Go BottomSecurity system batteries during power outages
 | kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon 
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2003-08-04 60928
AC5ZO's comment about 6 volt golf cart batteries in another thread got me to thinking about our security system batteries. I'm hoping that somebody with home power systems or savvy radio operator (hint hint AC5ZO) can help me out here.
It seems that some (*&^%() thief in our area has found that rural homes are often easy picking for burglary. We haven't been broken into, probably because I am here most all the time since I work at home, but the guy down the road was hit a week ago.
To compound the problem we have fairly frequent power outages, and Murphy's law dictates that the outages occur when we're on vacation. We were gone for 10 days last Christmas, and we had a 5-day outage during that our trip.
We have a backup generator that we can run for a few hours each day to keep the food frozen. I am building a system to be able to dial-in to the house and start and stop the generator over the telephone and through our security system.
The problem is that for outages longer than around 12 hours our security system batteries die. Propane is too expensive to run the generator 24 hours a day just to supply the 1.5 amps that the security system needs.
I want to hook up two or three Optima deep cycle batteries (minimal outgassing) to power the security system. The problem is that these batteries will be on their own charger and I don't want the voltage from this charger to backfeed the security panel. So I need to hook up a diode of some sort to keep that from happening, and I want to get it hooked up without damaging the security panel, batteries, or battery charger in the process.
Any ideas? Does anyone here know of an off-the-shelf solution that I can use for this?
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 | AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144 
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2003-08-04 60932
We can discuss this here, or you may email me at
ac5zo(at)yahoo.com
I do not know what you mean exactly about the battery charger backfeeding the security panel.
Most security panels have a small gelcell that can keep it powered for four or five hours. It has its own onboard charger that powers the security system when the AC line is working properly.
What I expect that you want to do is to have the Optima batteries being charged with their own charger and then connect the batteries to the security system. If that is the case, then you may use a diode from the optima batteries to the gelcell. If you lose AC power, both the charger for the optima batteries and the charger in the security system will go down at the same time. The gelcell in the security system will supply power for the alarm system until its voltage get 0.6 volts lower than the optima batteries and then power will be delivered from the optima batteries through the same circuit that pulls power from the gelcell.
When the AC power comes back on, both chargers will start to operate, but the security system charger will only charge the gelcell and not the optima batteries because of the diode. The optima batteries will charge with their own charger.
Sometimes the 0.6 VDC drop cannot be tolerated. If that is the case, you can put a 115VAC relay that is always powered on by the AC line. If the power fails, the relay relaxes and closes the NC contacts connecting the optima batteries to the gelcell. When the power comes back on, the relay will pull in and separate the optima batteries from the alarm power circuit.
For figuring the AH capacity of the battery, just multiply the amperage draw times the amount of time that you want standby power. This works for really light loads on batteries where you are expecting 100+ hours of power. So, if you want 100 hours of standby, you will need about 150 AH worth of the Optima batteries wired in parallel. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-04 60937
Thanks very much for the info. You nailed what I want to do with the batteries, but there are some niggling details I don't understand. I'll take you up on your offer and contact you via email.
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-04 60959
I'd like to publicly thank AC5ZO for helping me out with my battery dilema. He has been generous with his time and answered all my questions thoroughly.
TractorPoint folks are the BEST! ....
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 | Misenplace
Join Date: Jul 2003 Posts: 875 Michigan
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2003-08-05 60967
You might look inside the main panel of your system. I recently discovered that I have gel cel backup batteries with a built in charger. I say discovered because the alarm would not stop beeping. I took the panel apart and found theese batteries that look like a motorcycle battery, only smaller. It was a bugger finding replacements. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 60981
Yes, the panel has two 12V 7AH gel cell batteries wired in parallel. During an outage they only last 12 hours or so, and therein lies the problem. I'd like at least a week of backup power.
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 60982
I have worked on a number of security systems and they all used fairly standard gelcell batteries. The brand is not very important but the voltage is. Most are 12 VDC.
Get a battery that will fit and has at least the same AmpHour capacity as the previous battery. A small increase in AH capacity will not hurt if the battery will fit. Going much over the original AH capacity might strain the internal charging circuits.
If your system has a lead acid gelcell, stay with lead acid technology including gelcells, or non-vented, or starved electrolyte. Brand does not matter.
There could be some systems out there that use NiCads and you must stick with them. You can substitute NiMH if you cannot find NiCads, but do not substitute gelcells.
KW has gelcells in his alarm panel, but he wants to have backup power for many days rather than a few hours. ....
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| Misenplace
Join Date: Jul 2003 Posts: 875 Michigan
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2003-08-05 60987
kschumm, Do you have a generator or back up power ? As long as there is power to the circuit the system should charge. A few years ago I picked up a larger Generac for about $1300 that will power 90% of my home at one time.Its about 13 hp. I had the generc circuit board and plugs installed so it can be plugged in the garage. The Generac switch/circuit panel is by the main breaker. The boxes were about $500 and another $500 for an electrician but I made some very long runs to have everything exactly where I wanted. The Honda generators of similar size are about 1k more but a lot quieter. ....
