One can also look for used car batteries like these VW/ID 8s 6.85kWh and with a decent BMS. Some times one can find some cheap ones.
I use them in my project @How sustainabile an ESS can be? and after 2Years i can see no degradation at all. These high quality packs much more safe as an DIY pack off 18650. The two internal temperature elements fit to JK BMS or Dali (others i have not checked).