There has been more interest in this Mod., however the text has went missing and I am reposting.
Photos showing modification of my Whites Eagle Sprectrum battery holder from C to AA cells are above.
Photo-1: Machining out the top with a 3/16” end mill. Made the hole about 1/8” larger than the Mouser 6 cell holder (#12BH364-GR with wires) to be added. No need for high precision and I did not use an edge finder, only machining at the line. A Dremel type multi-tool might work just as well.
Photo-2: The rear contacts have been drilled out, retaining tabs cut off, and the back glued in with PVC cement. In retrospect, there could have been more rigidity in the previous machining process if this step had been done first.
Photo-3: Springs on the front have been snipped off and a spot of solder applied to each contact.
Photo-4: I thought the Mouser holder would set too far down into the existing holder so placed 3/8” plywood spacer strips between the reinforcing ribs of the Whites. There is an opportunity for further weigh reduction here by not using them, but one would have to dig the batteries out with their fingernails. Alternatively, using a lighter weight material like corrugated plastic is possible. Anyway, if only strips of the VHB (Very High Bond) tape are used, be sure that they are built up thicker than the reinforcing ribs for good adhesion to the Mouser part.
Photo-5: The wires were soldered on and new holder stuck to the VHB tape strips. This battery pack checks 6.7V with the dummy battery and 8.1V with all 6 cells. My detector seemed to work OK at 8.1V, but I don’t know what maximum input voltage it’s regulator circuit can handle. Maybe someone from Whites will advise on this subject.