Just replaced batterys in mine today! I am bad on doing it usually wait till they start beeping. Hard wired with battery backup gives you a sense of false security. Gary
My house units are fine, but lately I've become more concerned about having so much wood stacked behind the detached garages. I also keep at least 20 gals of gas on hand over the winter and store it in the furthest garage. I looked into remote detectors and found these. Kidde Battery Operated Wireless-Inter-Connectable Smoke Alarm-RF-SM-DC - The Home Depot I'm thinking about putting one in each garage and another in the wood shed and put lithium batteries in them. My main concern though, is the one that will be by the wood. I'm wondering if being exposed to outside elements will set it off.
Those are about like mine. Check the pricing on a contractors pack (4 in a box) they were a lot cheaper. I picked mine up at Menards. Gary
Oops I just re-read the link you had. Mine are hardwired interconnected with battery backup NOT wireless. They may still have a contractors pack in that style though. Gary