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 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2003-08-05 60988
I was thinking that a solar panel as back up and battery maintainer might be preferable to a standard charger as it would provide some power when the house current is off.
Most of the commercial standby power systems are still vented lead acid, but I agree most of the valve regulated Lead acid batteries are better for this applications. The best for deep discharge are the flat plate AGM batteries as the plates are thicker and they have greater pressure on the plates to hold the oxides on the plates. Deka makes them among others. The Optima are essentually the same construction except they apply greater pressure and the plates are thinner as they are rolled. ....
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| Misenplace
Join Date: Jul 2003 Posts: 875 Michigan
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2003-08-05 60990
A number of folks who are building hunting cabins near our camp are useing a battery powered system by Onan. They use perhaps 12 of the optima batteries. The Generator comes on automatically when the batteries are low to charge them. Two camps down they buitl about 1200 sq' and this system powers the entire camp. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 60993
Doc, we have a 13.5 KW generator that is connected to the house through a transfer switch and fueled with a 1000 gallon propane tank. The basic problem is that it costs too much to run the security panel off the generator for seven days.
I computed the numbers once, and they are something like this. Assuming the tank holds 1000 gallons and is full when the power fails (big assumption) with a 30-40% load on the generator it would run about 5 days before running out of propane.
Now the downsides to using the generator. They only fill tanks to 80% capacity so we lost 20% of the runtime right there. Also, the odds are that the tank will only be half full when the power goes out, cutting runtime further by another 50%, so we're down to about two days of 24/7 operation.
Then you have cost - currently it costs about $1300 to fill the tank from empty. That kind of money will buy enough batteries to run the security system for a couple of weeks, and the batteries are reusable whereas the LP gas is gone.
So my plan during unattended outages is to run the generator a couple of hours a day through automated controls to keep the food frozen and use the batteries to keep the security system alive for a week or more at a time.
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 60994
Peters, thanks for the suggestion. I have thought of using a solar panel, but a battery charger is much less expensive and the batteries will get some charge when the generator runs to keep the food frozen. The worst case situation here is an unattended power outage during the winter, when NW days are short and clouds are thick. My instict tells me that a couple hours of charge when the generator is on will probably provide as much or more recharge current as a solar panel would during an entire winter day. And if snow is on the ground the generator will work where a solar panel would not. I'm trying to design this system to cover the worst case scenario, which is usually not possible because something stupid always happens.
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 60995
Actually if you have the Optima battery setup that we talked about, they could have a significant amount of recharge during the two hours of generator time. So, the system will probably last quite a bit longer than the basic AH rating of the batteries. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 60997
I really like the hunting cabin approach, but that's probably a lot more money than a few Optima batteries and a battery charger. Great for off-grid though.
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 60999
A typical charger will deliver between 6 to 10 amperes for a full tapering charger. It takes a pretty hefty solar panel setup to do that, and you also have to worry about them getting covered with dirt and snow. To properly charge batteries with a solar panel, you also need a voltage regulator or shunt regulator.
You can keep your Optima batteries charged with a voltage limited charger set to 13.8 VDC indefinitely. Such a setup could completely charge the batteries in a two hour period.
You have to be careful with regular chargers that can reach high voltages (16 VDC) under lighter loads because these can damage the batteries if left connected indefinitely. ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 61000
From an economic standpoint, it takes about twenty years to pay for off-grid solar power if you have regular power lines running to your property. It is another matter entirely if the cabin is remote or if power interuption is the norm.
New LED technology may just make the 12 DC cabin a practical reality. I have a little LED flashlight that runs for 200 hours on three AAA batteries. I already run my ham radio equipment off of 12 VDC, but the batteries are charged by the AC powerlines. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 61001
AC5ZO, I looked at battery chargers in the Northern catalog and a lot of them have the "auto-shutoff" feature but none of them mention the tapering charge feature. If a charger offeres a tapering charge capability would you expect them to mention it as a feature?
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 61005
An electronic auto-shutoff unit should work. They will generally monitor the voltage and come back on when necessary. I will look at the Northern site and email you some numbers to look at.
I have a charger with a mechanical timer that is OK for guaging the amount of charge put into a battery, but would not work well for your application. My other charger is tapering and autoshutoff. ....
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| Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2003-08-05 61006
You are correct a full Solar or DC system takes a while to pay off here if the line are local. The cost for the panels are decreasing and as the NiMH batteries from the hybrid traction motor are retire the equation will change.
A friend on mine manufactures solar cells in Toledo. Currently most of the production goes to the far east. I worked on cell phones for a while and in europe the phone system was so bad that cell technology was immediately adopted. Motorola was celling 10 phones in Europe to one here.
