Using portable power for a fluorescent light

Discussion in 'Lighting Equipment' started by jstarks, Jun 13, 2009.

  1. Greetings gurus,
    I'm setting a up video shoot using a 220watt fluorescent fixture and the shoot are has no AC power nearby. My idea is to use a 600watt (continuous; 1000watt peak) inverter and a rechargeable 12volt battery. How many amps per hour (ah) should the battery be rated for? Should I explore this option or choose another area for the shoot? I found a thread that addressed using generators, but not batteries and inverters.
    Any assistance/advice you can provide would be helpful,
  2. 220 watts / 12volts = 18.3 Amps ...
    so from a 12 volt battery, the inverter will take something like 20 to 22 amperes continuously.
    One hour of light will therefore eat about 20-22Ah from your battery.
    Since usually a battery does not have its nominal charge, the battery should have more Ahs than you need.
    Example ... you want the light for 2 hours ... which gives about 44Ah .... the smallest battery I would try is a 60Ah. (This is a big car battery).
    The other problem can be the ignition of fluorescent lights ... in the moment before the tube is ignited, it has a quite high current consumption (except when there is an electronic starter), so you should not ignite all your tubes at the same time. Ignite them one by one.
  3. Thanks Rainer,
    I considered the initial start up for fluorescent lamps and I'd certainly power this light up slowly! :) Though I'm in Europe the fixture runs on 110/120 volts (120w/12v=10 amps) so I'll follow your suggestion of starting with a 20-22ah battery or higher for more shooting time. Do you think the inverter is sufficient to handle the potential load?
    Thanks again,
  4. -- "Though I'm in Europe the fixture runs on 110/120 volts (120w/12v=10 amps)"
    No, this is wrong. (you're confusing volts with watts).
    If your tubes need 200watts (as you wrote), they will need about 20Amps at 12volts.
    But you would need a 12v to 110volt converter, if the tube runs on 110volts (rather than a 12v to 220v converter). But this doesn't change the input current of the converter ... since for this side the calculation is 12v x 20Amps = 240Watts.
    A converter that is capable of producing 600watts contiuously (and 1Kw peak) should be more than enough for this setup.
  5. Another thing to worry about is the type of ballasts in the fixtures. There are three different kinds of ballasts commonly available: magnetic, low-frequency electronic, and high-frequency electronic. Make sure you have high frequency electronic ballasts in your fixtures. These tend to be the most stable when running from ill mannered power sources such as square wave inverters or generators.
    • Magnetic fluorescent light ballasts are inductive devices, and are insanely sensitive to the waveform powering them. They often do interesting things when run on square wave (typical low cost 600W) inverters, such as not starting, flickering, or running at too low or too high a current. Fluorescent lights are surprisingly sensitive to their drive current: too high or too low current will cause fluorescent light to drift in both color temperature and CRI (color rendition index).
    • Low-frequency electronic ballasts are just as bad. Their current output varies substantially with the waveform, and they overdrive lights unpredictably when driven from square wave inverters.
    Of course, a pure sine wave inverter will drive any kind of light ballast properly, but they're much more expensive and much heavier than square wave inverters of the same power rating. My 300 W sine wave inverter cost about $400. And it's bigger than the typical 600 W square wave inverter.
  6. Thanks Rainer I'll still look into getting at least a 20-22ah battery. Now the fun part is researching my options!
    Joseph thanks for the advice on ballasts and the inverter I'm eyeing is a pure sine wave device and you're right they are expensive.
    Thanks to you both,
  7. Can't you rent a generator?
  8. I'm sure I could rent a generator, but I'd prefer going with something a little more portable.

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