I'm assuming these are Kidde 1276 smoke alarms. When you replaced the batteries, did you actually disconnect them from the wiring? Here's what you do. Remove the detector from the base. You'll notice a small plug at the back of the detector. You have to squeeze the two tabs on either side together while gently pulling on the plug. Remove the batteries. Leave the unit unpowered for five minutes. While you're waiting is a good time to take out your vacuum cleaner and with the soft brush attachment, vacuum all around the detector side vents and back. When the five minutes are over, replace the batteries. Make sure they're aligned correctly and you've pushed the little red tab down properly. Now press and hold the test button until the unit beeps. This will make sure the unit functions on battery power. If the unit doesn't respond, open the battery compartment and make sure the battery is making good contact with the terminals. If the unit responds properly, plug it back in and relocate it on its base. Push and hold the test button again. Make sure ALL of the interconnected smoke alarms are responding as well. Move on to the next detector and repeat the process.