. Emergency Lighting has used SLA or Sealed Lead Acid which is rated for deep discharge.

Almost - Emergency Lighting uses sealed lead acid rated for long endurance on float charge and a relatively small number of deep discharge cycles. Golf Carts use sealed lead acid rated for repeated deep discharge but not endurance on float charge.

 

lets say we use a lead acid battery, and a power supply with a stable 13.5 volts

13V is too high.

@Ian0 I think the TS is looking at float voltage for a lead acid battery. 13.5 is a fairly good float voltage to maintain a 12V lead acid battery. Likely the TS is thinking of an SLA battery (Sealed Lead Acid for those who don't know). 12 volts is the nominal voltage. 2.1 volts is the full charge voltage per cell. Since there are six cells, 12.6 volts (not on a charger but fully charged) is an excellent voltage for an SLA battery. Same for a wet cell (car battery). 13.8 is the proper float charge - at least that's what I've been taught. Some will say 13.6. I'm happy enough with my truck when its battery is at 13.6 volts when the engine is idling. It shows a healthy charging system. When I turn the key on but don't yet start the truck, if I see a voltage of 12.2 volts (key on means electrics are on) then that's a healthy battery.

The TS wants to have a standby light source if the power fails. From description this is going to be a light that is on all the time. When power fails, the battery takes over. That's not a very good plan. There has been no mention of a switch to turn the light off during the day - but I'll assume that's in the plan. That would mean the switch would be before the light but after the battery. So that if during the day the power goes out and the light is off, no electrical energy is used. If power is still out after dark, the light can be turned on for some as yet unspecified time - it all depends on the battery being used and the light it's powering.

To be sure, there are as yet a lot of facts missing from solving this problem. I gather that the TS is attempting to formulate a solution to an anticipated problem. Here's how I'd go about having light if the power goes out: I'd start with a robust sized battery; something with many amp-hours of reserve power. That can be kept on a trickle charger so that if/when power goes out I have a source of power for lights. I'd start with this battery. It's a 12 volt SLA Deep Cycle (AGM) battery. It has 35Ah rating; meaning it can deliver 35 amps for 1 hour (respectively, though actual performance will likely be less, depending on conditions and temperature). I can- in theory - light 35 lamps that draw 1 amp per hour. Or I can light 7 lights that draw 5 amps per hour. Or any combination therein where the amp hour rating is used by the number of amps per hour I draw.

I would keep the battery on a standby charger (trickle) so that it's ready when I need it. Then - WHEN I need it I'd plug it into a lamp that has a 12 volt lamp. Automotive turn signal lamps generally draw 35 watts. Watts is not the same as amps. Watts is amps times voltage. So amps would be wattage divided by voltage. In this case 35W ÷ 12 volts is 2.92 amps. I could light one of these lamps (incandescent type) for almost 12 hours. Longer if I used LED lamps. Here's one that is low power; uses 0.4 watts (33mA per hour). Several of them to light up the house would be great. As for building a charger ? ? ? No, I'd opt for a smart charger, one that can trickle charge the battery without worry of damaging the battery either by failing to charge it sufficiently or over charging it.

It's not rocket science. Battery on a charger. When needed - plug in some low amperage LED bulbs. Use a switch to turn them on and off. When power is restored, put the battery back on the charger.

 

@Ian0 I think the TS is looking at float voltage for a lead acid battery. 13.5 is a fairly good float voltage to maintain a 12V lead acid battery. Likely the TS is thinking of an SLA battery (Sealed Lead Acid for those who don't know). 12 volts is the nominal voltage. 2.1 volts is the full charge voltage per cell. Since there are six cells, 12.6 volts (not on a charger but fully charged) is an excellent voltage for an SLA battery. Same for a wet cell (car battery). 13.8 is the proper float charge - at least that's what I've been taught. Some will say 13.6. I'm happy enough with my truck when its battery is at 13.6 volts when the engine is idling. It shows a healthy charging system. When I turn the key on but don't yet start the truck, if I see a voltage of 12.2 volts (key on means electrics are on) then that's a healthy battery.

