Running Lights off a generator

[Zblock]

Hey guys. I have 3 650watt lights and I;m going to be shooting out in the desert running a generator. Is the math as simple as 3X650 = 1950watts so I'd need at least a 2kw genny to run my three lights?

Anybody have experience using these battery generators. They're silent which would be amazing for sound but I don't know how long they'd last. If you've used one before let's hear your story. Thanks,

Xantrex 1500 Watt Portable Electronic Generator

http://www.indierentals.com/?page=product&id=1170114

 

[David G. Smith]

Yeah, to my knowledge, the math is that simple. However, for those generators, I would look at the applications that it is rated for. It looks like that those gennys are for intermittent use for emergencies or campsite type of applications. It may be possible that running 3 650 lights off them would drain them in a very short time.

If I were in a situation where these gennys were the absolutely only option, I would go with some type of CFL lighting. If the use of 650 watt incandescence lights was the absolute, I would look for other power options.

 

[floop]

If my math is right...

3 650w tungstens would run off a 60amp/hour battery inverter for....

18 minutes!

You want a gas powered generator. I HIGHLY recommend the honda inverter generators like the 2000i. It is amazingly quiet for a genny. If i put it at the end of a 40 foot extension cord, it usually doesn't show up at all in the mic. They run all day on a few liters of gas and are light enough that you can carry one by yourself on a reasonable hike without dying. Just a magical machine.

 

[Paul Hudson]

David is right. It will run your lights but not for very long. You need a gas powered generator.

The Honda one he mentions is very quit but not silent.

 

[Zblock]

Thanks Guys. I'm gonna craigslist that Honda right now

 

[David G. Smith]

If my math is right...

3 650w tungstens would run off a 60amp/hour battery inverter for....

18 minutes!

You want a gas powered generator. I HIGHLY recommend the honda inverter generators like the 2000i. It is amazingly quiet for a genny. If i put it at the end of a 40 foot extension cord, it usually doesn't show up at all in the mic. They run all day on a few liters of gas and are light enough that you can carry one by yourself on a reasonable hike without dying. Just a magical machine.

How do you do that math? Is there a formula?

 

[4100xpb]

3 x 650 w lights = 1,950 watts

While the generator provides output power at 120 volts, its supply is a 12V battery.

1950 watts / 12 volts = 162.5 amps

The battery holds 60 amp-hours.

60 amp-hours / 162.5 amps = 0.37 hours, or roughly 20 minutes. This doesn't account for electrical losses due to wiring resistance or the inversion process, so actual time will be even less.

 

[Eileen Ryan]

I'm gonna craigslist that Honda right now

Don’t give up on the Xantrex 1500W Generator quite yet. You can extend it’s running time by making up a "jumper cable" to attach to the leads of a car alternator. That way you can use the car engine as a generator to run the lights during set up and rehearsals. When it comes time to shoot, shut off the engine and continue to run the lights on the silent Xantrex 1500W alone. Running the vehicle engine between takes charges the batteries so that they will last longer. I have used a similar rig to power lights all night for an independent feature shot in the Boston area by the name of “Shuttle.”

Exo-skeletal pipe rig on shuttle to rig lights and mount 750W batt-verter on front (covered for rain protection)

The production stills attached show you two similar Battverter rigs we used to run kinos inside and outside an airport shuttle bus for movie which takes place almost entirely on the bus.

750W "Batt-Verter" Rig wired into in Calzone case and tied into the Shuttle’s alternator

Like the Xantrex 1500W, a "Battverter" system consists of a deep cycle 12V DC power source (usually Marine Cells), a 12V DC-to– 120V AC True Sine Wave Power Inverter, and a Battery Charger. Use this link - http://www.screenlightandgrip.com/html/shuttlemailintro.html -
for details on how we wired it into the shuttle bus.

1800W "Batt-Verter" Rig wired into the back of Shuttle

The first is a 750W "Batt-Verter" rig wired into in Calzone case and mounted on a Exo-skeletal pipe rig that also held a couple of 4’ Kino Flos. The second is a 1800W "Batt-Verter" rig we used to run 16 - 4’ kinos tubes inside the airport shuttle. 1800W is the largest true sine wave inverter I have seen, which is still not enough to run your lights, so you should consider using two.

SL&G's custom 1800W BattVerter powers 16 - 4' Kino Flo single tubes rigged in the interior and on the exterior of an Airport Shuttle

If you need more than 1800Watts you have no alternative but to use a small portable generator.

