Battery pack options for sumix cam+minicomputer?
 

Hi all,

As some of you know, I just bought a Sumix 12A2C cam. I'm also planning to buy a MiniITX based computer, a mattebox, a follow focus unit, an external HDD, a 7" touchscreen lcd and a rod support so I can assembly a complete independent digital cinema cam. Since both the cam and the computer have standard power plugs I should have no problem shooting anything indoors. Outdoor shooting shouldn't be a problem either as long as I can have a car near to plug the cam to. Now imagine I have to shoot a scene in a little street in the city center where I can't have a car stopped or a generator running (mainly because of the noise).

My question is: what are the options I have in terms of rechargeable battery packs for both the computer and the cam?

I'm sure others might want to argue differently, but I was looking at using NiMH batteries in a belt pack. I thought that lithium ion would work better but the cost is high and can be difficult to find a good solution that gets you the right voltages. Plus, they *can* explode if over-loaded.
The NiMH on the other hand can be combined into sets of parallel wired in series to get you as much power as you are willing to carry. You also don't need to worry about getting consultation from an electrical engineer.

I am planning to use anton bauer batteries, they are very standard in the film industry so you can easilly borrow a battery from someone else.

But they tend to be a bit expensive. It costs me around 1200 euros for a complete set: battery, charger, battery-mount. But for me the battery should be able to power the Pike for 10 hours, I also plan to power a viewfinder and trigger electronics with it as well.

By the way Take, I'm also looking for a viewfinder too. What are the options?

And how can I calculate the power consumption for the computer and the cam? I need that info to choose the battery pack.

I think I will just buy one of those cheap LCD panels (to bad oled is not available yet). I do not need much of a user interface, as there is nothing to configure, so I can get a sun hood for it.

You could power it using an power adapter and measure the amperage through the computer/camera/viewfinder combination. just multiply amperage by the amount of hours you want to run it for how much Ah you need for a battery (at a given voltage).

Cheers,
Take

If cost is a major concern, there has been decent feedback (on a different forum) regarding some of the cheaper Hong Kong Li-Ion batteries that can be found on eBay, such as this one...

http://cgi.ebay.com/12V-5VDC-Super-r...QQcmdZViewItem

They are available with or without a 5V powered USB port, and are typically 12V and 1800mAh. Several in parallel should yield similar results to an Anton Bauer pack.

At between $9 USD and $19 USD each, the cost is significantly less.

If you have settled on a configuration for the minicomputer, it should be relatively easy to estimate your power requirements... but I think that a you may be able to get away with using a 60 watt power supply, unless you are planning on using a very hungry graphics card. You will want to use a power supply that has a wide range of input voltages (such as 6-24 volts), to account for the voltage drop as the batteries discharge.

That means, if my math is right (converting the Amp-hours to watt-hours), 3 of the eBay batteries in parallel should be able to power a 60 watt supply for about an hour. Though you may want to go with 4 batteries and an 80 watt supply in order to make sure there is enough power for the LCD.

Take a look at these ones:

http://www.batteryspace.com/index.as...S&Category=521

The highest price is about $400 but they look good... What do you think?

In the past I have used car batteries and a 1500w inverter to power computers and other on set equipment (monitors, sound, laptops, and even lights). I can run a quad core desktop pc, camera, and lcd for about 40-50 min off 1 car battery. Its possible to chain them to provide more.

Also at times I use the inverter on a running car to provide constant power.

Now I own generators so when power is not available I just use them.

I don't do any 'run and gun' filming so this is never a problem for me. However, obviously not the best solution for everybody.

We also have a small generator but it's very noisy, so we can't use it in certain places, plus having a portable rechargeable battery means we can shoot almost anywhere.

I just received an email from Batteryspace asking for more info about the setup. I gave them the specs for the computer, the lcd and the camera. Let's see if I can get something interesting from them.

For the 400, I'd think you'll get more than enough power. I'd guess you might see upwards of 8 hours or more with 20Ah. My guess at wattage would probably be around 250 W peak, so it could realistically be more. If your very careful with parts selection i.e. lower power cpu and say 2 HDDs, with one of those tine power supplies for itx, you could maybe see peak power under 75W for the computer.

What are you using for input devices? I felt weird about the idea of the on-screen keyboard, but a small track would do for most of the time.