Weird things coming home from vacation

Jaimie and I prefer to vacation in Hawaii, it’s beautiful, it’s easy, and it’s not too much work. However, the last two times we’ve gone, the only two since we’ve been in the new house, we’ve come home to some strange things. The first time we came home from a week trip and all of the smoke detectors we’re going off. Apparently they had been for the entire afternoon. There’s nothing in the world that will get your adrenaline pumping like coming home to your newly purchased home and hearing all of the smoke alarms going off. Nothing was amiss in the house except that we had let the heat go down, but not <50*. We figured that this must have somehow affected the smoke detectors.
What was really strange was that none of the smoke detectors are attached. They’re all simple battery units, but three of them were going off in three different rooms of the house. They also weren’t CO detectors or anything else fancy.
After going in and pulling the batteries to get them to shut up everything was normal. Then after putting the batteries back we found that they were all dead, they kept doing the low battery chirp. So, one trip to Home Depot later, I pick up new batteries and new smoke detectors just to be sure, had wanted to get CO detectors anyway. Haven’t had any problems since then.
This time on returning from our latest trip to Hawaii, we’ve got another smoke detector dead and chirping. We didn’t allow the house to get abnormally cold this time as we kept the heat program running through the week. Just a strange coincidence to come home to.