I have the referred product. I noticed the green light was off. So changed the battery -9V Energizer. After 8 days it started warning that the battery is low. I have also noticed that it does not function without battery. Probably it is not wired???Could you please advise if I use a different battery, it wil last longer??? Has this product to wired as in the case of the smoke alarms which I have in the 1st floor and basement?