I wonder if we are also shooting ourselves in the foot as the solar technology is heading to India. If their cost for energy are near zero in 20 years it will be hard to compete with them on things like programing etc. ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 61008
KW, look at the Century 87151 Charger. You can buy it through Northern as part # 167751. It is automatic on/off and will charge at 15 amps which should do a good job bringing that bank of batteries back up to charge in a couple of hours.
This charger will put about 30 amp hours back into the batteries in 2 hours at full capacity. Your alarm system will use 44 AH in a day if it is on the AC line for 2 hours. At this usage/charge rate, you should be able to keep the alarm going for 20 days or longer with three Optima batteries and daily 2 hour charges. ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 61010
It occurred to me that this same system could keep your alarm going indefinitely with about three hours a day of charging even using a single Optima battery. More batteries would give extra reserve capacity if you needed it, but even a single battery should power the system for two to three days without recharging.
Of course if you miss a charging day, you have to make up the time later. ....
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| Misenplace
Join Date: Jul 2003 Posts: 875 Michigan
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2003-08-05 61014
Kw, you got me on that one. I never even heard of a propane generator. Mine takes 5 gallons of gas every 5 hours. Of course I dont run it 24/7 when the power is out. My thought was that the generator would charge the batteries enough to last the night if you ran the genset each day. The batteries system with shed is probably around 15k. Thats just a wild hair gues but a Onan diesel generator is a few xtra pennys. This system was deseigned in Northern Mi for all of the summer homes on islands. My camp is 5 miles from electric. My neighbors tried to get everyone to go for electricty this year but even at 5k per landowner theye couldnt get more than a few to agree. I personally dont want to see that much development in deer copuntry so the battery system is a good reliable and easy option. ....
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| AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144
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2003-08-05 61015
Dave, can you get propane delivered up there?
A lot of the really good automatic backup generators run or Propane or natural gas. These are packaged units with weather enclosures and are made for fixed installation. ....
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 61019
AC5ZO, thanks much for the info on the Century battery charger. At only $70 it's a deal.
I thought about buying fewer batteries and running the generator a bit longer to keep the system running indefinitely. There has to be a sweet spot of battery capacity vs. propane usage.
When the battery voltage drops below a threshold the security panel shuts itself off, but I don't (yet) know what that threshold is.
Since several people seem to be interested I will describe my project in a bit more detail.
Our transfer switch is manual. I bought a small industrial computer with a color touchscreen and some digital i/o (used to be a medical instrument), some OPTO-22 relay hardware, and a linear actuator off of ebay and I'm currently writing the software to automate the transfer switch. Doing it myself will give me much more flexibility than buying a canned solution. Among the features I will implement are automatic generator exercising, exercising on demand, automatic switchover on loss of AC power, and the ability to monitor and control the generator through a touch tone telephone interface via the security panel. The computer will also call me on my cell phone if any fault occurs.
I will interface to the transfer switch by monitoring the status LEDs with digital inputs and by running some controllable relays in parallel with the existing switches. Hooking the linear actuator up to move the contactor switch lever is fairly straightforward, and I will use limit switches as safeties on this.
It wouldn't be much more work to monitor the battery voltage and automatically turn the generator on when the battery voltage approaches some lower bound. That would probably provide the optimal propane vs. battery solution.
I'll post pictures when I get it all done. I'll probably have the only home transfer switch in town that has a gui touchscreen interface, ethernet, and is web-enabled!
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| kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-08-05 61020
Also, many gas engines can be converted to propane. Our generator has a Kohler 25hp gas engine that was converted by the manufacturer (Gillete Generators) to run on propane or natural gas.
I would have went with a natural gas generator if it was available up here. Propane is great for backup generators. You don't have to worry about stale fuel, it is delivered by truck, you can have BIG tanks of fuel, and it burns clean. For stationary standby type generators it's great, but if your generator gets tossed in the back of the truck for a trip to the woods gasoline or is probably better.
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| Misenplace
Join Date: Jul 2003 Posts: 875 Michigan
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2003-08-05 61021
Ac, you can get propane but its a bit of a pain. My property is the middle of 50k+ acres 31k of which are private. The road my property is on is a very nice road but 5 miles in from the public road where it is gated. My roads are gated as well. They will bring free tanks but to get them filled I would have to set out on the highway for god knows how long waiting for them to let them through the gate. Most camps are useing 50# cylinders and takeing them in to town for refills every couple of days. This is not a problem for most. I am at my property often but many only show up for deer season and usually then only for a week. ....
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 | Chief
Join Date: Jul 2003 Posts: 4297 Southwest MiddleTennessee
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2003-08-05 61022
Oil stays alot cleaner in a propane powered generator as well. Makes it last alot longer. ....
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