Quote Originally Posted by jim10219 View Post
A CR123 is a 3v battery. AA's are 1.5v a piece. So you'd basically just have to buy a 2x AA battery holder (they're almost always wired in series) and connect the + of the AA battery back to the + terminal of the light meter, and the - wire off the battery pack to the - of the battery terminal in the light meter. Easy. The hard part will be figuring out where to hold the additional battery pack.

You might want to buy lithium AA batteries for this. If this thing is draining batteries fast, those will not only last longer, but they're made with a similar technology as the CR123's, so they should have a similar discharge curve. This might be important if the Sekonic doesn't have some kind of voltage regulation system installed (like a Wheatstone bridge) to maintain accurate light readings throughout the batteries life cycle. I've never used nor seen the inside of a Sekonic L-358, so I can't say how they're wired. But using lithium AA's would be a lot simpler of a solution than overpowering and then regulating the power supply to mimic the more stable discharge curve of lithium batteries, if it were so required.

Though I will say that none of my light meters eat batteries all that fast. So my initial inclination is that if yours is eating batteries pretty quickly, then you likely have a short somewhere (or a bad habit of leaving it on).

Thanks very much for the detailed reply. I'll definitely look into the lithium batteries.
As you correctly point out the bigger problem is how to attach the battery pack. The original poster's posting seemed to indicate that he had come up with a solution. It would be good to hear from him and see his solution.

Regards, don