I have 21DK with a WFCO 8955 converter (if that matters). I have 2 12v batteries, both in Attwood F27 Power Boxes
. That might seem like overkill for my trailer but I have other uses for them when not camping.
I just found that the power boxes have 30A fuses between the battery post and the external post. Does that match the capacity of the circuit breaker at the front of the trailer? While I do want fuse protection on the box itself for my other purposes, I don't want to undersize it relative to the demand of the trailer.
If the circuit breaker is 30A, I won't change anything but will carry spare fuses for the battery box. If the circuit breaker is > 30A, I may need to short across the battery box fuse holder when used with the trailer, and remove that when not camping. That way I'd rely on the trailer's circuit breaker.