The TS wants to have a standby light source if the power fails. From description this is going to be a light that is on all the time. When power fails, the battery takes over. That's not a very good plan. There has been no mention of a switch to turn the light off during the day - but I'll assume that's in the plan. That would mean the switch would be before the light but after the battery. So that if during the day the power goes out and the light is off, no electrical energy is used. If power is still out after dark, the light can be turned on for some as yet unspecified time - it all depends on the battery being used and the light it's powering.

To be sure, there are as yet a lot of facts missing from solving this problem. I gather that the TS is attempting to formulate a solution to an anticipated problem. Here's how I'd go about having light if the power goes out: I'd start with a robust sized battery; something with many amp-hours of reserve power. That can be kept on a trickle charger so that if/when power goes out I have a source of power for lights. I'd start with this battery. It's a 12 volt SLA Deep Cycle (AGM) battery. It has 35Ah rating; meaning it can deliver 35 amps for 1 hour (respectively, though actual performance will likely be less, depending on conditions and temperature). I can- in theory - light 35 lamps that draw 1 amp per hour. Or I can light 7 lights that draw 5 amps per hour. Or any combination therein where the amp hour rating is used by the number of amps per hour I draw.

I would keep the battery on a standby charger (trickle) so that it's ready when I need it. Then - WHEN I need it I'd plug it into a lamp that has a 12 volt lamp. Automotive turn signal lamps generally draw 35 watts. Watts is not the same as amps. Watts is amps times voltage. So amps would be wattage divided by voltage. In this case 35W ÷ 12 volts is 2.92 amps. I could light one of these lamps (incandescent type) for almost 12 hours. Longer if I used LED lamps. Here's one that is low power; uses 0.4 watts (33mA per hour). Several of them to light up the house would be great. As for building a charger ? ? ? No, I'd opt for a smart charger, one that can trickle charge the battery without worry of damaging the battery either by failing to charge it sufficiently or over charging it.

It's not rocket science. Battery on a charger. When needed - plug in some low amperage LED bulbs. Use a switch to turn them on and off. When power is restored, put the battery back on the charger.

Hey tony, since you brought up chargers, ive seen old school ones only had a transformer and a rectifier, seems what made those chargers smart was the designed output. Using that information, it would seem we would not need a modern day charger circuit, which would appear not only more complicated than it needs to be, but also more expensive than it needs to be. It seems the basic drawing i added to my posted question will work as long as the power supply is designed to not exceed the voltage of a fully charged lead acid battery. I could add a switch, which is always in the off position between the battery and light bulb, like you mentioned, but i am more interested in learning a working model for the design i drew up, for this post. It seems from what people are saying, there would need to be something added to prevent the light from discharging the battery too deeply. But, i am more interested in the simplest version, which seems would be to have led's in series as the auto-off switch and the light. What do you think about this?

 

@Ian0 I think the TS is looking at float voltage for a lead acid battery. 13.5 is a fairly good float voltage to maintain

13.5V is not bad, maybe a little low, recommendations vary from manufacturer to manufacturer, but he had written 14V when I quoted him (and must have subsequently edited it) and 14V for float would be too high. Yuasa published a graph of life vs. float voltage.

From description this is going to be a light that is on all the time. When power fails, the battery takes over. That's not a very good plan

That's absolutely standard for a "maintained" luminaire.

 

it would seem we would not need a modern day charger circuit,

What you save on the charger, you will waste on replacing damaged batteries. The float voltage needs to be temperature compensated and maintained accurately down to tens of millivolts. Yuasa quotes 2.275V±5mV per cell.
This is the graph of float-voltage vs. life.

 

Hey tony, since you brought up chargers, ive seen old school ones only had a transformer and a rectifier,

Have you looked up any of the DIY schematic designs that Both myself and reloadron mentioned?

 

Have you looked up any of the DIY schematic designs that Both myself and reloadron mentioned?

