Low voltage cutoff

I’m building a couple of 12 and 24 v boxes. For camping etc wondering how to build in a low / high voltage cutoff with DIYbms

Circuit breaker with a shunt trip seems to be the way to go attached to the relay, something like this: https://www.ebay.com/itm/ABB-SACE-S3-S3B-3-Pole-225A-240VAC-Circuit-Breaker-Shunt-Trip-Aux-Switch-TESTED/132336226104

They do come up cheaper and if you don’t need the really high amps, I got 2 for $240 if you’re patient.

I’ve heard Stuart mentioning contactors in the past to achieve high current cut-out more cheaply.
Some commercial BMS are using them.

this is some cheaper 12 volt boxes im playing with have shunt trip on my batrium

It is only AC rated

If you are referring to the breaker linked to they are also DC rated: