Battery Power For Lights Outside With No DC Power Around

[Robertofish]

I want to use lights outside, for this it will be the Lowel Tota Light and the Pro Light also by Lowel, however in the locations that we will be filming there are no plug in areas as it is outside, is there any way to do this like an external battery that you can plug into or something?

 

[j1clark@ucsd.edu]

I want to use lights outside, for this it will be the Lowel Tota Light and the Pro Light also by Lowel, however in the locations that we will be filming there are no plug in areas as it is outside, is there any way to do this like an external battery that you can plug into or something?

There are a number of 12V car batter setups that can be used to feed an inverter to generate the 120V power you'd need. There's a couple of threads on the topic of inverters and use with film lights. If I have time later, I'll see if I can search for them.

But one needs to calculate how much power one needs for now long, and figure out what amount of 'battery power' you will need.

For example:

Lowell 500 W lamps, from basic Ohms law calculations yield 5 amps (rounded) at 120V. Say 7 amps, due to inefficiencies in the inverter, and your shoot is 4 hours.

You'd need 30 amp-hours worth of battery... but there are a number of factors that often do not allow you to get 30 amp-hours, so, you'd go for something that has 100 amp-hours, that can deliver a continuous 7 amps... and have a back up set...

On the other hand, there are generators that have been mentioned in various threads as well...

 

[Robertofish]

cool its good to know that there are options out there for external battery power, where would I get these things mentioned or what would I search on google?

 

[maplecap]

It is, of course, common to shoot outside with lights. It is, however, uncommon to power tungsten lights off of batteries (excluding small cam lights, etc.). Typically one runs power distribution (stingers) from nearby AC outlets or utilizes a generator. The little Honda EU2000i is popular for small shoots, widely available for rent, quiet and as foolproof as gennys get.

If you really want/need to use battery power, consider small HMI's (200w) and battery belts or blocks. You can find info on power requirements and runtime of popular models online.

 

[David W. Jones]

As mentioned, battery power to sustain tungsten lights would be very expensive. Renting a quiet generator is an option.
I have a set of LED lights which do well as battery powered since the power draw is much less than tungsten lights.

 

[Norman99]

Is the shooting during the day or at night, as you will need more light for a daylight setup ( fill shadows/ backlighted scenes/ directional fill etc.) ? Daytime, go with the portable generator as you will most likely need much more light units especially at further distances. At night, a battery option may do, again depending on distances and estimated shooting time would roughly determine the battery(s) run time. As shootings go, I would estimate much more time than anticipated for retakes, setups, focusing before the actual takes etc. Try out your lights where the AC is available with the approximate light levels anticipated, this will tell you if your lights will be bright enough. If you go with batteries (car types) and inverters, make sure you run each light with a separate battery and inverter as too much power draw from a single inverter will most likely trip the protection circuit. Be careful with the wiring especially at wet areas. Good luck.

 

[Norman99]

http://www.adaptelec.com/dc-to-ac-inverters-12v-to-110v-c-9.html

 

[Robertofish]

Day or night I'm planning to buy something that works for both, the honda generator how does it work exactly, I don't know that much about generators does it create power, through gas? and is it very wasteful, and how long would it power lights for or does it just depend on how much gas you have? I was also looking into NP1s but they don't seem like they would last very long, and this is the same price.

 

[Norman99]

Generator? You put gas, motor spins, makes some noise ( the further away the better), spinning motor connected to an alternator to produce electricity. Exact working details are available somewhere on the web. Wasteful ? not much more than a small motorcycle. The more gas you have, the longer it runs. What are the NP1's you mentioned ???

 

[j1clark@ucsd.edu]

Day or night I'm planning to buy something that works for both, the honda generator how does it work exactly, I don't know that much about generators does it create power, through gas? and is it very wasteful, and how long would it power lights for or does it just depend on how much gas you have? I was also looking into NP1s but they don't seem like they would last very long, and this is the same price.