Heres one i found, which is basically what i described in my posted question. Cept it has some caps and a led light to let the person know it has power. Just like the old school chargers, i dont see anything extra. Yet they worked. Is there something you are trying to say that isnt visible in the schematic or when looking at the inside of an oldschool battery charger that has a purpose related to charging a battery safely that i didnt see?

 

.... Yet they worked...

They worked, in a rough and ready sense, and depended on being closely monitored in use. A charger such as that will supply it's maximum current to the flat battery irrespective of how appropriate that level of current is (too high? too low?), and as the battery fills and the voltage rises it will gas the electrolyte away. It is not a circuit for unattended use, and depends on being disconnected when gassing starts.

A modern three-stage charger matched to the battery size will optimise the charge rate, maximise the delivered charge, and maximise battery life. They don't cost too much either. But if a hobby version is required the LM317 circuit above provides a reasonable approximation to the charge profile for lead-acid cells.

 

They worked, in a rough and ready sense, and depended on being closely monitored in use. A charger such as that will supply it's maximum current to the flat battery irrespective of how appropriate that level of current is (too high? too low?), and as the battery fills and the voltage rises it will gas the electrolyte away. It is not a circuit for unattended use, and depends on being disconnected when gassing starts.

A modern three-stage charger matched to the battery size will optimise the charge rate, maximise the delivered charge, and maximise battery life. They don't cost too much either. But if a hobby version is required the LM317 circuit above provides a reasonable approximation to the charge profile for lead-acid cells.

Ok, noted. What is the cheapest, simplest improvement you would suggest to add to a circuit with just a transformer and rectifier to be able to be deemed "unattended worthy" (aka plug it in and forget it worthy)?

 

What is the cheapest, simplest improvement you would suggest...

Adding something along the lines of the LM317 above is the simplest I know. Not as good as a proper three-stage, but close.

 

What is the cheapest, simplest improvement you would suggest to add to a circuit with just a transformer and rectifier to be able to be deemed "unattended worthy" (aka plug it in and forget it worthy)?

The circuit @MrChips suggested in Post #17

 

13.5V is not bad, maybe a little low, recommendations vary from manufacturer to manufacturer, but he had written 14V when I quoted him (and must have subsequently edited it) and 14V for float would be too high. Yuasa published a graph of life vs. float voltage.

That's absolutely standard for a "maintained" luminaire.

Yes, 13.5 is slightly below recommended float. IF the TS edited his statement from 14V down - I didn't see it. And yes, 14V IS too high for a float. It will heat the battery and boil the electrolyte. The battery will fail sooner than later.

If the light is to remain on all the time, which I believe I read the TS saying that the light will be switched on and off, - um - well, sort'a self explanatory.

As for the transformer / rectifier chargers of old, those were not meant to be used all the time. You connect them over night, then take them off in the morning. That was good enough in the olden days, but certainly not recommended for trickle charging. The next generation of chargers had a switch where you could select trickle charging; however, I don't have any information on how they were constructed. Modern chargers are likely chip controlled; since I've never taken one apart, I don't know that for sure. But it seems likely. The reason - as others have already said - is to optimize the charging of the battery while not sacrificing its useful lifetime.

Stepping away from SLA's and wet cell car batteries, there are lithium based batteries. Here's an example of why you don't use a dumb charger on those. I know this is a little off topic, but it's well worthy of being stated that if you charge a lithium battery with too much current you will have an explosion. Let me reiterate that part - YOU WILL HAVE AN EXPLOSION! Lithium has a very specific charge profile. Exceeding that profile means destruction of battery and equipment. Possibly losing the entire building to fire. Unlike SLA's, Lithium's are also sensitive to low voltages. Take them too low and they begin to build dendrites that can short the cell. And since they are capable of liberating their energy stock quickly - they CAN get hot and they CAN start a fire. I've had lithium batteries go below their safe voltage and had one get warm, but never hot. And I've never had a fire. However, since that IS a distinct possibility I don't keep old lithium batteries that don't hold a charge laying around. They're just too dangerous. And that's why the post office requires you to declare when lithium batteries are being shipped. Air freight and commercial transportation doesn't want lithium batteries in their cargo holds either. Again, fire is a bad thing. Especially at 35,000 feet altitude.

