RE: Power Panel for I40
If you do the math, it will take the power panel3 or4 years to pay for itself at the prices I've seen. (around $70) By that time the rechargeable battery in the power panel will probably need replaced.
I've had mine out for a full year and part of that time it was over a feeder taking 2,000+ pictures a month. I would guess it has taken 8,000 pictures in the last year. It took over 5,000 pictures on the first set of batteries and lasted 5 months. I'm probably going to put in the 2nd set of batteries when I check it this month, it was down to 35% last time I checked it.
I've thought about making my own power panels for some of my cameras, a decent 12v battery and a small solar panel will run around $35 - $40 then a box and you're up to $50 so not really much savings there either.
Probably the most economical solution is just buying D cell batteries in bulk. Also the Rayovacs seem to last just as well as the Duracells and Energizers to me and are about 50% cheaper.