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Stupid Electrical Question

Old 10-22-04, 12:56 PM
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Stupid Electrical Question

Calling on the power of the Otters...

Is there a device that can turn a AC plug-based device into battery powered?

That is, if I have an item (say, a lamp) that uses a standard 3-prong plug... but I want to use it somewhere where there is no electrical outlet... is there any piece of battery-powered hardware out there to plug it into?

Just a strange situation that came up in conversation today.
Old 10-22-04, 12:57 PM
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You can use a power inverter along with a battery. However the battery will need frequent recharging.
Old 10-22-04, 01:01 PM
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Yeah, it's called an inverter. You get one for whatever battery source you want and ensure that the output is enough to power the AC device (110VAC output). A lot of these are built for car installations, so they expect a car battery type of input (12VDC).
Old 10-22-04, 01:02 PM
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like X said, a power inverter (or perverter) can let you use it off of DC...like a car battery.


a generator would work too.
Old 10-22-04, 01:11 PM
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Ah, I see... thanks.

But there isn't any cheap way to set this up for something trivial like a lamp? A generator or car battery is probably overkill. They don't make a device that uses a standard battery (9-volt, D, whatever) that could do that task? Even if it required frequent recharges?

I've just done a Google search and it seems that every inverter is designed for car use.
Old 10-22-04, 01:12 PM
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Get a battery powered lamp instead of an AC powered lamp?
Old 10-22-04, 01:13 PM
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Re: Stupid Electrical Question

Originally posted by bboisvert
That is, if I have an item (say, a lamp) that uses a standard 3-prong plug... but I want to use it somewhere where there is no electrical outlet...

If somewhere happens to be in your house, then it is way more practical to install a new outlet. Even if it is difficult to do so.
Old 10-22-04, 01:15 PM
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Originally posted by bboisvert
I've just done a Google search and it seems that every inverter is designed for car use.
You just cut the lighter plug off and put on a couple clamps that attach to a car battery. I use them to keep the fish tank running when the power goes out.

A lamp isn't trivial considering the amount of wattage you need to run it.
Old 10-22-04, 01:16 PM
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Cool, I guess that answers my question... thanks.
Old 10-22-04, 01:17 PM
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use a flashlight?!?
Old 10-22-04, 01:29 PM
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A normal 9 volt battery has about 500 mAh in it.
P=VI, which means I=P/V. A 100 Watt bulb, from a 9 Volt (assuming a perfect inverter), would draw about 11 amps off the battery.

0.500 / 11 = 0.0454 hours, or 2.7 minutes of actual operating time. This assumes the batteries cells don't overheat and burst because of the power drain you're putting on it, which is a pretty large assumption to make given the drain and the battery.

9 Volt batteries don't have the power in them to power a simple 100W household lightbulb. They just don't. No magic equipment will change that.

Even if you use one of those biggish 6 Volt flashlight batteries, you're looking at around 2500 mAh. 100/6 = 16.666 Amps. 2.5 / 16.66 = 0.15 hours = 9 minutes of operating time.

Last edited by Otto; 10-22-04 at 01:32 PM.
Old 10-22-04, 01:31 PM
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Candles man.....candles.....
Old 10-22-04, 01:39 PM
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Thanks for the figures, Otto. Again, it was really more of a theoretical question that came up. Looks like it isn't possible. I figured it probably wasn't... since I had never heard of such a device.
Old 10-22-04, 01:59 PM
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Right. For that sort of thing, you generally want to use a car inverter along with some form of "deep cycle" battery, like a golf cart battery or a marine battery or something. Finding these with capacities of 100Ah is not out of the question. With a 100Ah 12VDC battery and a 100W bulb, you could get 12 whole hours out of it, in a theoretically perfect system. But you really need that "deep cycle" battery, because a normal car battery is designed more with Cranking Amps in mind, and will discharge very quickly on a constant small load like that. Also would probably damage the battery with long term usage. Deep Cycle batteries have much thicker plates to account for this sort of usage.
Old 10-22-04, 02:07 PM
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Originally posted by Otto
A normal 9 volt battery has about 500 mAh in it.
P=VI, which means I=P/V. A 100 Watt bulb, from a 9 Volt (assuming a perfect inverter), would draw about 11 amps off the battery.
Well, *obviously*...
Old 10-22-04, 02:35 PM
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what about the big 9 volt batteries, like the ones you find in... um... those blinking orange roadside construsction lights
Old 10-22-04, 03:01 PM
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Originally posted by RoQuEr
what about the big 9 volt batteries, like the ones you find in... um... those blinking orange roadside construsction lights
First you'd have to find an inverter that worked with 9 volts and then you'd have a power source that wouldn't last anywhere near as long as a car battery.
Old 10-22-04, 03:10 PM
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How about the opposite, converting a battery-powered device to a plug-in device?
Old 10-22-04, 03:13 PM
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Originally posted by leepyswetr
How about the opposite, converting a battery-powered device to a plug-in device?
jam a couple of paper clips into the outlet and run a wire from them to whatever you want to power
Old 10-22-04, 03:16 PM
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Originally posted by leepyswetr
How about the opposite, converting a battery-powered device to a plug-in device?
That's called a transformer or power adapter or battery eliminator.
Old 10-22-04, 03:24 PM
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Go to any store and pickup a little universal transformer. It's got a switch on it and several types of plugs on the other end (including a 9V battery type connector). Dial in the voltage and polarity, plug it in, and off you go. Or just use rechargables.
Old 10-22-04, 04:20 PM
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Originally posted by Otto
Or just use rechargables.
My senior design project from several years ago was a concrete coffee table with fiber optic strands embedded in the top. The light source is battery powered. As the TA failed to provide us with our requested lightweight aggregate, the top weighs about 80 lbs, making it impractical to lift up and turn on the light each time I want it to look cool. Thus the need to convert to a cable. Would a typical adapter have a AA-type connector as well?
Old 10-22-04, 04:41 PM
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If it's outside, try solar cells.
Old 10-22-04, 05:14 PM
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Portable AC/DC power source + it will inflate tires and jump start your car if needed all in one device $120

http://www.stayonline.com/temporary_power/1683.asp

Little bigger $149 (even states some AC operation times)

http://www.stayonline.com/temporary_power/1666.asp

I just did a quick google on this, I am sure you can find them cheaper elsewhere
Old 10-22-04, 06:16 PM
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The banner for this is now from all-battery.com

My thread now has official sponsorship. Excellent.

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