Back to SLA's: I have had a few go bad sitting on the shelf. They were charged when I put them there but over time their voltage has leaked down. Having leaked down they sulfated; sulfate buildup on their plates. Though they show full voltage after being charged, their capacity is almost completely gone. I've had to toss batteries from not being regularly charged. Car batteries are a little better because they're wet cell; still, they can suffer the same fate. That's why we've asked so vehemently about what battery or batteries you're planning on using. The type of battery and the charge profile are critical. And in most cases low voltage is also something that needs to be seriously considered. Running a lamp until the battery is dead is an excellent way to shorten the life of the battery; again, assuming SLA's, not lithium.

 

I know you mentioned a 12 Volt 4.0 Amp adapter. What will your maximum actual load be?

Long ago before I retired I worked in a secured facility. Plenty of assorted cypher locks which were needed in a power failure until our backup generator came online. When the old systems were being gutted I noticed the main control panels had backup. They used Altronix systems with a SLA battery. The supplies are still around and seeing some on Amazon relatively inexpensive. Then too it depends on what you consider expensive? Anyway here is an example of an Altronix LPS3 which will support a 2.5 ADC continuous load. Designed to support the load and switch instantly on a power failure. The only additional part is a simple transformer. The voltages are switch selectable 6, 12, or 24 VDC out. The manual can be found here. They also make higher current units like the SMP5 versions. These are a simple turn key solution to what it seems you want to do. Just add a SLA battery and basic transformer, they work on an AC input so all of that is done for you.

Ron

 

That's a good summary, @Tonyr1084 . I had a friend who overcharged a lithium battery, and he burned down his uPVC conservatory. It was only a small conservatory but the smoke damage to the rest of the house was awful.
I'm not sure all the old lead-acid chargers circuits were so dumb. I think in some cases the transformers were clever even if the electronics weren't. I think there were leakage reactance transformers to limit the current, and ferroresonant transformers to regulate the voltage (we had a conversation about them a couple of months back). I can't help thinking that these days we'd call them "smart transformers"! After that came thyristor-based controlled rectifiers.

 

Ok, noted. What is the cheapest, simplest improvement you would suggest to add to a circuit with just a transformer and rectifier to be able to be deemed "unattended worthy" (aka plug it in and forget it worthy)?

Generally, you might have a "replacement plan". e.g. replace every 3 years.

I designed a safety system with a 24 VDC battery backup from AlarmSAF and the next think you know, the bean counter" wants to" configure it to not use batteries to "save money".
False alarms, "e,g" strobes might be a possibility without the backup.

You would have no strobes in an unsafe condition until the generator kicked in about 2 minutes later.

Now, what if the generator didn't start?

--

I got a surplus ` UPS and I took a chance that it was just a battery. It was.

I think it has a buzzer, but I can't hear it. It's under the bed. Tinnitus at 2600Hz doesn't help.

I did have a failure recently. There is an answering machine on the UPS, so I would know if the UPS failed and there was a power failure, but not battery failure. It's necessary for the cordless phone system.

Now, probably, I could configure say a Rasberry PI and the NUT software to say email battery condition. It might even help if I got some extra wiring in that room and connected to the UPS via a serial server. I would not mind an email if the UPS battery was low.

I have to get the UPS connected to my Network stuff and my NAS with the shutdown software.
The new control board for my APC UPS is, I think, more expensive than the UPS itself.

I really need some sort of comprehensive monitoring system in the house falling under:
==== the full supervision, low batter, alarm and low power would be really nice

1. Water leaks
2. Water infiltration
3. Door prop: (we lost too much food)
1a) Refrigerator/freezers
1b) Shed left open 1hour after sunset
4. Temperature
refrigerator/freezers
==== I could use an interface to a local alarm
==== with low battery as well
5. UPS batteries

I can probably think of more stuff.

