Inexpensive low profile smoke alarms (4.0)

Standard basic smoke alarms. Easy to install and low profile design. Best part (besides price) is how small they are. The only thing they're missing is an indicator light.

SS-770 Acceptable very Economical Smoke Alarm, long battery life (4.0)

SS-770 Acceptable very Economical Smoke Alarm, long battery life

The Universal SS-770 Ionization Smoke and Fire Alarm is ordinary but unusually small: 4-inch diameter, 1-inch thick, white plastic. Extremely economical $4.45 from HmDpt 6/16/10. Manufacturer generic six page insert: [...]

This smoke alarm works but is as basic as possible: 9V battery only, ionization detector only, no LED at all, no hush button. Just a weekly test button and the alarm beeper. It comes with a basic non-alkaline 9V carbon-zinc battery that should last for about 4 years. A higher-quality battery would last longer. The alarm itself is supposed to be replaced ten years after the date of manufacture. It comes with a worthless 5 year warranty which requires a payment of $4. Made in China.

The missing hush button is the worst feature of this alarm. You are supposed to mount it on the ceiling, or within 12 inches of the ceiling. But if it goes off because you burned the toast, it could be hard to reach! Even after you have figured out how to rip it off the wall (twist and pull), the irritating alarm cannot be silenced until you figure out how to disconnect the battery, which is not easy to do if you are in a bad mood.

The smoke alarm mounts on a round white plastic base plate, which is screwed to the wall or ceiling with two long skinny screws that are only partly threaded. The screws work OK on walls but would not securely mount in to ceiling sheet-rock. Secure mounting would require larger screws and/or plastic sheet-rock inserts.

A battery-operated smoke alarm like this is a great life-saving tool for people who sincerely want to have this kind of protection. But if you are a landlord dealing with tenants who may not properly replace batteries as needed, or someone who just never wants to be bothered with taking care of equipment, you need alarms that are wired into the AC power.

Because this is an ionization (radioactive) type of smoke alarm, it uses very little battery power. There is no need to replace the battery twice a year; that would be wasteful. The 9V battery should typically last much longer than one year. If you are comfortable using a volt meter, measure the battery twice a year and replace it when it gets much below 9.0V. The SS-770 should go on working until the battery gets down to about 7.5V, at which point it will start chirping about every 40 seconds.

Based on current measurements, an ordinary "heavy duty" 9V battery should last about 4 years, a good alkaline battery should last about 6 years, and a super-duper Lithium battery should last over 10 years.

These are actual power measurements:
9.5V 6microAmps + current spikes

Low-power measurements:
3.2-3.6V (3.2-3.8V) quiet fast chirp
3.6-5.2V (3.8-6.2V) 3 beeps, pause; repeat
5.2-7.3V (6.2-7.7V) quick chirp every 41 seconds - time to replace the battery!
^volt range going down^ (^volt range going up^)
non-techical translation: don't let the battery voltage get below 8 volts