Our external alarm box is still electrically OK but looks very scruffy so I'm going to replace it. Googling, I see that many current products have a built-in battery, typically NiCad rechargeable. But in my experience these batteries are not maintenance-free. Installing the unit using my fully extended ladder will be hazardous enough, but I don't relish having to get up there again regularly to change the battery.
Anyone with any practical experience of these have any advice please?
The bell box batteries seem to last forever (or as near as dammit) in my experience (as I found out when I opened our bell box on our very old system after it had been powered down for over a year).
I wouldn't worry about it.
Tim
Most rechargeable batteries tend to have a life measured in charge/discharge cycles. Since a bell box one will be very rarely used they tend to have a very long life. 10 years isn't unusual.
Thanks both, appreciate the fast replies.
BTW, I note that these NiMH or NiCd batteries typically appear to be
7.2V or 8V, not 12V like the specified power supply. Anyone know why please?In message , "Dave Plowman (News)" writes
The lead acid one in our control panel seems to get changed every two or three years.
Last time I queried it, the service engineer said the location was probably too warm.
regards
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Lower cost mainly but also the need to drop a volt or two to charge the batteries constant current.
In my limited experience, current practice is to boost the battery voltage on alarm using additional circuitry. I have an Elmdene internal sounder here with only a 4 cell (4.8V) battery which is just as deafening on battery as it is on 12V.
It would be worth checking that your chosen sounder is as loud on battery as power.
The service engineer?? for a friend did that. He recycled the batteries (you could tell from the date code they weren't new) every 2 years and charged (exhorbitant) new price for them. The last one he changed is now about 7 years old and was still fine on a recent test by me.
Do you get to keep the old one? They'd have to be *very* badly treated to only last two years.
I'd change the service contract.
The bell box is really a stand alone device - so its own electronics and sounder can be powered by pretty well any voltage the maker wants. The 12 volts sent up to it to charge the battery etc from the main panel will be regulated internally to what's required. I'd guess they'd use as low a voltage as is practical - as pro rata battery price increases with more cells.
How long did it power the alarm for in "standby". How long would it run in "alarm" mode driving the sounder(s)/strobe(s)?
I get about 3 years from the ones in my UPS. They are too warm IMHO at around 40C. They last a little better since I disabled the weekly "self test". I don't think the float voltage is overly high (2 x 12v series connected have 27.7v across them) but this is an APC UPS...
In message , snipped-for-privacy@privacy.net writes
There is no charge beyond the annual service fee.
It is certainly getting pricey:-(
If I extend the system I will undertake my own servicing.
regards
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I have one removed from an alarm after 4 years, which was what that company used to do. The label says installed 11/94, replace by 11/98. It's not been in an alarm since then but it still works fine, and it's capacity is still slightly higher than the 7Ah on the label.
The thing that really kills them is running them flat (and it may be even worse if you leave them flat). A good alarm will have a circuit to protect the battery from being run completely flat.
They are treated *very* badly. It seems to be a ploy by the UPS manufacturers to ensure on-going sales, although the excuse is they have to charge them fast so they're quickly ready for another discharge.
My alarm does a twice daily battery check IIRC, although it doesn't try running the batteries flat.
You usually find you don't own a system which is on a maintenance contract -- you just have a lease on it and you end up having to pay for it (again) if you want to take it over.
And the maintenance contract may well be a condition of your insurance.
In message , Andrew Gabriel writes
Interesting.
So if I stop paying the maintenance charge on a 13 year old system, they are going to come and remove it?
Actually, by extending, I mean a stand alone, purchased alarm, self installed. That way I will have engineers codes and a full knowledge of how the system works.
regards
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Installed after a burglary, there was a *flavour* of requirement from my insurers, but they confirmed in writing recently that it is not mandatory.
The extension will be to cover farm outbuildings for which there is no capacity or practical method of being added to the existing. My proposed cable routing does not comply with the rules specified by my current service anyway.
regards
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Not trusting insurance companies I'd look very hard for weasel words in that letter. Something that although a maintenance contract is not a requirement for cover, cover is reduced or not available for certain things without one. This might just be a "*" footnote in the letter that refers you to clause(s) in the policy document. ie the weasel words are actually in another document.
I don't think an occasional fast charge is a problem provided you drop back to float at the appropiate charge level. It's not that difficult to do for SLA's. 27.7v across two nominally 12v SLAs is 13.85v each, a light float voltage would be 13.5v fast charge 14.4v. I think they get cooked by the heat.
They may well remove the panel, sensors and bell box, but I doubt that they will remove the cables.
Adam
Just chop them off short to make re-use difficult...
I'd tell them to remove all their stuff or none. And make good any damage afterwards. They'd only be removing the old stuff out of spite - it's very unlikely to have a value exceeding the labour costs of removal.
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