. A couple of the components I had to buy twice because I screwed up the first time, like I bought the Daly BMS before I figured out that JK-BMS was a better choice. Same with the busbars. Literally every component from large to small I needed to research and find from scratch.
Also I needed a wiring diagram, that took a good 8+ hours to come up with.
Needed to flash the BIOS on the BMS.
Needed to learn the BMS software and settings.
Every step took longer than I expected.
Also in my case I need to add the time I spent worrying. Probably a good 60 hours spent worrying. And time spent procrastinating. At least 200 hours of procrastination time. Time spent building the boxes. Probably 30 hours for that.
I was intimidated at first. Even as a 40 year electrician. (To many scary stories on the internet)
But I couldn't pass up on the savings, so I researched it and gained confidence.
And how many hours did you spend to "research and gain confidence" ?
I'm trying to take my research time into account. That all has to be amortized into the cost if you want to accurately calculate the true cost of DIY vs. buying off-the-shelf.