1 Noco genius Smart car battery charger. New I never needed it in the end (price new 29.90$)
https://www.amazon.com/gp/product/B07W46BX31/ref=ppx_yo_dt_b_asin_title_o04_s01?ie=UTF8&psc=1

1 battery disconnect switch - to open the circuit when you leave your car idle for long so the battery doesn't discharge (price new 9.90$)

1 automotive power relay G8HL-H71
https://www.amazon.com/gp/product/B09XDJQ6B8/ref=ppx_yo_dt_b_asin_title_o04_s02?ie=UTF8&psc=1