Alarm System Backup Battery Questions - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: January 07, 2014, 02:49:51 am
content: Hi Folks,I have some simple questions about replacing an alarm system backup battery and I just want to confirm things before I blow anything up (as Dave says "release the magic smoke").QUESTION 1:I posted a picture of the battery in the alarm system (SLA type) 12V 4 Ah with a close-up. I assume this is a standard lead-acid type as found in backup UPS and other devices. It has been in the system for about 5 years so I guess it is no longer charging well, as the alarm system is complaining.So I bought the larger 12V 9 Ah battery you see in the last photo... Will this work ok? I assume it will just last longer in case of a power failure. I want to know if it will make any difference to the Alarm System charging circuit... Will this larger battery cause issues with charging or overheating or current?QUESTION 2:I have a car battery charger that I use to top-up a car battery in the house as a backup and for inverter uses in an emergency. It outputs either 6V or 12V and let's me choose between various size batteries (small, medium, large).Can I use this car-battery charger to top-up the new 12V 9Ah battery I just bought? I want to make sure it is charged up before I put it in the Alarm System since I don't know how long it was sitting on the shelf in the store. Is there any reason or difference in charging these types of sealed UPS or Alarm System batteries with a charger for 12V car batteries?QUESTION 3:When I replace the battery, can I simply tag on the new battery in parallel to the old battery with some alligator clip wires while I disconnect the old battery, then slide the metal C clips onto the new battery clips? I just don't want the alarm system to think the battery was disconnected as it will set off a distress signal I think and bother the alarm monitoring station. So if I just connect red-red and black-black while I swap the batteries, it should just temporarily turn the situation into a 12V 13Ah battery (4Ah+9Ah)? No issues with the alarm system or charging circuit?By the way, I am assuming a lot of things here which may not be the case. Please help me out if this is not the case, I would greatly appreciate it. I assume the alarm system continuously monitors or trickle-charges that attached battery... I don't know whether it will detect anything funny going on or damage stuff if I swap in a different type of battery. Thanks!

author: bgsteiner
author_rank: Contributor
timestamp: January 07, 2014, 03:17:01 am
content: You are correct in assuming that it should work for the system. Iw will just last longer as it has a longer amp hour rating. As for the charging system with a lead acid that is constantly in the unit it will most likely just be a trickle charge unit to keep it topped off and the only change is that it will take longer to recharge off of the system although I recommend using a proper charging system if it does drain the battery after loosing mains power to increase the life of the battery.

author: Rerouter
author_rank: Super Contributor
timestamp: January 07, 2014, 03:19:30 am
content: 1. You should be able to swap it, as for the higher capacity, it could be an issue depending on how cheaply the charge controller is made, if it has a current limit your fine2. there is no difference, but a low charge rate is preferred to keep the cells cool,3. the better option is to measure your battery chargers open circuit voltage, if it doesn't go above 15V, leave that in parallel instead as a new fully charged battery in parallel with a flat one can shunt enough current to pop the flat one, (battery acid bomb)your not swapping the type of battery just the capacity, and while i have no idea on if its monitoring sudden increases in voltage (that would be an odd attack and i would think it would be protected against someone shunting 240V mains up there) it could be.

author: Unknown
author_rank: Unknown
timestamp: January 07, 2014, 05:35:37 am
content: Quote from: edy on January 07, 2014, 02:49:51 am5 years is about as long as you would want to leave a battery in your alarm before chaning it. From the manual for your alarm ;Standard Battery Charging Current: 400mA (280mA forIMQ). To be used with 4Ah or 7Ah batteries.High Battery Charging Current: 700mA. To be used with 14Ah or 24Ah batteries.So I would say that according to the instructions you shouldn't fit anything larger than a 7Ah.Quote from: edy on January 07, 2014, 02:49:51 amUnless the SLA is nearly flat then I wouldn't bother. The panel should just charge the new battery.Quote from: edy on January 07, 2014, 02:49:51 amYou should be able to just remove the battery and stick a new one in without anything happening.