- Eileen Ryan, Boston Gaffer

 

[nejuicer]

...Anybody have experience using these battery generators. They're silent which would be amazing for sound but I don't know how long they'd last. If you've used one before let's hear your story.

I second Eileen’s idea. I likewise have been able to run loads continuously on Battverters by jumping them onto car batteries and running the car during set up and rehearsals. When you do this you realize how little time is actually spent shooting takes. But, you have to be really careful when choosing a DC-to-AC inverter for film production because there are three basic types of inverters and not all of them are suitable for production applications. For instance, according to Xantrax’s website (http://www.xantrex.com/web/id/63/p/222/pt/10/product.asp) the Power Generator 1500 is a “Modified Sine Wave” inverter and therefore not good for HD cinema productions. “Modified Sine Wave”, “Psuedo Sine Wave”, and “Cycloconverter” are all sales terms used for a modified square wave type of AC power generated by inverters with limited switching capacity. Modified square wave (MSW) inverters are low in cost and will satisfactorily operate almost all common household appliances and power tools. For this reason, MSW inverters are the most prevalent and the ones typically used in the economy RV/Residential Standby and Industrial lines of inverter generators. Unfortunately, they are not suitable for use in motion picture production except for the powering of quartz lights. A modified square wave will cause sensitive electronic equipment (computers, hard drives, video cameras) to overheat, and will cause electronic HMI and Fluorescent light ballasts to kick harmonic noise back into the power stream. Furthermore, electrical components that depend on the peak value of the voltage waveform to operate effectively (the diode-capacitor power supplies in computers, hard drives, and electronic HMI ballasts, as well as the bridge rectifiers of battery chargers) will not operate effectively on a modified square wave. For a more detailed explanation of what makes an inverter suitable for motion picture production, see the following thread: http://www.dvxuser.com/V6/showthread.php?t=137712.

Guy Holt, Gaffer, ScreenLight & Grip , Boston[/QUOTE]

 

[nejuicer]

… You need a gas powered generator.
The Honda one he mentions is very quit but not silent.

Phudsontx is right that the Hondas are not silent. So it comes down to how you use them. In my experience it is possible to use small portable gas generators and get clean audio tracks if you have the right equipment and know how to use it. First off, if you are shooting in the desert at night and your lighting load is 1950 Watts your going to need a larger generator because you are sure to have additional loads like monitors, lap tops, hard drives, battery chargers, not to mention a coffee maker and work light so that crew can find the coffee. All these loads add up quickly, so you will need a larger generator. But larger generators create more noise, which makes it even more important that you have the right equipment.

I would recommend a Honda EU6500is inverter generator with a 240V-to-120V step down transformer. The Honda EU6500is inverter generator to begin with is much quieter than the 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 EU6500is substantially quieter than the conventional ES6500 model.

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 a Crawford 1400A movie blimped generator. But, where you wouldn't try to park a Crawford right on set in the middle of the desert and record sound, you shouldn’t try to record sound with a Honda EU6500is right on set. To record sound without picking up generator noise all you need is a 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.

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.​

To record sync sound without picking up any generator noise, run the generator out of the back of a van or truck with 200’ of extension cable between the generator and a 240-to-120 step-down transformer that doubles as your distro box. This is usually enough cable to place the van or truck far enough away that, with the additional blimping you get from enclosing it in the Van/Truck, you won’t hear the generator on your audio tracks. Use a heavy-duty 250V cable between the generator and transformer so that you eliminate the voltage drop you would have using standard electrical cords.

60A GPC (Bates) Splitters and Woodhead Box.​

To assure full line level (120V) on set, use a boost transformer designed to compensate for line loss. That is, it is designed to slightly boost the voltage on the load side (secondary) so that 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 far from set where you won't hear it, yet assure that the supply voltage on set does not drop too low.

60A Woodhead Box running Power-to-Light PFC 800W ballast (left) and PFC 1200W ballast (right.)​

There are numerous other reasons to use a transformer in a situation like this. For more detailed information on the use of transformers for set power, I suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture production. Use this link -
www.screenlightandgrip.com/html/emailnewsletter_generators.html - for more information about using inverter generators with transformers for motion picture lighting.

Guy Holt, Gaffer, ScreenLight & Grip , Boston

 

[Chris Santucci]

Good God.

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[pixelated]

Sweet - Thanks for sharing Guy.