Lighting up a Salt Lamp without electricity?

April 25, 2009 7:41 PM

Looking to power (light) a Himalayan Salt Lamp for about 48 hours, without using an outlet.

My friends and I play in a Live RPG, where we will set up in a campsite that does not always have electricity available. One of the decorations we'd like to use are Himalayan Salt Lamps in various forms - some as lighting, some as props.

I have several lamps that run off a standard Nightlight Bulb, and have a power cord to plug into an outlet, but I don't have a power source. Ideally, they should be able to run for 48 hours straight, although 24 hours would be OK (Only at night, or when in use). The cord has a snap mechanism to hold it into the lamp, so if I were to use a different power source, I'd need to replace the holding mechanism or find a new one.

I was thinking a computer UPS, but I don't know the power usage / metrics to figure out the one I need to last that long. It would be one lamp per battery / location.

posted by GJSchaller to technology (12 comments total)

Would a led tea light work? It runs on batteries, these flicker like a candle flame.
posted by JujuB at 7:56 PM on April 25

A quick Google search for nightlight bulbs suggests the incandescent variety tend to be around 4 watts. So you're going to need 4w x 48 hours = 192 watt-hours per lamp. So theoretically something like a 16 amp-hour, 12 volt battery needs to be inside your power source, and realistically more like 20-25 amp-hours. That's a fairly big battery, 15-20 pounds probably.

You will probably have better luck with those portable power boxes that combine a battery and an inverter in a portable package. Technically they aren't all that different from a UPS running on battery power, but they are designed for this type of scenario specifically. Many UPSes I've seen won't power up without being plugged into a working outlet--though of course they'll stay on if power is disconnected once they're on.

Here's an example of this kind of product. Not a recommendation, just an example. They are kind of expensive but perhaps can be had cheaper elsewhere. If you can stand the noise, a little 2-stroke generator and a bunch of extension cords will probably be a lot cheaper than trying to do this with batteries.
posted by FishBike at 8:13 PM on April 25

You could take the bulbs out and replace them with little LED keychain flashlights, assuming there's room and you don't need these to be very bright.
posted by waxboy at 8:34 PM on April 25

Have you considered solar? You might be able to rig something together out of two solar yard lights. One panel can be set as normal, except you'll have to cut the LED out, and then run it into the lamp, and then reconnect it via wires. The second solar panel would be set up with the photovoltaic sensor covered, so it could run during the day. You'll have one panel that will charge during the day and run during the night, and the other can run straight off the sun. You can monkey with a setup like this and augment it with batteries if need be. If you are electronically inclined, you should be able to figure something out, or if you have a friend that is they should be able to figure this out in short order. (If you need to augment with batteries, a couple of pairs of good nimh batteries should be all you need. Those are 2400 mah or so, and the rechargable batteries that run an LED solar light all night are 600.)
posted by azpenguin at 10:32 PM on April 25 [1 favorite]

Can you modify the lamp such that it runs on DC power? Automotive, motorcycle and boating stores are full of 12v DC bulbs that are similarly sized to a nightlight bulb (though, probably not similar enough to just screw in... you'll need to wire in a bayonet socket.)

If you can put your hands on something near a 7 watt bulb that runs on 12v DC (that would be in the neighborhood of 0.6A - look for it stamped on the metal, just below the glass), a socket for it, and a gel-cell (or Sealed Lead Acid) 12v battery, you're in business. A fully charged 26Ah gel cell will run 7 watts for about 36 hours. If you're good about turning off the lamp during the daytime, that should be plenty.

FWIW, you can find the bulbs, and probably the socket at your local auto parts store and/or junkyard, and if you have the room, most car batteries would provide enough juice as the SLA above. If your forces of obtianium are strong...
posted by toxic at 11:59 PM on April 25

Feh.

...would provide as much juice as the SLA (Sealed Lead Acid)...
posted by toxic at 12:03 AM on April 26

Get a Sun Jar (I have one, love it) and either use it as-is, or take the light out to use in the salt lamp. The LED light unit is a sort of plastic cylinder topped with round solar panel. There's an orange LED light in the cylinder part. You could charge the panel during the day in bright sunlight and it will glow for about 5-6 hours. You could also use the innards of a solar garden light (like so), but in my experience they're not quite as bright as the sun jar. The nice thing about the Sun Jar is that it has an on/off switch, which solar garden lights do not have. Or just take the easy route and use one of those LED tea lights as recommended above: you'd probably need several since I think they only last a couple of hours, and I'm not sure if they'd be bright enough for your needs but they're easily found in any craft store so it wouldn't hurt to try.
posted by cuddles.mcsnuggy at 6:52 AM on April 26

BTW: Forgot to mention, I have a couple of those salt lamps (both the kind that's like a single block of salt with a hole in the bottom for the bulb, and the kind that's a bowl of rocksalt chunks with a bulb buried underneath them) so I know of which you speak, and it's easy to replace their light source with something else (like the LED/solar thing), so you don't need to think in terms of powering it with the electrical cord it came with.
posted by cuddles.mcsnuggy at 6:59 AM on April 26

I should clarify (and I am a dunce for not doing so originally, my apologies) that I actually tried an LED bulb in place of the incandescent one, and it's no where NEAR as bright. It makes some light, but not enough to either light the room at night, or look like a nice prop (Geek Filter: I'm using the bowl with chunks to be a "forge" for a blacksmith in the game, so it should be hopefully bright.) The LED bulbs work great as normal nightlight replacement bulbs, but not enough to light the inside of the salt lamp. I may need a brighter LED bulb...

I'm not a skilled electrician, but I might be able to find someone who is, and get the rig re-made. That is a good idea.

The Sun Jars do look cool, and I've seen them in use at the game. The main reason we're looking to use the Salt Lamps is for their appearance of a glowing rock, or hot coals, which makes good sense for the Role-Play setting at the game.

I'll see if I can post pics when I can line up some of the gear in a powered setting, so it makes more sense.
posted by GJSchaller at 7:33 AM on April 26

FishBike, that is an EXCELLENT idea. On top of powering the lamp, it helps in case someone's car dies in the middle of the campsite... and it CAN be recharged at one of the cabins with power, if mine does not. (A generator would not work, though, since the noise would ruin the atmosphere of the game.)
posted by GJSchaller at 7:44 AM on April 26

Just thought of another thing: Glow sticks! When you first set them off, they're very bright for a couple of hours then gradually get dimmer, but stay lit for about 4-6 hours total. You'd need to have a supply of them on hand, but you could try burying several under the salt rocks (depending how big your lamp is) and keep replenishing them with fresh ones as they get dim; they may even be brighter than LEDs. Dunno about NY, but here in WI you can buy these in party-supply stores, craft stores, and sometimes find them in the camping equipment area of stores like Target, Walmart, sporting goods shops.
posted by cuddles.mcsnuggy at 7:50 AM on April 26

After looking about online, I think I am going to go with a DieHard Portable Power 1150 Jump-Starter/AC-DC Power Source - This will not only give the lamp the power it needs, and the brightness I am looking for (consistently), but it has a double-function of being an air pump and a car battery jumper, which is handy. It even has a USB port for charging cell phones!
posted by GJSchaller at 5:10 PM on April 26