I need a fixed emergency light that will run for more than 90 minutes. Preferably 10 many hours, like all night. 90 minutes must be the industry standard for these things and they only have a 1000mAH battery and nicads. There are 100’s of this sort but they are all have the same specs and cheesy batteries. I suppose I could add a bigger battery but then the charging circuit would be way under powered and I’d rather go with Li batteries anyway.
I could design something or hack a solar outside light but I would prefer just to buy something if available. Need perhaps a couple hundred lumens x 10 hours.
Those units provide 90 minutes of light because that’s typically more than enough to evac a building. They used to be much larger with lead-acid batteries because of incandescent lamps; nowadays with LED the power requirements are reduced markedly.
How many lumens and how many hours?
Bleeding-edge LEDs are ~200 lumens/watt; more pedestrian/cheap models are ~100 lumens per watt. If you want a 60W incandescent equivalent that’s 800 lumens or 8 steady watts; over 10 hours you’ll need 80 watt-hours of storage if everything works perfectly.
A standard 2V 7.2AH alarm battery has some ~86 hours of capacity. But those care not for deep discharge and are rated at C/30 or some nonsense, so at 8W of discharge you’re going to get less than the 10.75 hours that simple math suggests.
Thanks, ESmith, for the calculations. Yeah, might have to roll my own. I think some of those solar outside lights are designed to run from dusk to dawn on the solar charge and they sense dark when the PV panel output drops off. Thus, I might be able to just wire a small, grid powered supply into the PV input.
When power fails, the unit will think the sun has gone down and begin to run all night if needed.
And another, somewhat related topic. This is going in two areas, a garage plus into an outside area where I want to be able to see my pseudo-transfer panel and start my generator.
I’m thinking of a clever way to monitor grid power while I’m transferred off grid and on generator. A simple lamp on the grid line would do. This would involve a non-code compliant tap directly into the bus before the main breaker. I’m using the main breaker already as part of a terribly non-compliant two part double throw switch to go on generator. So I guess I should not worry so much about compliance with code.
(I know . . . no lectures on this, please! I know all the risks and hazards! I’m going to upgrade to compliancy when I can afford to. This is a makeshift transfer panel for a farm area. It was either go cheap or go without.)
If you don’t need ~60W Incan equivalent, can live with a watt or two of LED light, and don’t care if the thing is on all the time, why not look at a USB charger+powerbank with passthrough power running a USB lamp or two?
Or simpler yet a power bank that defaults to power ports off whenever it detects shore power.
If you want more time for your emergency light, you can search on the web for emergency lights. There are models that allow you to add additional battery packs to extend the life. Many of this style have the light in one location and the batteries in a distant location.
The reason for the 90 minutes is the Life Safety Code put out by the National Fire Protection Association (NFPA) and adopted by most government jurisdictions as the local fire code… It is to allow a building to be evacuated as mentioned above. It also specifies the required lumens per square foot along the egress path to ensure people can actually see what is in the way.
Personally, for this application (if it were for my house) I would just put a cord on the emergency light for the 120VAC input and plug it into a regular UPS in a protected location. If your emergency light is LED, a modest UPS should power it all day. When the UPS runs down, it would then run off the internal battery for 90 minutes.
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