[serialk11r]

If you search you'll find a lot of posts.

Antigravity marks things up about 2.5x in exchange for good customer support. High current BMS with bluetooth costs about 100 bucks and the cells cost on the order of $2/Ah these days (30Ah x 4 in series = about $240). You can get them even cheaper on Aliexpress but the cells may have reduced capacity from being used or QC rejects.

There's zero reason to assemble the pack yourself nowadays, as they make plastic casings that fit standard car/motorcycle battery sizes with standard size terminals.

Another thing to beware of is electronics may not play nice with the BMS' charging cutoff. I have small ultracapacitors in parallel on my car to provide momentary backup power to avoid pissing off the car.

If you don't have freezing temperatures go LFP, otherwise you need LTO. Even though they work at much lower charge than lead acid, I would still have 20Ah at a bare minimum on a car so you don't have a dead battery if you go on vacation.