Hi Eric
Many thanks. Just the kind of practical information I needed. Invaluable.

Thanks for posting this as well Eric.

BTW, can one extend the cable length without affecting the current flow?

Maybe a 16' cigarette to 4-pin XLR + 20' 4-pin XLR to 4-pin XLR?

16' would be a bit short in certain situations.

I think as long as you use like a 16 gauge zip cord as your cable, it shouldn't be a problem. Even 18g might work but I think 16 gauge would give much less drop over that length.

*disclaimer* It's been years since I've performed a voltage drop test. If something or everything I mention below is wrong please let me know so I can fix my mistakes or delete parts of my post.

I'm not nearly so good on this part. If you want to run a longer cable and not have much of a voltage drop you will need a thicker gauge wire (make sure its the wire gauge that is thicker, along with having more strands. In other words make sure the shielding is not the only thing that is thicker.).
To determine if you need a bigger gauge wire(wire will be listed with by the smaller the wire gauge the larger the conductor....example a 16 gauge wire has a thicker conductor than a 20 gauge wire) perform a voltage drop test. Take a volt meter and put one of the probes on say, the positive terminal of the battery, and put the other probe right before the load which would be the light in this case(still on the same positive cable). If you see a reading of more than .4 according to How To Perform A Voltage Drop Test - Help With Automotive Circuit Diagnosis you have to much resistance in your wiring and need to step up to a larger gauge wire.

Wow, maybe I shouldn't have given all this information out, it looks like I could have started selling my own DC 4 pin XLR power supplies. Well, Bescor already sells the battery belts with a 4pin XLR.


Hope this helps.

Edit: Richard beat me to the post with a much simpler answer.

All good information Eric. I definitely wouldn't bother with shielded cable for a power run since this is DC there's no high frequency to protect against thus no noise to worry about. That would be wasted so just the 16g unshielded zip cord should be fine.

On the subject of voltage drop, you definitely want to make sure it doesn't drop much below 10VDC if you're making a custom cable, as that's the base where the panel wouldn't function anymore. We'll go down to 10VDC but not much lower than that.

I would plan on using this LED off of the cigarette plug on my Bescor battery belt as the 4-pin would be in use powering the camera.

Richard,

Would you be able to make a 30' cigarette plug to 4-pin XLR cable?

(Probably) not a problem Tim. I would of course want to test that to make sure the voltage drop wasn't too severe but I'm betting its okay. Would be an interesting experiment anyway.

For anyone interested in cobbling together their own 12-volt batteries, here's how I created my own.

The pack consists of four A123 Systems batteries taken from a DeWalt nano-phosphate battery pack. You can also get these batteries directly from A123 Systems as a "developers kit": Developer Kit, ANR26650M1 High Power Lithium Ion Cells

A developers kit comes with six batteries. To get an hour of light for the CoolLights LED, you'll need eight to provide enough watt-hours.

These batteries have high energy density, allow a lot of charge/recharge cycles (more than 1,000) and are much safer than lithium-ion or lithium polymer batteries. There was a demonstration where a drill was driven right through a fully charged battery. Any other lithium battery would have burst into flames and possibly explode. But the A123 battery just smoked a bit.

I built a pack of four batteries, connected in series, for a total voltage of 13.2 volts, 2.3 amp-hours. These batteries can provide up to 120 amps for 10 seconds so be very, very careful not to short them! It's also possible to combine two packs of four batteries to get 13.2 volts and 4.6 amp-hours.

There are "balance taps" for each cell. A balance charger from FMA Direct charges each cell individually and monitors voltage for a precise charge. This maximizes battery life. I'm using a Cellpro charger: FMA Direct : Product Detail

There's also a Cellpro charger that can handle up to 10 cells: FMA Direct : Cellpro 10s Charger

After soldering the tabs and connecting the balance taps, I wrapped the pack with thin foam sheet and heat shrink. I built two of these and power a variety of things including a small LCD monitor and an on-camera LED light.

Much of this comes from the radio-controlled airplane/helicoper industry. They're always looking for solutions that provide a lot of power with the least amount of weight.

Just to clarify. You will need 8 batteries, not 8 developer kits.
Four batteries wired together in series would give you about 30.36Whr and weigh in at 70g or 0.62lbs....plus weight of the case.

For a setup that would last about 2 hours or have 91.08Whr this would run $220(for two developer kits) + extra for the charger, and would weigh 840g or 1.85lbs.


Going this route would be cheaper and lighter than buying a pro battery. You won't get the LCD power meter like the pro batteries have unless you make one yourself though.

Actually, you might want to look at the Bescor battery belts at B&H.

They have one that goes up to 288 watt hours for $199

Bescor | PRB-24XLRATM Heavy Duty Starved | PRB24XLRATM | B&H

I have used a smaller version for 4 years now for 1/10th the price of an Anton Bauer setup and longer running times.

I ordered two of the LED600's and like Dean said I have alot of A123 batteries in various configurations from RC Helicopters. What I wonder is, if an 8S 28.8v (29.2V hot off the charger) will be more efficient than a 4S 14.4v battery. Higher voltage should reduce the amp draw but then there might be a loss of energy from the voltage being regulated to whatever the native voltage is. Any thoughts?

The DC to DC converter is only good up to 24v so I wouldn't run it past that.

Kevin...

I'm messing around a little with RC helicopters, too. That's how I came across the nano phosphate batteries.

These LED lights don't draw amps like helicopters. So higher voltages don't really buy you any additional efficiency advantages. In theory, you don't get something for nothing. So it's either amps and volts, or volts and amps. The transitive properties of multiplication is the same in either direction. So with a given wattage, it won't matter which is which. Just keep in mind that there is a voltage limit.

Is the input voltage exactly 12V to 24V? This would rule out the use of 24V batteries. A 24V SLA battery charges to 29.4V and settles around 26-27V which is slightly higher than the voltage from an 8S A123 pack.


Thanks

Actually at the design level a higher voltage could be advantageous for various reasons of efficiency but once the design is locked in, its set in stone what the input voltage is to such a panel. In this case, 10vdc to 24vdc is the range you can input, which is already not too bad. Otherwise, you're absolutely right on the explanations about how everything equalizes out.