Another Battery question from New Owner

[roned2]

We picked up our new 3124KS a month ago from Ohio. We brought it home and plugged it into our house power. Took it to our storage area and left it for about 3-4 weeks. We went to hook up after this time and the jack would not work as there was no power. Hooked it up to the tow vehicle and away we went.
My question is how long will the battery last when sitting in storage? I don't know yet if this is a charging problem or not. We were plugged in at the campground recently so we will see what happens next month.