Home of Professional Cinematography since 1996
Published : 7th April 2004
Wow, it's been a while since I've been here. Like the new layout A LOT!
Anyway, on to business. I'm in the process of building a prototype 13/26v camera block battery, similar in performance to the Dolly Packs. These batteries are really nice, but OUCH! they are super expensive, like over $1600, and that’s WITHOUT a charger!
I'm probably not going to go for the custom packaging like the dolly packs, and I'm still debating installing a meter of some sort, but the real question is this:
Where can I find the electrical current draw on various film cameras from Arri, Panavision, Moviecam, etc? I know they're all the newer cameras run on 24v, but I'm looking for the amp draw specs so I can provide them to my battery designer to install the proper fuse protection. I've checked arri.com and taken a look at the manuals, but can't find anything beyond the voltage.
The battery will be small and lightweight, a big improvement over the leviathon lead acid batteries I'm used to using! Thanks in advance for any info or for pointing me in the right direction.
Where can I find the electrical current draw on various film cameras from Arri, Panavision, Moviecam, etc?
You need to know that Panavision and Arri are wired differently. Arri will use pin 1 as a ground and Panavision will use pin 1 as 24 volts positive at the batteries. If your batteries were wired the same you would have to configure specific cables for specific cameras. Since they use different connectors on the camera end this might not be a problem. Just remember you would have to use YOUR cables with YOUR batteries.
Otherwise you'll start blowing fuses in the camera bodies.
First Assistant Camera
It's important to know that any film camera will draw a lot more when first starting up then when running steady. I think a call to any rental house should tell you the answer to your question. If they don't know offhand then they should be able to check in just a few seconds.
>If your batteries were wired the same you would have to configure >specific cables for specific cameras...
Exactly what I would do. I will no doubt wire the batt based on the Arris, and build a little Panavision pigtail adapter to turn the wiring right. That way I can use the pany cables that come with the camera.
If I get this thing working and it turns out to be a viable sales opportunity, I'm sure I'll investigate wiring batteries for Pany only.
Christopher Ratledge wrote :
>I will no doubt wire the batt based on the Arris, and build a little >Panavision pigtail
This is not a good move, in my opinion.
It is too simple for someone to forget the pigtail. Granted it is quicker, but. There Are two ways I would go.
First, wire the batteries with two separate outputs, one Pana and one Arri. THEN mark each one, and fashion a steel plate that can be SCREWED over the one you don't want to use. Ideally you will know the job before hand. This has advantages and disadvantages.
The other way, which may be more appealing, is to wire the battery, using a different plug than a 3-pin or 4 pin or 5 pin XLR. Something that is not too standard. Then create an Arri pigtail, and a Pana pigtail. This way a Pigtail MUST always be used to plug in to the battery. Color code the different pigtails, and Put a matching color code on the battery. Quicker changeover in the field in case of body swapping. Plus using a NON standard battery power plug will prevent some accidental crossing of polarity.
One more thing, how about circuit breakers instead of fuses? Push reset ones, not the automatic reset ones.
Best of luck.
Cinematographer - Gladstone Films
Cinematography Mailing List - East Coast List Administrator
Better off Broadcast (B.O.B.)
New York, U.S.A.
This will vary depending on a lot of things such as type of camera, frame rate, how much film is loaded, what accessories are being run from the camera (eg video tap, senders, on board monitors, etc). A lot of things to consider! Check existing systems to see what size fuses are used.
From memory, an Arri 35-3 draws about 3.2 - 3.5 amps running at 24 frames. hmmm, can't remember any others...
Don't forget the humble eyepiece heater they can pull juice big time. Just a thought with the fuse/breaker options can anybody fault the idea of actually putting the fuse or breaker in line of the power cable/pigtail?
Then it wouldn't matter what or who's battery you were using, it would always be protecting the camera.
In testing in the shop I have found a consistent rate for watts per perf. An 8 perf camera running at 24 draws twice the power of a 4 perf camera. Our Arri 3 peaks at 8 amps when ramping to 120FPS and settles around 4 amps at 120FPS.
I design and build the battery packs for a VFX house. I put 9 Amp poly switches in our packs for output protection. These are auto reset circuit breakers.
As for connectors, I wire my 3 pin XLR connectors to the Panavision standard of pin 1 + and pin 2 -. This is backwards for the way those connectors were designed, but who is to argue with Panavision. I mark the pack with the pinouts and expect the AC to have a clue. (Generally our packs go with our gear and our AC's so this isn't much of a problem.)
I use the Canon brand XLR connector, these have a rubber insert that does not shatter like the Switchcraft or Neutrik. I also remove the latch from the female connector on the pack. The Cannon connector has a high retention force so your cable won't fall out. if it gets jerked hard it comes unplugged instead of ripping the end off the cable.
As for battery cables I use the Neutrik connectors on the cables. These have a collet type clamp to grip the cable and no screws to fall out or get loose. They also have coloured boots available for color coding of multiple cables. (Think Camera and Flat Base) I have also been using the coloured boots to designate 3 pin and 4 pin cables, Orange for 3 and Yellow for 4.
Be sure your cells are welded together and have a good shrink wrap around them. I call out XL-PVC type wire for the packs and use that for internal wiring, it does not melt if there is an overload or other fault.
Here are some links for parts (you may need to unwrap the links) : female connector on the battery pack :
Neutrik connectors for cables :