Generators produce electricity by essentially the same principles as the power grid is powered, a magnet spins, a coil of wire with a magnetic field spins, or whatever, and induces an electric current in the wires that bring the power to the device.

I'm sure there are plenty of wikis on this sort of thing. The biggest problem with generators is noise. Depending on the generator, one will hear the gasoline engine running (big huge rigs are powered by diesel engines...). The Honda series is noted for being quite, but as others point out... quiet is a 'relative thing', and even the Honda may produce too much noise for sound recording during the shoot.

But the generators do produce far more power more cheaply than batteries.

If your shoot can 'stand' a generator, that would be the recommended method for locations that have no power otherwise. If for some reason a generator can't be used, batteries are it... I did sort of interpret you're question in that direction...

 

[nejuicer]

http://www.dvxuser.com/V6/showthrea...With-No-DC-Power-Around&p=2367338#post2367338

The biggest problem with generators is noise. Depending on the generator, one will hear the gasoline engine running … The Honda series is noted for being quite, but as others point out... quiet is a 'relative thing', and even the Honda may produce too much noise for sound recording during the shoot.

It depends on what generator you use and how you use it. The problem with portable generators even the super quiet Hondas, is that by the time you move them far enough off set that you don’t hear them you have significant voltage drop from the long cable run back to set. To the problem of line loss, you have the added problem that as you add load the voltage drops on portable generators. It is not uncommon for a generator to drop 5-10 volts under full load. The combination of voltage-drop on the generator, and line loss on a long cable run, can cause voltage to drop to the point where HMI and Kino ballasts won’t strike. The effect of line loss on tungsten lights like those x proposes to use can also be dramatic because their output falls off geometrically as the voltage decreases. For example a 1k lamp operating at 90% rated voltage (108V) produces about 68% of its normal light output - your 1kw lamp is now a 650W lamp.

But, that is not all, as the light intensity decreases, so does the Kelvin color temperature of the emitted light. In the case of fluorescents, HMIs, and LEDs, because their power supplies are typically of a “constant power” type, they will draw more current as the line voltage decreases in order to maintain constant power to the lamp. In the case of generator output, voltage loss translates into an exponential loss in power. That is because, if you double the ampere load on the cable, the voltage drop also doubles, but the power loss increases fourfold. What this means is that when a distribution system has a large voltage drop, the performance of the generator (its maximum effective load) is reduced. For these reasons it is worthwhile understanding the dynamics of line loss and how to mitigate it.

A Distro System consisting of a 60A Full Power Transformer/Distro, 2-60A GPC (Bates) Splitters, 2-60A Woodhead Box distributes power from a modified Honda EU6500is. Even though the generator is 100' away to reduce noise, plug-in points remain conveniently close to set.​

The trick to using HMIs & Kinos on portable generators is to use a generator, like the Honda EU6500is, with a 240V-to-120V step down transformer that has a slight voltage boost built into it. The Honda EU6500is inverter generator to begin with is much quieter than the other portable generators and even Honda’s older movie blimped Honda EX5500. Part of what makes the new Honda EU6500is so quiet is it's "Eco-Throttle." The Eco-Throttle's microprocessor automatically adjusts the generator's engine speed to produce only the power needed for the applied load. It can do this because the inverter technology of the Honda EU6500is enables it to run at different RPMs and maintain a constant frequency and voltage. Where conventional generators like the Honda EX5500 and ES6500 have to run full speed at a constant 3600 RPM to produce stable 60 hertz (cycle) electricity, a Honda EU6500is only needs to run as fast as required to meet the load demand. Since their engines do not have to run at full speed, and given the fact that an inverter generator generates 20% more power per revolution of the engine, makes the Honda EU series of inverter generators substantially quieter than conventional models.

