I took out my old Minelab GP Extreme from the year 2000 to give it a try in the forest. But soon I realized how cumbersome and heavy that lead acid battery strapped to your hip was. The GP Extreme is still a pretty good detector but the battery system is not comfortable at all.
Btw. all files for 3d printing etc. can be found at the bottom of this post, just scroll down.
I begun to think which batteries I could use that I already own. Like others I used my NP-F960 camera batteries that have a nominal voltage of 7.2 Volts (fully charged 8.4V) and with a capacity of 6600 mAh they last about 7 hours. For me that is plenty enough.
Long story short I acquired a cheap step-down switching voltage regulator with 3A (D-SUN MP1584EN) and with a frequency of 1.5MHz, F970 battery plate and a 6.35mm headphone audio socket.
I designed a small battery case in Fusion360 and 3d printed it on my Prusa MK3 with PETG filament. Connected the F970 battery plate with two bolts and nuts to the 3d printed case and mounted everything in place. The voltage regulator was adjusted with the small onboard potentiometer to output a voltage of 6.8 Volts. This is safe to operate the Minelab GP-Extreme. Now you just have to put a strip of velcro to the battery box and your NP-F960 battery and on the side of your detector.
I also repaired my vintage Garrett Headphones with 3d printed parts. The old plastic bracket was damaged and didn’t hold well. You can find the link to my files at the bottom of this post.