author: SeanB
author_rank: Super Contributor
timestamp: January 07, 2014, 08:23:14 am
content: Unplug and plug in the new one. You have some CaddX system, and it will charge the battery with no problem. Will last longer if the power goes out, and will charge in about 2 days. Battery test might still tell you a fault for the first 2 hours or so, depending on the configuration of the battery test duration ( normally every 5-15 minutes) until it is charged above the low level voltage. If you want to check the new onr just measure the terminal voltage, if above 11V it is fine. If below connect to a charger for an hour to bring it up a little. The old battery probably has a voltage below 10V, as one cell is either shorted or nearly open.

author: nihilism
author_rank: Regular Contributor
timestamp: January 07, 2014, 10:09:15 am
content: New battery will work fine. Larger capacity just means it will last longer when the power is out and will just take longer to fully re-charge once it comes back on.Don't charge it with the external charger, more likely to do more harm than good if it is for regular vented lead acid batterys - the charge current may be to high for the sealed battery.The panel will charge the new battery once it is installed.I wouldn't worry about disconnecting it sending any alarms if it is already indicating a low battery, just unplug the old and plug in the new.I install commercial security systems for a living.

author: lewis
author_rank: Frequent Contributor
timestamp: January 07, 2014, 10:45:14 am
content: Do NOT use a car battery charger to charge sealed lead-acid batteries. SLA batteries require very precise three-stage charging in various constant current and constant voltage modes. Car battery chargers generally output very unregulated and imprecise voltages and will significantly shorten the life of a SLA battery. (Of course, if the car charger is a switched-mode unit designed to charge SLA batteries, you'll be fine). You might be OK to do it once, but certainly don't do it regularly.If you have a current limited lab power supply, you can charge the battery from that. With the power supply disconnected from the battery, set the PSU to 14.6V and 2A. Apply to battery. When the current has fallen to 100mA, set the power supply to 13.8V. When the current has further fallen to about 20mA, set the PSU to 13.2V and leave connected for as long as you like. There are normally specific values for voltages and currents in the datasheet for the battery, but these generic values often work well.

author: edy
author_rank: Super Contributor
timestamp: January 07, 2014, 03:55:37 pm
content: Thanks so much for all the help! Here's an update on what I did:I ended up plugging the new 12V 9Ah into my car battery charger to "top it up" (before I read the new posts)... it was only connected for 3 or 4 minutes and the charger indicated it charged fully (it shows a progress indicator and then green light). The battery was already reading >12V so the charger probably realized there was nothing to charge. The charger settings are 2A, 4A and 6A depending on battery size... I chose the smallest 2A which is probably still too high but it wasn't connected long, so hopefully I didn't damage anything. That is the last time I will ever plug it in a car battery charger thanks to the advice in the thread!I managed to disconnect the old battery completely from the alarm and hook in the new one. I was planning on that "parallel connection" trick but that was too difficult in practice since the clips on the battery were covered in insulation, I would not be able to keep the circuit intact without starting to strip wires and splicing stuff in. Just not worth the trouble, and thanks to advice on the thread, it seems it is not an issue. The alarm system didn't seem to complain.So now I have the OLD battery in my hand and measuring the voltage I am getting 13.11V !!! Huh? Even my new "12V" battery wasn't that high. I'm not sure then what is going on. Could the battery have been ok all along? I know we had a power-failure a few weeks ago and perhaps it is not putting out enough current for the time the alarm was out of mains power, and so it signaled the battery-failure in the alarm.Is there any way to test this? I tried the following....I hooked up my multimeter in SERIES to short the old battery... using the 10A setting, and it read 0.16. That looks like 160 mA, so next I switched to the 200mA range.... It starts around 180mA and then quickly drops down to about 140mA and after another 20 seconds it is below 100mA. Is that regular behaviour for any shorted battery through a multimeter? Then when I checked the voltage I am now getting 12.91V. So that exercise in checking the amps just dropped the voltage from 13.11 to 12.91 V.Does that look like a dead or dying battery?

