Thank you to all for your responses. There is some really good advice about leaving the breaker off before plugging in. The thing is the RV was plugged into the outlet at home for a week and there was no problem. I took my sister and brother-in-law into the rv to show it to them and turned some lights on and off - nothing major. Then we left and 4 hours later I took another friend in to show it (nothing was touched, nothing left on, the plug stayed plugged in) and when I turned on a light it was dim. I guess the breaker had blown at that point, OR the breaker had blown the week before, but because we weren't in the RV at all, when I turned the lights on the first time, it drained the batteries and by the second visit they were nearly dead. The breaker could have blown when we plugged it in the week before, and it took a week for the batteries to drain - is that possible?