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How to Re-route 9 Volt Batterie from Smoke Detector Answered

Hello, We have 14 feet high ceilings and smoke detectors in 4 rooms at that height. Not wanting to crawl up the ladder to switch the 9 Volt batteries, one would think you could simplify this task. Use a 9 volt battery connector to connect to the battery ports in the smoke detectors, a wire each to a central point in the house, such as a hall closet, where each wire ends in a 9 volt battery box. I can find various 9 volt battery connectors to purchase, have umpteen yards of low voltage wire (from sprinkler system installation). What I don't know is, is there a limitation on the length of wire I can have a 9 volt battery on one end, and the smoke detector on the other end? Thank you. Stefan

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steveastrouk
steveastrouk

7 years ago

Its quite normal to have externally powered smoke detectors, but there are very strict rules about the wire that can be used to wire them together.

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mpilchfamily
mpilchfamily

Reply 7 years ago

But don't those detectors still have an internal battery in case there is a power failure? I know the smoke detectors in my apartment are wired into the building with nice thick solid copper wire. But they still take a 9V battery in case the power goes out.

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steveastrouk
steveastrouk

Reply 7 years ago

There are two methods, one relies on charging internal batteries, one relies on a single operating battery at the "control panel"

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mpilchfamily
mpilchfamily

7 years ago

Interesting idea. But what happens when that small room is the area that catches fire? Imagine. It's 2AM, fire breaks out in the closet. Possibly due to a failure of one of the 9V batteries your using. Now the fire renders all the detectors useless before they can sound the alarm. Now you and your family don't realize the house is a blaze till it's too late.

Here is what you should do. Go out and buy the new smoke detectors that have a 10 year battery life. They come with a battery built in and do not require battery replacement. It is recommended that smoke detectors be replaced every 10 years anyway. So take the time and energy and just replace what you got with ones you know will last 10 years.

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Kiteman
Kiteman

Reply 7 years ago

+1

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verence
verence

7 years ago

The voltage drop along the cable depends on the resistance of the cable in Ohm/m (or Ohm/feet) and the current (in A), the detector draws. The drop is then the product of length of the cable * Ohm/length unit * current.

You can't change the current consumption of the detector, but you can control the resistance of the cable - don't use the thinnest cable (like magnet wire) but something like AWG25 or thicker and keep it as short as possible.

Apart from the voltage drop, you have to take the antenna effect of a long cable into account. A long cable may pick up some ambient electro magnetic fields and supply the detector with 'noisy' power instead of clean ripple free battery power. I have no idea, if your detector will be affected. Just try it.