What is the effect of the rated current for a breaker when a 230V 6A rated circuit breaker is used in a 24 V DC circuit?
A household circuit breaker (of relatively low amp rating) can be tripped by the levels of current that the batteries are capable of. However, will that protect what you think it will protect?  That is, if a short occurs, will the wiring between the short and the breaker be sufficient to carry the current required to trip the breaker? Or will the wires simply burn?  This arises because with a load rated at only 180mA, the wiring to and within the load circuitry is likely to be quite fine.