Kidde 21025831 Power Source Replacement Batteries

I could not find these in any of the stores near me.

I was sick of regular batteries going bad. Glad to find these that are made for smoke dete

I have a  Kidde KN-COSM-XTR-BA Nighthawk Battery Operated Combination Smoke/Carbon Monoxide Alarm with Voice Warning, Intelligent Alarm Technology .When its low battery alert started up, I looked all over for replacement batteries. Seeing that these batteries with Prime shipping would arrive over a week before Home Depot's delivery (being unavailable in my local Home Depot store)... and seeing as how Home Depot also charged $2.50 more for the same product... I decided to order from Amazon.These are AA batteries that come in a 4 pack. The package was brand new. After placing the batteries into the alarm, the alarm went through its test procedure and now seems to work fine. Since the alarm only needed 3 batteries, I'm holding onto the extra.I am docking 1 star because the old batteries, which came with my Kidde alarm, lasted from late October 2013 until late June 2015 when the low battery alerts began - around 4 months less than the 2 years guaranteed by the manufacturer. Still a relatively minor complaint.Bottom line - get these to extend the life of a reliable ~$40 fire and carbon monoxide detector to keep your family and/ or business safe.

Package says best if used by date on bottom of battery. ( month/ year). There is no expiration date on batteries or package

These batteries function like I expected. The smoke.alarm I have required using these particular batteries.

Smoke alarms

I've tried countless batteries in my A/C Kidde smoke/co2 detectors after the included "Power Source" ones died. Literally 18 hours later it would constantly complain about low batteries. Energizer, Rechargeables, Duracell, etc. All had issues. You NEED to buy these special AA batteries. Eventually I just gave up and replaced them all with 10 year "worry free" Kiddes because buying these special batteries is expensive, annoying, wasteful, and pointless.

To replace batteries in smoke detector