I'm sure this has been done by many here, in many different ways, but since I had the photos ... It's simply a standard LM317 voltage regulation circuit (http://diyaudioprojects.com/Technical/V ... Regulator/) placed inside a BP511 case.

I dismantled an old BP511 battery - very interesting it was too - and simply fitted in the circuit. The output wires are soldered directly to the BP511 +/- tabs. The incoming 12v power line (with JST connector) comes in via a hole, and a zip-tie is used as a strain relief. The hole is cunningly positioned to mimic the cable routing from Canon's own DC adapter.

The large capacitor is simply a charge reservoir that supplements the current draw when the LM317 by itself (max 1.5Amps) is incapable of sating the camera's thirst. Simply using an LM338 instead (which I didn't have) would obviate the need for the capacitor, as it can pass 5Amps. I must say that the capacitor fits the battery case beautifully.

The obvious concern is the power dissipated (as heat) by the LM317 (P = 5volt drop * current <= 1.5Watts) which now occurs inside the battery compartment. If you're in Antarctica this may be a good thing ... I find that the heat generated isn't a problem provided the camera isn't constantly working hard.

Digital Rebel, basic time-averaged current draw:
Boot: 130-250mA
Idle: 100mA (if you use power-down feature it will eventually drop to <<1mA)
Pretrigger (half-press): ~200mA (+ ~50mA for AF). Lasts for 10seconds before returning to Idle mode.
Trigger (full-press): ~200mA
Using menu: 200mA
Preview: 200mA, 300mA while reading CF card.

There are of course momentary current spikes, reputed to be >1.5amps, which is why the LM317 is not an ideal choice. Nevertheless these ICs are excellent, and a must-have for even the beginner. They also function as current regulators (see link above), which I have used in some special dimmable-LED time-lapse lighting I built recently, and will describe in a post at some point in the near future.

I know this will make most of you wince, but I recently read that a chap had bravely run his dSLR directly from 12v, without any conversion, and without any trouble. The camera's built-in voltage regulation seemed to be able to take the load, although I'm pretty sure he was just taking occasional photos, not time-lapses.

Great idea putting the regulator inside an old battery. Would work well in the cold I would think.
It's a lot easier (and effective) to heat the camera from inside than outside.
Less wires to worry about too.

Cool design - I like it!

!c

I just took 1300 photos of a raccoon in a box, powered by this thing. 6 sec intervals. The thing wasn't especially hot afterward, just a little warm. 60'F ambient temps. No missed shots or corrupt CF writes. Shall certainly make more.

I wonder if there should be a repository thread for the power consumption of different camera bodies in various modes. Might be useful.

Hi Guys ! could I just use one of these at http://www.harbortronics.com/detail.php?id=45 instead of doing the DIY stuff ?

8.5 volts is a bit high, but would probably still be OK.

For a better value for money solution in NZ, pop into your nearest Dick Smith Electronics store or order on line one of these...
http://www.dse.co.nz/dse.shop/49eacc6b0 ... View/M9889

I have been using a couple of them for a few years now without any problems. Just set them to 7.5 volts, and away you go.

Thanks for that, will do tomorrow! By the way what time zone are you in down there? I guess you pass through Christchurch as well? Let me know if you do and have some spare time

We actually own a house in Christchurch, and split our time between NZ & California when we are not on the Ice.
I'm a Taranaki lad originally, my wife is from California. We'll be back in NZ in October after the winter.

@astronomerroyal

Hi!
Could you post some images again, please?
I'm trying build something like that, but I need some ideas...

Thanks!