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How do I convert an AC device to run on a battery pack? Answered

I have a device that runs on ac (110-120 Vac - 180w). I want to make it portable so that it can run off a battery pack such as AA or 9 Volt or even a custom battery. Is this too much of a power requirement to make it possible??? thanks in advance for your help.



7 years ago

Is there a way to take a string of Christmas lights, which plug in, and convert that to something that can be strung on a vehicle or a person using AA batteries? how would I go about doing that?

Not easily, if you're talking about "classic" incandescent bulbs. Those strings don't have a transformer; they use 110VAC directly from the wall.

If you are using LED light strings, you might be able to do it, depending on what kind of LEDs they are. If the light string has a transformer and rectifier built it (like a wall wart, but small) then you could cut that off and hook the bare leads to a battery holder. Make sure you get the ends oriented correctly (the whole point with diodes is that they only allow current in one direction). You'll need to know the voltage required by the LEDs in order to do this.

I'm pretty ignorant about the whole thing. I'm talking about the regular strings that you would buy like at family dollar or anywhere?

Hmmm....do the bulbs you have unscrew from the string? If so, they're incandescents, and you can't run an incandescent string off AAs -- you could use (several) lantern batteries, or connect a car cigarette-lighter plug to the wires.

If the bulbs are permanently attached to the wires, where you can't remove them at all, then they are LEDs.

They are regular little bulbs with the rectangler plug end with the 2 tiny wires. Little cheap regular Christmas tree lights.

Okay. Unfortunately those pobably aren't LEDs, they are incandescent. You'd need to use large, hefty batteries (like the square lantern batteries) to get any decent light out of them.

Yeah but as goodhart says a deepcycle marine battery would do well but so does a 12V truck battery, they're usually in series for the 24v systems found on trucks, these are similar to heavy duty car batteries but have massive cranking current and larger capacities (not a huge difference in capacity). They withstand higher current draw from larger inverters much better than other batteries, granted they're harder to find now that most trucks are being fitted with single 24v batteries. Though you coulld run two twelve volt inverters in parallel and 12v each.

Wouldn't an even deeper cycle marine battery work better ?

Yes, its just that it doesn't have the plug for the inverter (but thats pretty easy to hook up by yourself)

Oh, I just meant that it would have more umph then a normal automobile battery.

A 180W device would be drawing 20 amps out of a 9V battery. There is no way the terminals could withstand that much power. 8 AAs wired in series would produce 12V, which would still require a 15A draw. Again, that would cook your batteries. 180W is a lot of power.

If by "portable" you mean "handheld," not a chance, unless you spend a few hundred and get a custom Li-ion pack made. If by "portable" you mean "doesn't have to be plugged in," your best bet would be a [http://www.allelectronics.com/cgi-bin/category/160400/Gel_Cell_(Sealed_Lead_Acid).html 12V sealed lead-acid battery,] with as high of an AH capacity as you can carry/afford.

As Kiteman said, it would be easier to help if we knew what you wanted to do.

Oh, and that's 8 non-rechargeable AAs, e.g., alkaline, carbon-zinc, zinc-air. Most rechargeable AAs (Ni-Cd, Ni-MH) have 1.2V cells, so you would need 10 to produce 12V.

You are not getting 180 w out of a an AA nor a 9 v battery, for sure.

What's the actual device, it'd help alot to know, as kiteman said many are actually designed to run on DC with a transformer.

A lot of devices built to run off AC are actually DC, with a built-in transformer (to change the voltage to whatever the device needs) and rectifier (to make the current DC).

Check the innards of your device - if it contains such a transformer / rectifier, then you should be able to replace that with a battery pack that gives a similar output. It may even fit in the space made by the removal of the transformer / rectifier.

Further to that, if you only need the device for short bursts, think about using supercapacitors as your power pack - they did this to a cordless screwdriver in Popular Mechanics, and 90s charging gave enough oomph to drive in a couple of decent screws.

Of course, if you told us what "the device" actually is, others would be able to give more detailed help)