Lead acid batt. in home alarm system

Well, there's a good logical reason not to do this...

What happens when the power to the house is cut - For *ANY* reason, whether sinister, honest, deliberate, accidental, or otherwise? The "Why?" of the power loss is completely irrelevant. The only thing that counts is the "It's gone" part.

How well do you think the alarm system is going to work in that situation once you've converted it to run off the power line, instead of the battery?

Now think about how well the alarm works when the power goes out, but the alarm is powered by a battery that's kept on constant standby charge as long as there's power on the mains.

World of difference, huh? :)

In a nutshell, if you don't care that the alarm ceases to function if the power goes out for some reason, then sure - You can do exactly what you're talking about, with no problem whatsoever. If it's important to you that the alarm continue to function even if the power is cut, (For instance, if it has a fire alarm subsystem) then the ONLY way you're going to get that to happen is replacing the battery as specified.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
I respond to Email as quick as humanly possible. If you Email me and get no 

It's there so your alarm will still be up during power failures... either "real" or bad guy created.

And depending on the alarm and monitoring type, the absense of the battery may report a fault.

And if you get a reduced rate on your insurance for having an alarm, you might find that you've either cheated on your policy so that it's no longer in force if and when you need it, or that your premium goes up.

I'd suggest sticking with the battery - they're worth far less than the contents of your home.

Take care.

Ken

On Thu, 24 Jun 2004 13:08:20 -0500, Tam Nguyen hath writ:

I'm pretty certain that your home alarm system does *not* run off the battery. But, rather, the home alarm system keeps the battery "float charged" so that when the bad guys cut the power to your house and attempt to break in, the battery is Full Well Ready And Able to ring The Big Bell, dial the police, and trigger The Barking Dog speaker.

Jonesy

--
  | Marvin L Jones       | jonz         |  W3DHJ   |  linux
  |  Gunnison, Colorado  |  @           |  Jonesy  |    OS/2   __

higher

it

They should last several years and are not expensive, like mentioned they are a backup in event of power failure, also another bad point for you to consider, as most sounder boxes also have a battery backup they would in the event of a power cut or even pulling the fuse on the alarm circut be triggered, how could they tell it was you pulling the fuse or a theif cutting the wires?

See the replied/question below:

battery

the

higher

replace it

TAM: is the battery also powered the horn (thought it only power the electronic circuit)? I do believe that, in normal circumstances, the horn is powered by the wall powered transformer. If the power line goes out, would the batt is used to sound the horn?

TAM: same as the question above!

2004.

no

subject.

if there is a power cut the battery usually powers the entire system, PIR's / sounders/ contacts/ for how long depends on the size of the battery. The designers of these things really think it out, so like said before the box usually has a battery as a third line of defence and even may be triggered for a few minutes even by a regular engineer taking the cover off

I am not sure if the batt. also powers the horn when the line goes out, because there is a transformer in the wall socket that I think it is there to run the horn. So in the power line goes out scenario (regardless of circumstances), would the horn draws juice from the batt to blast?

Tam N.

battery

the

higher

replace it

Sound like the best way is to stick with the original design. I'll get the bettery replacement.

Thanks all for your opinions and helps.

Tam N.

battery

the

higher

replace it

There are so many types of alarms that it's impossible to do more than guess...

If you're adamant that you want to do away with the battery; then what you might consider is talking to your neighbors, and experimenting with it - at a reasonable time. Not too early; not too late; not the middle of the afternoon when the little ones are trying to have their naps...

I still urge you to use the battery, though. The designers put it there for good reasons.

Take care.

Ken

Almost certainly yes. At least in every alarm system I've ever had any dealings with.

Key words: "Under normal circumstances". The battery is there for the times when there isn't any power to the building. As long as there's power to the house, the entire alarm system is running from the transformer. If there's no power to the house, the whole system switches over to the battery in order to operate.

That would be the way to run the thing. Otherwise, your nice, fancy, expensive alarm system could be "shut off" by the bad guys simply cutting your power at the pole.

Same answer.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
I respond to Email as quick as humanly possible. If you Email me and get no 

Yes the horn does run off the juice provided by the incoming hot power but must have the backup battery for when the intruder cuts your mains. Also every unit I've ever installed won't give you a green on self check during start up if it doesn't detect a good battery.(The startup/selfcheck mode checks the battery for dwell and functionality and won't give green if there's no battery or if the battery is dead.)

The simple solution is to get a bigger capacity battery and perhaps one with longer life. I've used motorcycle batteries for some of my customers. They're vented wet cells that have much longer life than the closed drycell lead acids. there are also other types of batteries. gel cells, others with different chemical makeups that offer longer life.

Anyone have any specs on how long these "rechargeable batter nonspillable" should last in alarm (or similar) systems?

I have one for my electric gate & I notice that even though the whole system is only 1 year old, it didn't work when we had a power failure last year.

Also, anyone know the correct voltage that these batteries should be floated at? I used a multimeter on mine, and it is sitting at 14.3V DC. Will this harm the battery?

Dave

The email address used for sending these postings is not valid. All replies to the group please.

You didn't mention the Ah rating of your batt.(since it's for a gate I'm guessing that it's at least 9Ahs.)

14.3 is just a static reading and about right. Test it under load and take a current reading. You'll find that on a good battery it'll drop to 11.9 to 12.4/5 on average on a load. I've seen some replace sealed lead acids with sturdier types of batteries. depending on how strong the charging circuit is and it's output rating you can go up to a car battery. I've used large motorcycle batteries as replacements for SLA's for things like garage door openers and warehouse door openers. Usually 14 to 20 AH in size. Good thing is you can tag on a small 1amp trickle charger if the control units charger isn't up to it. Also you can remove it at intervals to give it a 4-8 amp quick charge to burn off any sulfation, thereby prolonging battery life. Since it's a wet cell you can check specific gravity as well, letting you know when it's time to change the acid or swap the battery. Having a transparent case you can also inspect for plate erosion. I get as much as 8 years off wet cells vs. the 2-3 for SLA.

It's only a 7 amp-hour

I have to replace it anyway by the looks of it so I'll see if I can get something bigger, and do some tests once I install it.

Thanks,

Dave

The email address used for sending these postings is not valid. All replies to the group please.

Most horns and annunciators draw more current than the transformer is designed to provide, and rely on the battery.