POWER FAILURE LIGHT

I'm planning to build a power failure light with the following characteristics:

> Automatically turns on
> LED lighting
> Rechargeable Batteries
> Minimum 2 DAY run time

This light would ned to be sufficently bright enough to light up a 20x20 room. The light just needs to be sufficently bright enough to walk around and socialize safely.

Anyone got any circuit ideas?

Shouldn't bee toooooo hard. I'd start with a 12V Gel Cell. I'd add a solar panel too (small one) then you could charge the battery durring the day turning 2 day runtime into virtually infinite.

I made a system similar to what Saaby suggested but opted for a 110 trickle charger for the gell battery. Solar is much more problematic and more expensive than a cheap regulated trickle charger. I installed a relay on my house current that is normally open and will close in the event of a power outage. I installed a switch up stream of this relay so I can disconnect the 110 keeping this relay open; in otherwords over ride the relay and turn the lights on even if house current is available. I also installed a switch on the 12 volt side so I can turn the lights off in the event of a power outage. There is no reason to drain the battery with the lights on during daytime hours. Two day run time is simply a function of choosing the correct capacity of the battery to match the current draw of your LED system.

I have since installed and integrated a full 12 volt LED light system but I still have some *dedicated* emergency lights that will come on in the event of a power outage. I installed a 12 volt photo sensative switch which in turn activates a 30 amp automotive relay. This 30 amp relay controls all of my LED lighting and the relay is open during daylight hours.

- Don

Funny, I just ordered some parts to begin experimenting with exactly this kind of thing this afternoon.

If you choose a gell cell then charging is relatively simple, at least it would appear so from what I'm hearing around here and reading. If you have a 12v gell cell you need to supply 13.8v to it and it will regulate it's own current, so that is not terribly important. This is a float charge and a gell cell will last for years in this state.

If size considerations are more of an issue you can also trickle charge Nicads, but I'm not sure about NiMh's yet. You would trickle charge a nicad at a C/50 rate, so for a 1000Mah pack at 3.6v you would apply 20ma, which incidentally is exactly the same current you would need to run a white LED. So I'm experimenting with this combination next. Using a non-polarized .47uF cap to bring 110v down to something reasonable (like the LED nightlights in another thread) and also using that current to trickle the nicads.

I would like to avoid having a relay in the system that would need to be energized all the time by the house current. This would be the easy way to switch on the light when the power was out, but I feel like I should be able to get by with a simple diode to keep the power from going down the lines and trying to run the rest of the neighborhood off my batts I haven't gotten that far yet though.

I will also be building a CDS cell/transistor circuit in to turn it on only when it's dark in the room. So it would light in the dark whether the power was on or not.

I have some research to do on the battery charging part yet. I'm not 100% sure what all will be necessary to do it safely and in a way that preserves the battery for the longest amount of time. So I'll be following this thread too.

Thanks,
James

I also just realized that if you can't get a Gel Cell large enough, or want more runtime or what not you could get a few batteries (Not necessarily Gel Cells I guess) and wire them in parallel...

Saaby,

You are correct about wiring them in parallel but I believe you can get Gells up do 8D size if you are willing to pay the price!

- Don

Check into the TRACE ENGINEERING C-12 controller, it does the charging and the "night light" mode which you use to run your lights

I am using two of them on this project:

http://www.tri-met.org/max/yellowline/stationart/rosequarterart.htm

Which is basically, going to be a 500-600 LED "Nite Light" for a light rail station for Portland

Mike
www.inretech.com

Originally posted by McGizmo:
Saaby,

You are correct about wiring them in parallel but I believe you can get Gells up do 8D size if you are willing to pay the price!

- Don

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<font size="2" face="Verdana, Arial">Ah...but if Gel Cells are one of those rare but freaky things where you pay a premium for extra capacity...IE with Hard Drives the more capacity you buy the lower the cost per MB--if Gel Cells AERN'T like this...AERN'T

I've never priced gell cells, but sealed lead acid batts are very similar and not very expensive. You can get a 2AH 12v for under 10 bucks, and a 5AH one for $15. 5AH would run lots of LED's for a long time! they aren't that big, 3.5"x2.7"x4" for the 5AH version. And they can certainly be wired in series or parallel.

-James

Saaby,

There is an economy of scale but once you get to automotive or marine sized batteries, you cn buy a dep cycle lead acid battery for a lot less than a gell. A 200 aH 8D prevailer could cost you close to $400!

- Don

BTW, That's a bunch of LED's for a bunch of hours! If someone is really serious about a large scale LED light system, 24 volt should be considered; expecially if there are long wire runs. Copper is expensive and you can save on wire size.

If you want REALLY big SLA/Gel-cells (very similar in function, one uses gelled electrolyte, the other a 'damp' nylon or fiberglass separator between the plates) check this link- http://www.dcbattery.com/rolls.html

Brock posted about his extraordinary power failure light system, but I don't recall where or when. I just searched under "Brock power failure" in Homemade and Modified lights and came up dry. I hope he notices this thread and posts.

Brightnorm

If you plan on making a big system (3+ floors, true usable light instead of 'I can see the door' lights) you may want to simply invest in a standby generator, if only to charge the batteries. A nice propane-fueled 2.3kw generator and a small tank (small HOUSEHOLD tank, not a grill tank) will let you keep the LED lights running for weeks.

Well my system is a bit overkill, but that is just the way I am. I have 8 Trojan T125's (about 12kw worth), and two Trace 2500w sine wave inverters to feed my system. I have a bunch of 12v CF's around the house and about 1/4 of my outlets are powered by the inverters (they are mounted upside down from the "grid" outlets). I have 4 lights (cf's) that automatically come on when the grid fails near the staircases, but they can also be turned off manually. I keep the batteries charged with 4 Siemens SP75's solar panels and a Solar Boost charge controller.

So I either have a really big power failure lighting system or a small solar setup (RE). I can run my fridge and chest freezer and some other essentials about 3 days without power, much longer with sun or one of my 2 back gensets, or I can even charge by battery bank from a car idling outside, all wired and fused.

Brock - you're a nut after my own heart. Imagine what you could do with an EV full of 36Ah's at 380V! There's a bit of backup battery for you.

Originally posted by James S:
If size considerations are more of an issue you can also trickle charge Nicads, but I'm not sure about NiMh's yet. You would trickle charge a nicad at a C/50 rate, so for a 1000Mah pack at 3.6v you would apply 20ma, So I'll be following this thread too. Thanks, James[/QB]

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<font size="2" face="Verdana, Arial">I was looking for info on trickle charging walkie-talkies. reading this I assume that NiCds are better than NiMhs in this respect? ie dumb (non regulated) overcharging.