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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Building my own battery...

B

Brook Willard

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Hey guys,

It's no secret that I'm planning on getting the RED onto a helmet for some skydiving. I've been laying the groundwork for a while [getting a camera owner who's willing, getting a talented enough camera flyer, securing lenses, etc.] and it's come time for me to build a battery solution for the camera.

As it stands, the combination of a RED V-mount plate and a RED BRICK would add several pounds and a lot of volume to a helmet-mounted camera system. It just won't cut it.

Here are a few pictures of the style helmet we'll be using with the camera:

5_1199688201.jpg

5_1199688239.jpg


It's a big helmet, but the RED will take up the entire top. It's the only thing I want outside the helmet. Extra stuff outside the helmet raises the CG of the helmet [neck strain during deployment] and adds snag points [suspension lines + snag points = bad].

My plan is to build a battery that can fit on the inside of the helmet in the space above the jumper's forehead. I was considering building my own batteries from scratch by either putting cells together or making some brick of disposable batteries, but a little thinking dumped me on airsoft gun batteries.

They come in several varieties including 12V. They come in ranges from about 600mAh to 4,200mAh.

5_1199688436.jpg


This is a 1,500mAh 12v battery that would fit nicely into that forehead space. That's an 18WH battery [vs. the RED BRICK's 140]. A 4,200mAh battery would be 50.4WH.

They use this little connector for power:

5_1199688530.jpeg


I have one LEMO connector for the power left over from the four I originally got from RED [somebody stole the other three from my car, but that's another story...]. I'm thinking about making a very short "dongle" that I can plug onto the back of the camera that will go from the LEMO to this little plastic connector. That way I could use a softer, more flexible and cheaper cable to run from outside the helmet to inside.

Lighter cable means less flapping, though it does increase the chances of failure. I dig this connecter because it's cheap, easy to find and replace, easy to throw together and tiny. An XLR [even a mini-XLR] wouldn't cut it. If the camera comes off of the helmet in freefall or on deployment, I need this cable to fail easily... and that plastic connector will be the weakest link I can keep in the system.

So, question time. Most of these are to RED.

1. How should I wire the "dongle"? As we all know, there are two positive and two neutral pins in the LEMO. Should I make a short run of a four-core power cable from the LEMO and just solder them to the single positive and neutral leads on the airsoft battery connector? Is there any kind of even current split between those pins in the LEMO, or will the wonders of copper figure it out for me?

2. Will the camera even run on a 1,500mAh [18WH] battery? Airsoft batteries tend to be capable of supporting pretty impressive amperage draws... think it'd work? What does the camera draw sans LCD and EVF? Just the camera recording to CF.

3. Is there something I'm missing? We're just talking copper here...
 
Brook, First thing is to determine the actual current draw of the camera in Record mode at what ever frame rate you will be recording at. I'm guesstimating at least 5-6 Amps. You will have to have a power source capable of delivering that kind of grunt for the duration of rec time 4-5 minutes?

My first thought is is some sort of Belt battery with the cable running inside your flight suit so as to not interfere with any cord deployment or control. IDX has the C-EB which has a short cable with XLR. The 2 Pin MOLEX connector you are showing may not be able to handle the current. There is a connector used in two way communications that will handle the current called Anderson Power Pole. These will also pull away as they do not have any locking mechanism as the MOLEX connector does, and will handle the current. In the event of having to abort and eject the helmet, the power pole will easily pull away. The power pole is fairly priced, the crimp tool is about $45.00. Stop by Ham Radio Outlet 933 N Euclid, Anaheim, 714 533.7373, talk with Janet, to look at these.

For short run, I would imagine a length of CAROL SJO 18/2 or 16/2 will be enough. Call Art at Pacific Radio in Hollywood, 323 969.2035 to source this.

On wiring the LEMO, as long as Pins 1/2 (B+) and 3/4 (B-) are connected together, you will be fine, as the current will be divided between the pins as specified. Solder the cable between the two pins, be sure to use heat shrink tubing for insulating.

Just be cautious of the heat generated by such a current draw, and if from a cell too small, it could result in a failure which could be dangerous at those heights.

A basic cabling idea could go like this V-Lock Battery / belt adapter - XLR M/F Connections - Length of cable to neck line - Power Pole M/F connectors - Cable - LEMO.

Hope this helps,

Wes
 
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I considered the belt battery briefly, but it's just not desirable in freefall. The added weight and complexity are both significant issues, and the connection between the helmet and user's body is not a good thing. Yes, the cable would probably break, but it's not one of those things that can be left to chance.

Using a connector that might break if the camera separates from the helmet is one thing - that's almost a "bonus" when compared to normal helmet safety. That's not generally a consideration that one makes - nobody wants the camera to come off of the helmet in the first place, so they're quite securely locked down.

