External battery pack for D200 (not MB-D200 grip)?

I am thinking of rigging an external battery pack for my D200. I have the

MB-D200, but that weighs 270g without batteries and makes my camera too big. The

EH-6 AC charger supplies 13.7V through a proprietary plug. Therefore, I figure

an external battery pack using 9 AA lithiums would provide 13.5V, 41 watt-hours,

and weigh 130g (excluding the battery holder and wire) or 200g with alkalines.

This compares to 11 WH with a single ENEL3e battery, which gives ~300 shots, so

the battery pack should give about 1000 shots. I would need to buy an EH-6

adapter, cut the plug off, and hook it up to the battery pack. The external pack

would also be useful for cold weather, where the batteries can be kept warm in a

coat pocket. This was done for the D1 by Peter Wolf, though using a lead acid

battery (http://www.robgalbraith.com/bins/content_page.asp?cid=7-3731-3741).

Buying the adapter just for the plug makes it one expensive plug. Is there any

way this could mess up my camera (other than by getting the polarity wrong)?

Will the camera have trouble if voltage levels drop as the batteries are used

up? Anyone try this for the D200?

Why go through all that ?

Just get a Digital Battery Pack (40 watts) and the D2x/D200 power adapter and plug that into the side of the camera - enough for 5000 shots +.

Where do you get the digital battery pack and the D2x/D200 power adapter? I couldn't find anything like that when I looked.

Will look at different cell chemistries. BTW, Energizer has great data sheets. Their lithium AA L91 is LiFeS2. Voltage can be from 1.6 (new) to around 1.2V before dropping, so 9 batteries are 14.4V to 10.8V. Not sure how sensitive the D200 is on this port.

Quantum makes an external battery pack and cord that work with the D200. The SD10 cable is $52 @ B+H and their battery packs are on the order of $500(!) The EH-6 is "only" $75.

Rigging up the battery to a voltage regulator would solve any fears of damaging the camera, particularly due to over voltage. Some research led me from the old trusty LM317 to adjustable low dropout voltage regulators. Sensitron make the 3A 1V to 1.5V dropout SHD526150 and a 2A version SHD520130 (http://www.sensitron.com/searchresult_10.asp?type=5.3); there is also a 5A version but it would be overkill. This is better than the 2 to 2.5V dropout of the LM317, though not nearly as good as lower power supplies. Dropout voltage on the Sensitron regulators depends on output current. The bottom of my D200 shows the DC voltage requirements as 7.4/13.5V 2.5/2.5A. Now it seems a bit strange that the same current requirement would present for both voltages, the 13.5V should have a lower current requirement, but at least the 3A regulator can provide both.

Looking at the Energizer datasheet for the L91 lithium AA battery, the digital camera test has the battery maintaining a reasonably stable voltage of 1.3 to 1.2V before the rate of decline significantly increases. So let's say the battery works between 1.6 and 1.2V, and we have a dropout voltage of 1V (typical) and need to supply 13.5V, then we need 12 AA L91 batteries. Each L91 weighs 14.5g, so the batteries altogether would weigh 174g.

Battery Junction http://www.batteryjunction.com sells the L91 for $1.85 to $1.95, and batteries from Nuon for $1.24, though I have no chemistry data for the Nuon. So 12 batteries at $1.9 is $22.8, plus the voltage regulator, AA case ($5?), a couple of resistors, some wire, and 3 DC jacks/plugs ($10?) is all the hardware and battery that's needed. Throw in an EH-6 supply for $75, and you have a grand total of around $113, plus shipping and a bit of labor.

Why this obsession with AA batteries? Because I can get them in most of the world and they have a good mAh rating to voltage ratio. Also, if I don't need the extra power I don't have to carry the batteries around with me, no charger to carry, and I could use them for running a flash.

I think this could work. Now I should really get to sleep!

Silly question, but if you need 1000 shots, what's wrong with popping two fully charged EN-EL3e into your pocket?

Sure you have to change batteries twice during the course of the shoot, but is that anywhere near the hassle of having a battery pack strapped to your camera (and you'll find that by the time you manage to attach the batteries together to make a stable "pack" and then attach it to the camera in a way that won't interfere with however you want to grip the camera or block the tripod socket, that you've run up way more than the 130g you're looking at.

The "digital camera battery" that Mitch mentioned weighs 650g for the 40W-H NiMH unit. The Quantum is similar. And you're dealing with cable from belt pack to camera.

Now, here's a thought... If you're using the camera up to your eye for large runs of shots, turn off the image review, then when you do take the camera away from your eye, you can bring up images with a touch of the play button. The D200 can easily do 600+ images on a single EN-EL3e with the preview off most of the time, instead of on for a few seconds after every shot.

What about something like this:

http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID=17894

Coupled with the Nikon AC cord, it looks like it may give several hours of portable power for under $200 total.

Cheers,

Rob

I had another thought....

The external AC power supply (the EH6) has an output of DC 13.5V/5.0A. So if one can put together a portable battery source that outputs at 13.5V/5.0A, AND get the right plug to fit the D200 body, then that should work, no?

Then again, I may be showing my lack of knowledge regarding electronics.....

I found this article because I'm trying to do the same thing. That is, come up with a portable power solution for my D200. I use the MB-D200 for general shooting and I carry spare ENEL3e's in my bag. What I really need the external power supply for is my time lapse photography. When doing long exposures on the beach at night, I used up 2 fully charged ENEL3e's in 2 hours, and just over 200 images. Here is the result of that shoot:

I would like to make up a battery pack that I can hang from my tripod and power the camera for 8 hours or more of shooting. I'm not as concerned with the weight but it does need to be light enough to carry in a backpack on short hikes.

I recently did a time lapse job for a construction company. I used 2 deep cycle golf cart batteries, an inverter and the EH-6. I got 48 hours of continuous power to my D200 and a laptop connected to the camera. Those golf cart batteries are heavy! It would be really difficult to carry them down to the beach. Also, converting 12v to 110v to power an inverter with a cooling fan, etc. to power another transformer that steps the voltage back down to 13.5v, seems inefficient.

I do have a suggestion about not "wasting" a perfectly good EH-6. Cut the low voltage cord in half and splice in a male and female connector from Radio Shack. This way, you can still use the camera connector for the EH-6 and also for whatever battery pack one of us comes up with.

Any more ideas?

I just spent another half hour searching Google and couldn't find anything new but I just had an idea...

Forget using the EH-6 plug. What if you took the AA battery adapter that comes with the MB-D200 and wired an external cable to it? At the other end of the cable, you could attach any number of other battery types as long as the voltage is 9v, right?