I started on some of the projects, but sometimes I implemented them and they are so cheap they break.

Water alarms
Broken - only indicates in the bedroom, 4 channel wireless, no low battery
Had that alarm on a piece of plexiglass sitting in a french drain. Water infiltration.
It can be handled with a wet vac.

An alarm on a window sill - You can't hear it. What good is that?

I see the usefullness of a whole house shut-off too.

Door prop
I have parts to start that project. I have two door prop commercial alarms that are loud.
I have the switches that I want to install. They can add up to a 10lb pull to the door and this would be really good.
So, I have to cut, tap and mount these. That would be an immediate help.

One vintage fridge/freezer needs work on the inner freezer door. It melted when a hair dryer was used to defrost the fridge. It needs to be straightened out.

I'd also use the door prop alarm to turn on external lighting. A wall-mounted lamp that is usually turned on when yur in the fridge.

A door prop alarm for the shed. That one would be 1 hour after dark and door left open. I usually put tools away late at night. It could use lighting too.

Temperature/Fridge
I have a alarm with history from Thermoworks, but the wires are too thick and the magnets are not strong enough.
I put the refrigerator alarm in the fridge/freezer and the freezer alarm in the freezer.
I'd like to:
1. use a flat cable that's usually used for LED's
2. Build an interfacable low-battery output
3. Build an interfacable alarm a output.

Washer/Dryer stopped would be useful, but not important right now.
Now I set a mechanical timer for 20 minutes for the washer and similarly for the dryer.


Comprehensive alarms
Monnit looks pretty neat
So, does Zigbee and maybe HomeSeer.

But there is just so much other stuff that needs to be done.

I have some serial servers (up to 16 port), not hooked up yet, that can do wierd stuff with two of the handshake lines on the serial port. It can generate an email on change of state or goto high and goto low which is cool.
So, I could generate a TXT message or an email in theory.

Water alarms need to be instantaneous.

What I'm saying is you can't rely on a battery that isn't supervised.

 

I designed a safety system with a 24 VDC battery backup from AlarmSAF

I have one of these low current AlarmSaf boards laying around. Bring back any memories?



Ron

 

Idk if you all get an email when i post this, but, i wanted to be courteous and do so by saying what i learned here. Before i posted this question i didnt know as much as i do now. I learned batteries are actually dangerous. I learned somewhat how they used to charge batteries and how they do now. I learned i can have a battery in a circuit essentially indefinitely so long as the voltage is set right. i learned this forum is a place where actual people help actual people. This experience made me rethink my simple design and wonder about things such as what would be an actual good way to not just power a light bulb, but to be energy self sufficient, meaning, how would i power my own life, what would truly be a wise and clean way of doing it, and what way would actually work long term and have the least maintenance. After this experience, batteries seem like a bad choice to power life. Anyone have any alternatives to replace the battery in the simple circuit we are all here talking about?

 

After this experience, batteries seem like a bad choice to power life. Anyone have any alternatives to replace the battery in the simple circuit we are all here talking about?

Powering life? Batteries only work well for the energizer bunny. I figure life is powered by life around us and knowledge.

As to alternatives to batteries? Depends on exactly what you are looking to do? Pretty sure you have seen emergency lighting in things like stairwells to light a way when mains power fails. The application determines how something is designed and built.

Ron

 

This is the requirements for PM/ITM per NFPA.
https://www.nfpa.org/News-and-Resea.../2020/July-August-2020/In-Compliance/NFPA-101

 

I have one of these low current AlarmSaf boards laying around. Bring back any memories?

I don't know.

The power supply was pretty complex, but did use a linear regulator. They have to use switching regulators now to get quiescent power lower per regulations.

A bunch of PTC protected class II circuits with a bunch of enables/disables for fire alarm panel and integrated access control power.

It actually turned out to be very useful because of the strobes. High inrush and the manufacturer started to make a low inrush version which we needed.