how much power does this light need?

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LowePro
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how much power does this light need?

Post by LowePro » Wed Mar 12, 2014 4:29 pm

Hi, a question for electrical experts:
I scored a strobe light at a garage sale. It plugs into a normal wall outlet. The sticker on the back says:

115 volt, 60 hz
max 2 watts - 310 mA
Xenon

On the playa, I run a 12V deep cycle battery with an inverter and a power strip. My question, is this strobe light going to be a significant draw on my battery?

I know how to convert watts/amps/amphours etc for my 12v gear, but this AC plug strobe light throws me for a loop. Thanks all.

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Molotov
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Re: how much power does this light need?

Post by Molotov » Wed Mar 12, 2014 4:51 pm

2 watts @ 115 volts isn't very significant. I imagine the internal current demand for your inverter will far exceed anything needed by the strobelight itself. I would putt an amp meter on your inverter running without any devices connected to it to see what it consumes on it's own. Inverters are most efficient when operated near capacity and this strobe just won't stress it very much.
Last edited by Molotov on Wed Mar 12, 2014 4:53 pm, edited 1 time in total.

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Joeln
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Re: how much power does this light need?

Post by Joeln » Wed Mar 12, 2014 4:52 pm

figure some efficiency losses when you use the inverter.
Thing is rated at 2 W probably by the time you invert your 12 volts it will cost you maybe 3 W.
That's a fairly light load
Then again, how efficient of an inverter you have and your battery capacity and other loads will all come into play.

What other loads are you familiar with running off the inverter?
Take the wattage of them and your experience running them then do the math.

If the strobe is the only thing you run off the battery you could get 15 to 30 hours of runtime depending on the spec's of your battery/inverter.
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Re: how much power does this light need?

Post by EspressoDude » Wed Mar 12, 2014 5:03 pm

12v vs 120 v ~= 1/10 of the voltage means approx. 10 x the current. 310mA x 10 = 3100mA or 3.1 amps
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Re: how much power does this light need?

Post by FossaFerox » Wed Mar 12, 2014 6:15 pm

Am I missing something? The stated voltage/wattage/amperage don't line up. 310mA at 115V should be about 35 W, not 2...
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Re: how much power does this light need?

Post by BBadger » Wed Mar 12, 2014 6:40 pm

FossaFerox: Remember that power = energy / time. The 2W figure is small because he's operating a strobe light which have very short duty cycles.

asr9754: To find out how long your batteries will last: Voltage * Amp-hours of your battery / power consumption.

Ex: 12V battery with 60AH capacity = 2 592 000 joules
2 592 000 joules / 2W = 15 days

You probably don't want to discharge below 50% though, so divide that figure by half.
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Re: how much power does this light need?

Post by nixiebunny » Thu Mar 13, 2014 10:42 pm

Your best bet to learn how much power it needs is to run it at home for an hour, and measure your battery's voltage before and after. You can calibrate your test by running a 7 watt incandescent bulb for an hour and measuring voltage before and after. Then the math becomes easy.
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TheMongoose
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Re: how much power does this light need?

Post by TheMongoose » Sat May 10, 2014 12:29 pm

OK,

I'm a PhD electrical engineer, I can help with this. You have a 12V Battery, How many Amp-Hours is it? The capacity is the important thing here.
Like the previous person stated the strobe is rated for 240 V.

Power = Voltage x Current.

So if you have 10 times less Voltage you need 10 times more current, to get the same amount of power. Also as you will be running it off an inverter you will loose around 5% of your energy in the inverter.
The power is the only thing we need to consider here. The Amp-hours of the battery will allow me to calculate this for you.

:)

Chris

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Token
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Re: how much power does this light need?

Post by Token » Sun May 11, 2014 2:52 pm

Normally 2W is just 2W. The strobe gizmo is 2W. Think of it as one of those fancy new headlamps in terms of power. A handful of AA batteries will run it all week, right.

The crappy part of that particular 2W is that a strobe is off most of the time but when it is on it is drawing 35W for a very short time. This is why the current is listed, cuz the duty cycle is so low.

So your inverter will get a hell of a workout running 3-4 A bursts at the strobe frequency. Usually best effect is 8 - 12 Hz.

A strobe light is one of the worst things you can plug into an inverter, right up there with a stick welder.

Run it for a few hours at home to see if your inverter heats up or fries, for sure. Not worth getting all surprised on the Playa.

P. S. Edited to correct autocorrect.

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Re: how much power does this light need?

Post by GreyCoyote » Sun May 11, 2014 3:05 pm

Stick a Kill-A-Watt ($35) between the cord and the wall. See what peak and average loads are like. You should also be aware the power factor on these is usually REALLY bad (hugely leading or lagging, depending if they are using a capacitor-based tripler or an inductor-based pump). Just putting some power factor correction into these helps a bunch if running from an inverter. Inverters really do not like reactive loads.

The best way is to just measure it. Anything else is pretty much benchracing. :mrgreen:
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EspressoDude
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Re: how much power does this light need?

Post by EspressoDude » Sun May 11, 2014 4:06 pm

ACR ELECTRONICS

C-Light Personal Light #3355 $12.00
8hours with two AA batteries

Automatic Floating Strobe Light #3940.1 $129.00 visibility 3miles
60hours with 5volt lantern battery

strobes don't need much power
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Re: how much power does this light need?

Post by daft » Thu May 29, 2014 6:16 pm

I wish I would have paid more attention to electricity in school

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