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#1 Daniel Madsen

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Posted 18 March 2006 - 06:16 PM

With little money film students still like shooting on location- duh. As a gaffer and DP in training I would like to provide my comrades with a power option other than a generator.

Could someone please describe how they use a car battery to accomplish this. Do you connect an invertor directly into a cigarette lighter (easy to charge the battery that way) or do they make invertors that clamp onto the positive and negative terminals of a battery? How do you connect mulitple batteries up to the same invertor?


I don't want to hear why a small generator by so and so is a much better option. In fact the word generator is not allowed in your reply :)


Dan
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#2 Trevor Greenfield

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Posted 18 March 2006 - 06:54 PM

Sure you can connect an invertor straight to a battery. I have done this many times for camera power (giving hours if not days of shooting power before recharging), and a couple of times to run small lights from a little 12v gel cell.

Of course this is impossible with an HMI as an HMI requires a very specific and sync power source. Also, you have to consider the amperage draw on a 12v from a larger non HMI like a 500, 650 or 1000 tungsten or even halogen. Also to consider is that a generator or wall outlet will provide a much cleaner sine wave of energy than a battery through an inverter. Lights wise I don't know how this plays out but I would assume especially flo's like clean power. Sync cameras however, can have real problems getting sync without clean power.

So, If you are talking about a few practicals, I'd say 100% go for it, but if you are talking about running a 1k or something, well, someone here will probably say that its not a good idea.
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#3 Chris Keth

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Posted 18 March 2006 - 10:25 PM

I don't think it's such a good idea, unless you're just running a few very small things. I've run a teenie-weenie (the 30v DC kind) off of a battery belt before and it only had juice for maybe 20 minutes of shooting. It was spectacularly short lived. I doubt a car battery would be that much better.
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#4 timHealy

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Posted 18 March 2006 - 11:44 PM

You can get a true sine wave inverter 120 v AC from 12 v DC that works with small HMI's, tungsten and kino flos like the one here:

http://www.starmarin...er|Charger.html

They work really great.

Of course the amount of time a battery will last depends on the amount of light you try to use. You can however connect as many 12v batteries with the inverter as you like as long as you wire them up in parrallel.

A typical setup will have two car batteries hooked up to an inverter. They can work really great. But keep an eye on the voltage.

You can create 120 volts DC with 10 - 12v batteries wired up in series for use with tungsten only.

It is best to keep the amperage draw low and to keep the lights off when not shooting.


Best

Tim

Edited by heel_e, 18 March 2006 - 11:49 PM.

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#5 Cole Webley

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Posted 19 March 2006 - 03:23 AM

Hooked an inverter to a car battery and ran some peppers hanging outside the car shooting back in on driver simulating passing lights--worked great for about two hours--make sure you kill the lights between takes and don't put anything on top of those inverters they HAVE to breath or they will die. Also, a little inconvinient if the battery and inverter are inside the car you are trying to take sound from--sounds like a lab top computer fan, a little loud when trying to get clean sound. Peppers where pretty small, I believe we ran three at one time and nothing over 350w.

Best of luck.
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#6 Rik Andino

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Posted 19 March 2006 - 05:39 AM

You can get a true sine wave inverter 120 v AC from 12 v DC that works with small HMI's, tungsten and kino flos like the one here:

http://www.starmarin...er|Charger.html

They work really great.

Tim


Sound like a cool idea...but for the price of this set up you can get a putt-putt
It'll have the same wattage as the inverter and is easier to refuel than charging batteries.

There is a reason most productions use gennys
They're more efficient, there's no way around it...

However if you're up in a pinch and only have two bucks (maybe you shouldn't be making films...)
You can use a 1KW inverter and power some Kinos and few standard scoops and get a quick scene.

The battery power doesn't last long enough...so you must be quick.
You do two takes and go for a reverse and there you've drained all your power
Find yourself muttering "We' should've just spent the money on a genny..."

I know you don;t want to read the generator on this thread
but I'm just saying there's a reason inverters aren't even popular on low-budget sets.

But don't take our word for it...go find out for yourself.


Good Luck
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#7 Alessandro Machi

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Posted 19 March 2006 - 06:22 AM

I switched to all battery for lighting when I had no help and the producer wanted to move around a lot in a short amount of time. It's amazing how much time I saved not having to find new outlets for the extension cords.

