My old Aceco FC1002 frequency meter stopped working without being plugged into the charger. It runs from a quartet of NiMH cells taped into a tray I made seven years ago:
One of the cells was completely dead and the other three will blink LEDs for the rest of their lives.
The Eneloops have trickled down from the DSC-H5 and still seem perfectly fine for ordinary use.
The faceplate bears the scars of its cracked acrylic (?) coating, so I pushed it out, traced the outline on a flat piece of polypropylene clamshell packaging, cut it out, and stuck it in place with tapeless sticky:
That removes the branding, but IMO improves the appearance.
It should continue working for another half decade or so!
The Smell of Molten Projects in the Morning 