Yeah, I should have updated the thread. I adapted one of Will's milk crate builds, leaving out the solar charge controller, and using 4x 100Ah packs from batteryhookup.com. Way overkill for the power capacity, but it's working well so far.
This kit includes a 4s 100a Lifepo4 BMS with programmed low temp cutoff at 0 degrees Celsius (32 Fahrenheit) to protect against charging in freezing temperatures. Every part of this kit can be bolted together 5/16" regular nuts and bolts you can find at home depot. We recommend using a lock...
Overkill to be sure, but it included the BMS, and I didn't need to mess with bus bars as the cell packs have flexible wires. The four cell packs fit very nicely into the milk crate. Otherwise, the build largely followed Will's video here:
...with the obvious exception of the solar charge controller. I used a 20A power supply instead of the 10A one he linked from his video, and a smaller fuse box. Also added a circuit breaker (in the red 3D-printed bracket at the bottom of the image above) to disconnect AC input power.