I have my motorcycle style (although they are bigger) batteries wired for four pin so I can charge them rather quickly after a shoot, even though they are lead. You MUST add a fuseable link in the battery circuit as this helps reduce the possibility of a battery malfunction which can lead to an explosion.

The biggest thing you lose is generally battery operated lights are not focusable, what you gain is the battery can stay at the base of the light stand and can be moved to a new spot very quickly.
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#8 Matt Sandstrom

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Posted 19 March 2006 - 10:21 AM

a related question, anybody knows how much "extra wattage" the alternator outputs, i.e. how much can you run off the regular car battery while driving or idling without draining it?

/matt
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#9 Freya Black

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Posted 19 March 2006 - 12:26 PM

However if you're up in a pinch and only have two bucks (maybe you shouldn't be making films...)


ooooh! That's a terrible thing to say. Personally I really like a lot of low budget movies, although two bucks will admittedly only buy you a sandwich. :(

I think it's okay for people to try and make films with no money, just as long as the two bucks is not also the only money you have to buy food, pay rent etc. Although if it is then you are in deep trouble and probably have long since forgotten about your film. ;)

love

Freya
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#10 Mark Dunn

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Posted 21 March 2006 - 06:33 AM

A car alternator puts out about 600W at medium revs but only about 200 at idle. Don't even think about disconnecting the battery to use the alternator output directly. The car electronics and engine control unit will object expensively. Unless you have an old car, in which case you have a decent unblimped genny.
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#11 timHealy

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Posted 21 March 2006 - 09:56 AM

Sound like a cool idea...but for the price of this set up you can get a putt-putt
It'll have the same wattage as the inverter and is easier to refuel than charging batteries.

There is a reason most productions use gennys
They're more efficient, there's no way around it...

However if you're up in a pinch and only have two bucks (maybe you shouldn't be making films...)
You can use a 1KW inverter and power some Kinos and few standard scoops and get a quick scene.

The battery power doesn't last long enough...so you must be quick.
You do two takes and go for a reverse and there you've drained all your power
Find yourself muttering "We' should've just spent the money on a genny..."

I know you don;t want to read the generator on this thread
but I'm just saying there's a reason inverters aren't even popular on low-budget sets.

But don't take our word for it...go find out for yourself.
Good Luck


Actually It is a great idea for both small shoots and large, and it depends on your needs. Car batteries can last much longer than the two or three shot scenerio if they are good and fully charged. I use them all the time.

Of course a generator can always work better and last longer than batteries and an inverter. But you have to deal with the noise, refueling and keeping it well ventilated which typically means rigging it outside of the moving vehicle. In many cases you'll need grips and rigging equipment.

An inverter and batteries are ideal when you don't have a place for a generator nor the electrical need. Typically you just hook them up in a trunk and run a 12/3 or zip extension outside the car. It can be very fast as long as your lights are small. And as long as you turn them off between takes, they will last some time. A typical set up will use two 12 volt batteries at a time and smart electricians will have a few extra batteries on hand.

For examlpe, I worked on War of the Worlds last year and both systems were used as the needs changed. When only using Kino Flos, the inverter and batteries worked just perfectly. When they wanted to do a CU of Dakota Fanning in the car with everything burning outside of it, we used a bunch of uncorrected 1k nuke lights and of course that meant a real genny was needed, so the grips rigged a platform off the van where the electricians placed a 6500 genny on it.

It is not a matter of which will work all the time, it is a matter of which is appropriate. Either way will work just fine. So it depends on the needs for your particular shot.

The only caveat is that David Mullen mentioned a while back that small HMI's may have gone a little green on him using an inverter.

Also, unless you are a car mechanic or have one on hand, I would stay away from tapping into the battery or alternator of the picture car you may be using. Or limiting the power you tap off the picture car to a small Radio Shack like inverter that plugs into the lighter socket. Something in the 200 to 400 watt range. If you put too much of a draw on it you could deplete the car battery and be left by the side of the road. One thing thought, larger vehicles like ambulances and small buses typically have larger alternators with higher output than normal cars.

Best

Tim

Edited by heel_e, 21 March 2006 - 10:00 AM.

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