The battery contacts of a sensor sometimes corrode due to age or issues with the battery. Such corrosion will inhibit the battery from properly powering the sensor and it will require battery replacement more often than the other sensors.
If your panel reports "low battery" or "loss of rf supervisory" regarding a sensor that has recently had the batteries replaced, corrosion could be the cause. Please check the contacts for corrosion which may appear as a discoloration or build up on the sensor's contacts. You can try to clean the sensor's battery contacts by using:
Cotton swabs and rubbing alcohol;
Clean, soap/detergent free plastic pot scrubbers; and/or
Very fine sandpaper.
Also, for barrel type batteries (like AA or AAA), make sure the batteries are fully seated by firmly pressing and rolling them with your thumb. This will make sure they are properly seated on the contacts as well as creating friction to remove corrosion. If you will have issues after this, we may need to do an onsite service call. Contact the Reed Security support desk for further assistance.