Helmet cutaways do happen, though... not often, but sometimes. And when they happen, it's not a decision taken lightly: it's a life or death decision. So that helmet cutaway HAS to work the first time every time without blinking an eye. Even a slight hesitation as the helmet dangles on the body cable could be enough to further entangle the system into a malfunctioning canopy or it could strike the jumper in the head and knock him unconscious.

I'm heading into RED in 20 minutes for other reasons... I'll learn what I can learn about the power. As it stands, the airsoft batteries should be capable of outputting enough current to keep the RED happy - they're generally capable of 30A draws.

More to come...
 
I recommend looking around RC aircraft catologs. They have tons of super cool cells for building your own batts.
 
Hey Brook,

My AC rides motorcycles year round and was annoyed that his face shield on really cold days would fog up. His solution was a snowmobile helmet with a heated inner shield. Anyway, it's got a cable that runs to the bike for power. Obviously it needs to be a break away cable. The solution is a simple RCA connector for the power cord, a moderate tug and it pops right out.

I am not sure, but I think you are going to have a hard time finding a battery small enough to fit in the helmet that will deliver enough amps. Electric model airplane batteries dump some huge amps, but they get Really hot....They also sometime catch on fire......

There has got to be a middle ground between a full size belt and a Brick....Shit, just remembered these from my Nat Geo days

http://www.automatedmedia.com/products.html

Check them out, very good soulution.

Good luck,
Nick
 
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Thanks for the heads-up on AMS's batteries... they're awesome. If only they were rechargeable.

R&D time. I need a grant from RED. :)
 
Could you put the battery somewhere else instead of on the helmet? You could put it on their upper arm like the people running with ipods. GO TO A HOBBY STORE WITH RC CARS AND PLANES, or you could go to a batteries plus, they custom make batteries for everything imagineable.
 
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Having the battery on the jumper's body is not an option I'm willing to consider until I've exhausted all helmet-mounted solutions. It adds complexity, cost and risk.
 
I agree that it adds complexity, cost and risk. But on the other hand I think it will be a cool set up. If you want, I wouldn't mind taking it skiing in some of this epic powder we just got up here in Lake Tahoe...
 
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The "cool setup" thing may sound great on the ground, but it's a whole different story at 190mph. I don't mean to sound melodramatic, but these little things really can kill people.

Based on the design of some of these batteries, I have a feeling that I may be able to put them outside the helmet. The long/skinny batteries should fit on the helmet right next to the camera. I'm going to try and get out to the dropzone in the next week or so to do some preliminary fitting with a proper camera helmet. My camera helmet is way too small for the RED.

For those that are curious, here's Greg Gasson's Arri 235 setup. I'd post the full stills, but they're BTS from a feature and I don't have permission.

5_1199852319.jpg
 
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My goal is to keep the RED rig lighter than Greg's 235 rig.

Here's a better shot of his helmet:

5_1199854573.jpg


He usually attaches an Archos flash DVR to the video tap for playback. The 235 body with video tap, DVR, 200' magazine, film and battery [without a lens] weighs roughly 15lbs. The RED weighs about 10lbs and the battery should be less than one or two pounds.

If I can come up with no better solution, I'll mount the battery on the front of the helmet [where the "Get Hypoxic" logo is in the above photograph]. This should be out of the FOV of even the Arri Ultra Prime 8R he's got on the camera in that shot.
 
Thats good that you can keep it lighter than an already working product. My only concern aside from getting it cought in lines, would be the diver breaking their neck when they release their chute. But since their is already a heavier model that works, I think it will work flawlessly. This will be some awesome footage, I cant wait to see it. Are you going to be the one jumping?
 
that is a huge feat of engineering- maybe you should wait for Scarlet. :)

Seriously though- good luck with the design.
 
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Tenshredd7 said:
Thats good that you can keep it lighter than an already working product. My only concern aside from getting it cought in lines, would be the diver breaking their neck when they release their chute.
Click to expand...

I'll just say "leave it to the professionals." The safety questions that whuffos [non-skydivers] come up with are generally not to be concerned with. These guys do this for a living. :)

I won't be flying the camera. I was considering it for a period of time, but I got into a serious car accident three months ago that's put me into a slow recovery process for my neck and back. Combining 15lb helmets and physical therapy is not a good idea.

I've chatted with Greg a few times about jumping it. I've also brought it up with a few local jumpers capable of flying that kind of load, both of whom were interested.

The people are in place. All I need is the power and the camera.

I'm currently waiting on more info from RED on the camera's power requirements. I'm not willing to invest in a battery solution that isn't guaranteed to work.
 
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