High power u/w video light

[MantaRey]

I've been wanting to do this for quite some time. I can solder and make water tight containers etc. But, since I am far from being an electrical engineer I have one technical misunderstanding:

How is it possible to power a 200w HMI by battery?

Wouldn't the power being pulled from the light drain something like a 12v battery in an instant? I'm thinking in terms of something like a car stereo; one thump from a 200w subwoofer and the alternator is already charging the battery. So, how are these kinds of lights wired so that you can get at least some usable time on one battery charge (say at least 30 minutes).

Something like this: http://www.pacetech.com/Lights/HMI_s/200_W_SEB/200_w_seb.html

Only far more affordable.

 

[ronrosa]

I've read something about dividing the wattage by the voltage to get the required amperage. So 200 watt light divided by 12 volts equals 16.6 amps. Might want to look into a 12 volt 18 amp battery.

 

[SmileMon]

If I'm not wrong, HMI is like HID, Xenon (real xenon) and Sodium lights.

They work by igniting a liquid/gas inside the bulb, their rating/consumption is a bit different as they can't be used in low voltage and require staging electronics to get to higher voltage of 70-600 volts - with battery.
If you use 110v/220v it usually uses that voltage plus a coil that gives it momentary high voltage for ignition - much like fluorescent.

The battery conversion electronics is usually very efficient - however, a lot of energy is lost mostly to heat.

I've found this while looking for lights..
http://www.hydroflex.com/site/lighting/lighting.html

I wonder how good it is for night/cave diving... 1200w sounds like a nice thing to have in a cave "ok everyone, turn off your lights, we can't see them anyway..."

 

[MantaRey]

They have up to 6000w which is just ridiculous. lol. And yeah HMI simply signifies the kind of bulb which uses a different element in the gas to provide a different kind of light. The good thing about HMI bulbs is that with their frequency they are more efficient when it comes to light quality (ie a 200w HMI equals a 600w regular bulb).

But of course the issues lie in powering it, and the fact they they get fire hot. I'll look into the amp thing ron, I've heard you have to also take into considerationg the mah of the battery. But I'm wondering if there's some kinda of transformer involved.

Of course I could just have a really long extension cord running up to a generator on the boat.

 

[Kwbyron]

From what I understand, from my father, physics in high school, and reading on line:
Watt = Amps * voltage. If you look on a battery it will give you mAH (milliamp-hours) which means that the battery can deliver that many amps for 1 hour before becoming dead. So like, my project is a 12v 50w halogen, I bought 10 1.2v 5000mAH c-cell batteries. Using the equation above, you can rearrange it and solve for the amps the light takes, A = W/V ; 50/12 = 4.167 amps. So this is the amount of power the light will draw. If I want a 1 hour light, I need at least this many amp hours. I'll get 1.2 hours with my c-cells.
Higher voltage will increase the intensity of the light, but like I was pointed out, will also burn the bulb quicker...but since they are inversely proportional it will also reduce the amount of amps drawn. So if you have a 200w bulb running on 12 volts, you will need batteries to put out 33.33 amp-hours of power to get an hour burn time. You can wire batteries in parallel to increase the amount of amps and series to increase voltage.

 

[mbsub]

Hello,
maybe you get some idea, if you look the attached folder of our Foto-Light and our Video-Light.

Michael

sorry, i see only now, thats an old thread

 

[cjfox]

I made a low budget 200w halogen video set up with 2 100w bulbs in glass heads, and a 12v 12 ah lead gel cell, out of PVC sewer pipe. Works great, I get about 35 min burn time, and I just swap out batteries on the surface interval. It's big (my dive buddy calls it the volkswagon) but it's cheap, and I'm happy with the lighting in the finished footage.