I believe there is a government regulation that requires a breaker on the negative cable from the battery to the distribution panel. My last SOB trailer had one hidden under the bed. Almost impossible to find. IF I remember correctly, the breaker is supposed to be within 3 feet of the battery. Follow the negative cable from battery to distribution panel. If there is anything on the cable, it is likely a breaker and it is likely to have tripped. Good Luck.