Just have to piggyback on this conversation;
Took my trailer in for roof mtce. and to clean/service the AC. Called me to pick it up. Got there and knew something was wrong just by looking at the trailer. Tried to raise the tongue jack and it was dead (new Interstates when I took it in). Plugged the truck in and I heard all the brake magnets kick in. They had pulled the breakaway switch at some point and just left it out until the batteries were dead (fully charged when it went in). I was not happy.
I advised them that completely depleting the batteries would reduce the cycle life by about 50%. They disagreed and said depleting them had minimal effect...maybe 5%. I sent them the link below with the Interstate guidelines for their deep cycle batteries. Note that they should not be depleted below 50% and then note the chart on what discharging them does. A complete discharge reduces the remaining battery cycles by over 88%. So, as one poster mentioned, you get the trailer back and charge the batteries and go on down the road. Then you wonder why in 6 mos. the battery won't hold a charge.....now you know. It was news to the dealership folks and I'm sure it happens everyday. As I told them it was their mistake and I don't intend to pay for it in a few months.....it is awaiting new batteries in the shop on their dime as I write this...as it should be.
https://www.intechtrailers.com/image...nce-Manual.pdf