This scale originally had a CR2032 in it and I had some solar cells just laying around...
With me feeling that a solar cel not being used is Soooo un-green.. I had to put them to work. Here is what I came up with. I really like this scale so it became the target of an upgrade. Due to the design of this scale, I was able to mount this device by just wedging in under the twisted arms. NO, this does NOT screw or alter the weighing sensors because they are mounted on the bottom of the scale feet. I didn't cut a slot for the exiting cable to where the CR2032 was originally housed. this allows you to either exit on top where I did, or hidden at the bottom.

The designed for Solar cells are 52 x 52 mm and put out 2.0v each.
A normal CR2032 is 3v.

With two AA's at 1.5v each and a diode to make sure the power only goes into the batteries rather than out, the voltage drop of the diode should bring the voltage really close to a good charging voltage for the two AA's in series.

Scale - ------[Cel 1]+-------[Cel 2]+-------[ Diode ]----- Scale +

Scale - ------[Bat 1]+-------[Bat 2]+----------------------- Scale +

I printed with supports and had the part I'd see all the time up so it had the best finish.
Even if your bottom looks bad, it's ok because you will never see it. :) I don't normall look under my scale.... :P