The net result is that the EU6500is operates between 34 to 44 dBA at 50 ft. - half as loud (ten decibels) as the comparable EM7000is and ES6500 generators and comparable to full size movie blimped generators like the Crawfords. But you can't park a Crawford right on set and record sound without picking up the generator either. With sound specs this good all you need to record sound with a Honda EU6500is without picking up generator noise is a real distro system that will allow you to move the EU6500is off set (like you would a Crawford), minimize line loss over a long cable run, and provide plug-in pockets conveniently close to set. That is where the transformer comes in.

To record sync sound without picking up any generator noise, all you need to do is add 300' of heavy duty 250V twist-lock extension cable between the generator and a transformer/distro. This is usually enough cable to place the generator around the corner of a building, or to run it out of a van or truck - which is usually all the additional blimping you need with these generators. The heavy-duty 250V twist-lock cable eliminates multiple long cable runs to the generator and minimizes line-loss; as well as, eliminates the sever voltage drop you would have using standard electrical cords (see example below for details.)

Boost Transformers allow you to adjust for line-loss with a selector switch to maintain 120V on set.​

To assure full line level (120V) on set, use a transformer/distro designed to compensate for the inevitable slight line loss you will have even over an extended run of 250V twist-lock cable. That is, use one designed to slightly boost the voltage on the load side (secondary). With these "boost transformers," if you were to feed the supply side (primary) of the transformer 240 volts from the generator, 127 volts would come out on the secondary side where you plug in the lights. This slight boost enables you to place the generator further from set where you won't hear it, yet assure that the supply voltage on set does not drop too low.

A good example of how a transformer/distro makes it possible to record clean audio tracks even under the worst of conditions is the indie short "Toothbrush." In this story of mistaken identity produced by Guymanly Productions, a pivotal scene takes place in the middle of a near vacant parking lot of an all night convenience store. With no building or other sound barrier within a reasonable distance to block the sound of the generator, Gaffer Aaron MacLaughlin had no recourse but to put it behind their grip truck as far from set as possible.

Left: Scene in parking lot. Center: Transformer/Distro hidden behind newspaper box (set 200' in distance.) Right: Generator baffled by truck (Transformer/Distro 300' in distance.) ​

As you can see from the photos above, he ran 300' of twist-lock extension cable from the generator to our 60A Full Power Transformer/Distro hidden behind a newspaper box. From the Transformer/Distro he then ran 200' of 6/3 Bates Extension to set where he broke out to 20A Edison receptacles using a 60A snack box. While running the generator near full capacity with a lighting package that consisted of three 1200W HMI Pars and two 1k Baby Quartz Fresnels, he experienced no appreciable voltage drop on set even after a 500' cable run because our Select Transformer/Distro was able to compensate for both the line loss of the cable and voltage drop of the generator under near full load.

This example shows how the variable boost of a transformer, not only enables you to place the generator further from set where you won't hear it, but also assures that the supply voltage on the secondary side of the transformer does not drop too low. By comparison, had Aaron run 500' of standard 14 Awg electrical cord he would have experienced a line loss alone of 24.5V (according to the line loss table above.) With that severe a voltage drop, his HMI ballasts would probably have cut out from low voltage as he added additional loads on the generator. Without the line-loss compensation of our Transformer/Distros, he would have had to move the generator closer to set where it would be picked up on the audio tracks.

For more detailed information on using transformers on set, I would suggest you read an article I wrote on the use of portable generators in motion picture production. Harry Box, author of “The Set Lighting Technician’s Handbook” has cited my article in the just released Fourth Edition of the handbook. In addition, he has established a link to it from the companion website for the Fourth Edition of the Handbook, called“Box Book Extras.”

If you haven't yet read the article, or looked at it in a while, it is worth reading. I have greatly expanded it to be the definitive resource on portable power generation for motion picture production. Of the article Harry Box states:

"Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."

The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

 

[slondon]

Line loss and voltage drop calculator is here: http://www.stealth316.com/2-wire-resistance.htm