Good time to replace 9 volt smoke alarm batteries?

softdownsoftdown Solar Expert Posts: 3,494 ✭✭✭✭
They measure about 9.6 volts when new. Guessing that ~9 volts would mean they are at ~ 50%. 

Every fall, when the temperature drops, I am awakened by the chirping of weakened smoke alarm batteries. Both the city and the rural dwellings - the battery numbers add up. The cold temperatures significantly weaken the battery outputs. This change is most dramatic after midnight as I tend to sleep in cold conditions - think 50s, sometimes 40s.

Happened at 12:30am. Feeling sleepy and knowing how many smoke alarms there are I just stuffed ear plugs in. It was still hard to find the offensive battery in the morning. I often place a smoke alarm every 5-10'. I use a bunch of them. 

Narrowed the suspects down to three smoke alarms and a carbon monoxide alarm. Found suspect voltages ranging from 7.7 to 8.8 to 9.0. In the past I have simply replaced all 9 volt batteries. That may be wasteful and lazy and bad conservation. 

What makes it so hard to find the offensive smoke alarm? Sometimes 2-3 are doing periodic chirping. Really throws you off. I wish they chirped much more frequently. 

Anybody have pertinent knowledge on the subject of 9 volt battery longevity vs. voltage output? 
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries

Comments

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    I think they're 6 x 1.5v nominal cells.  An alkaline would be dead at ~1.1v/cell, so ~6.6v for a 9v nominal?  50% no-load voltage ~1.3v x 6 =7.8v.
    https://en.m.wikipedia.org/wiki/Alkaline_battery
     
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    In Canada, we're encouraged/nagged to change alarm batteries proactively when the DST time changes in spring and fall.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭
    Or change to the 10 year lithium ones , i think more cost effective in the long run .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    Presumably 10 year lithium is for hardwired smoke detectors (with the battery just for backup)?  Standalone are quite common here.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • softdownsoftdown Solar Expert Posts: 3,494 ✭✭✭✭
    Bought some rechargeable 9 volt lithiums but reluctant to place in a device that I might somehow lose. Rechargeables sometimes hold a lot of energy but suffer from a short life during months of stand by duty. They are good for high drain devices that are frequently swapped out. They were perfect for the high drain flash usage of event photography for example. With most images taken in dark indoor settings.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • mike95490mike95490 Solar Expert Posts: 9,091 ✭✭✭✭✭
    I would use 10 year rated Li 9V batteries (non-rechargable)   They have long life, and if they did fail, you still get the chirp.

    I'm so disappointed with smoke alarms. In 8 years, in  a house with hard wired, interconnected AC /battery backup alarms, we had 3 or 4 go bad in the first 6 months, then about 1 every year since then.  $40 - $50 each.

      I only replace batteries when they start to chirp.  Cupping your hands around your ears, helps focus the area the sound can come from. I can narrow it down after 3 chirps, to the alarm.   ( local FD pushes the mantra "change batteries when you change your clocks", which I think is BS,  10 batteries, 2x a year, when they are supposed to be good for at least 2 years with no alarm events, is wasteful. )
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
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  • softdownsoftdown Solar Expert Posts: 3,494 ✭✭✭✭
    What made it so hard is that I was looking for a smoke alarm. It was the carbon monoxide detector. Last year I had two or three chirping which was also difficult. 

    Since Duracells are prone to leakage I should think about using AA and AAA lithiums in most everything. Though they did bump up their price recently - perhaps addressing the known leakage issues. 

    Though some devices will not work due to excessive voltage with lithiums - which tend to measure over 1.75 volts. Not a risk unless several batteries are used I find. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭
    The 10 year life ones here have a sealed battery .... so another throw away item. No not hard wired. 
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • softdownsoftdown Solar Expert Posts: 3,494 ✭✭✭✭
    Estragon said:
    In Canada, we're encouraged/nagged to change alarm batteries proactively when the DST time changes in spring and fall.
    That is ridiculous. Pretty sure my batteries last at least 2-3 years. Though some will use the cheapest batteries in a smoke alarm - a questionable idea. 

    Had a tenant who always stole the 9 volt smoke alarm batteries so the government inspectors always flunked the smoke alarms - Section 9 government subsidized. The troubles I've seen. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • Marc KurthMarc Kurth Solar Expert Posts: 833 ✭✭✭✭
    The 10 year life ones here have a sealed battery .... so another throw away item. No not hard wired. 

    Yep, the battery is sealed inside the detector.  I am 2.5 years into the first one that I bought.
    It is important to have both photo-electric and ionization type detectors. Nowadays, you can have both in one unit, but they cost more.
    Just the opinion of a guy who lost his home to a fire.
    I always have more questions than answers. That's the nature of life.
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