author: SeanB
author_rank: Super Contributor
timestamp: January 07, 2014, 04:56:05 pm
content: Dead battery, cells have cooked off all the water so have gone close to open circuit. If it was good and you connected a meter on 10A range across it you would have melted the leads and the meter in about 1 second. Please do not try that again, a SLA battery can start a small bike, where the starter draws around 200A with no problems. The current ranges on any multimeter are designed to have a very low resistance, and the cheaper ones are unfused, the more expensive ones use a fuse that is expensive if you blow it for no reason. Next time use a 21W stop lamp to test the battery, if it cannot light it to full brightness and keep it lit for 2 minutes it is toast.

author: edy
author_rank: Super Contributor
timestamp: January 07, 2014, 05:41:16 pm
content: Thanks for the advice!Yes I found that out the HARD WAY when I was a complete *IDIOT*and decided to check the terminals on the 12V battery when it was being charged by the car battery-charger using the multimeter.... BUT instead of checking the voltage across the battery (placed the multimeter in parallel across the 12V battery leads while it was also clipped onto the charger).... I had the multimeter set to measure AMPs on the 10A.Needless to say, I saw some sparks and my charger clicked off.... must have detected the short and shut down. My multimeter survived the event, and so did the battery. A few seconds later the charger clicked back on and everything back to normal.

author: Unknown
author_rank: Unknown
timestamp: January 07, 2014, 06:09:08 pm
content: As I say above, 3-5 Years is about the maximum life for a standard SLA battery in your alarm panel. Beyond that time it is a lottery as to whether it sort of works, or just fails when called upon or melts the charging circuit on the board.

author: mrkev
author_rank: Regular Contributor
timestamp: January 07, 2014, 07:54:24 pm
content: This is kind of like list, of what NOT to doQuote from: edy on January 07, 2014, 03:55:37 pmYou were lucky that your car battery charger is not the classic cheap version... Usually, there is just voltage without any logic and/or current limiting, so it could end up badly. As we sell these SLA batteries in shop, I've seen one popped (customer tried to return it), it looked like a small barell...Quote from: edy on January 07, 2014, 03:55:37 pmWe are glad that you didn't try that "parallel connection"... You could destroy the new battery and even stuff around...Quote from: edy on January 07, 2014, 03:55:37 pmYou should measure with some load. Even something like 500mA is OK, so next time use a +-20 ohm power resistor... The battery is dead and you are quite lucky that it is... If you shorted the new one, you could melt parts of your multimeter and test leads...

author: edy
author_rank: Super Contributor
timestamp: January 07, 2014, 08:14:00 pm
content: Looks like I was not so lucky after all...Multimeter measures Voltage OK, and still measures AMPs in the 10A selector range (which uses the separate test lead hole marked 10A max) but when I am using the main test-lead hole which combines V-omega-MA and is limited to 200mA, the 200 microA-200mA range selector now shows 0.00 for all settings!!!! Argh!!!!There must have been a spike over 200mA even though previously my dead old battery was showing under 0.20 on the 10A selector and I noticed it hovering around 150mA. The spike fried my multimeter. I can still see my currents but now only at a resolution of 10mA (0.00 A display on the 10A selector). Can't get any more precise than that. I wonder if there is anything inside that I can fix or is this a lost cause?By the way, it is a cheapie "one-hung-low" (As Dave calls it) multimeter no-name brand called DVM810 (I have a better one I use anyways). Looks like this but without any branding at all:http://www.tequipment.net/VellemanDVM810.htmlPS - I found the manual and it looks like there is a 200mA/250V fuse that is the culprit:http://www.tequipment.net/assets/1/26/Documents/velleman/velleman_dvm810_manual.pdf

author: SeanB
author_rank: Super Contributor
timestamp: January 07, 2014, 08:27:20 pm
content: Well, a cheap 5mm fuse will get it running again, but hopefully this is a lesson learned. At least this fuse is cheap and easy to get. At least you did not do something to an expensive meter, this one is a pretty common low cost one. I have had some where a new battery was actually more expensive than the meter itself new.

author: nihilism
author_rank: Regular Contributor
timestamp: January 08, 2014, 02:53:56 pm
content: You know what this means, don't you?You need to watch more of Dave's videos!I'm sure there are a few where he shows how to measure voltage and current with a multimeter.