gel-cel powered Canon

Unboxed the Fusion DC converter. They had one at The Source in Collingwood, when Risa and I were doing errands on the weekend. 3000 milliamps. I wanted to see if I would be able to get it to work with the Canon 40D with a 12 volt lead acid as a source.

Reviewed my notes. The stock BP-511A sticker says it outputs 7.4 volts and is rated at 1390 mAh. Steven Christenson says, on his photography tips and tricks site, like all batteries, the voltage varies. It's 8.2 when fully charged. And the camera wants 1400 mA when doing "heavy" things like running Live View. The DC Coupler says it outputs 7.8 VDC at 2.0 A.

As I looked at the Switching Power Converter, I suddenly realised there might be a bit of a problem. The unit has switch settings for 6 and 9 volts. And nothing in between. When I tested the voltage (unloaded), I saw more than coming out—not surprisingly. Sounded like I'd have to drop the voltage a bit from 9.

Reviewed voltage divider circuits, crunched the numbers, rummaged in the parts box, made a table in Excel, and built a prototype on the Electronic Lab breadboard. Saw strange numbers. Not what I was expecting. Oops. Goofed on the formula. Tried again. OK. Matched a 270 ohm resistor with the 41. That would give me around 8 volts at the tap, assuming an input of 9.2. Triple checked everything. Connected to the camera, via the coupler.

The red LED Access lamp did not blink. The sensor cleaning message did not show on the LCD monitor. The LCD panel would briefly light when I hit the backlight button. Then I noticed the Print/Share button blinking blue, faintly. Oh boy. Not a normal signature. Checked everything—again. No joy. Didn't make sense. I was giving it a voltage in the range that the AC power supply brick was. I wondered if the DC Coupler was more than met the eye. Perhaps there was something inside the dummy battery...

Didn't relish the idea of ordering a converter from Astronomiser from the UK, especially if there was a backlog on parts. The Cercis Astro devices from New Jersey looked similar. Both could take a while. Both were rather expensive. The DIY project by Bill VanOrden looked quite doable. But it would take a while too. Would need to source the parts. And I really felt like I needed something now. Now.

As I looked inside the battery compartment, considering how to get leads to the contacts, gently pressing the "hidden" switch, I wondered about the grip. Would it offer easier access to contacts? When I opened the BG-E2, the magazine popped out. I noticed that while there were two pairs of contacts in the grip, the magazine only had two total. Huh. Loaded the magazine with fresh AAs and the camera worked as per usual. Oh ho. Hold the phone. Six fresh AAs would put out a combined voltage of 9! I ditched the divider and put wire leads directly to the first and last contacts inside the magazine and clicked it into place. Voila! I was finally driving the camera from a gel cell marine battery. Very happy!

I made a custom cable, taking advantage of the mini 3.5mm phone "TS" connector, with special flattened push-in connectors for inside the magazine. Buttoned everything up. Worked great.

So now, at last, I have a minimal setup for an outdoor long-duration imaging rig.