In reality this, quite expensive, battery is just 2 × AA batteries back to back with a plastic cage to hold them together. See below for how to "roll your own".
2 × "AA" batteries, CNB-401, FNB-59, FNB-79, MHFNB59, MH-FNB-59,
not to scale.
Height × Width × Length.
|Chemical Composition.||Nominal Voltage.|
|FNB-59.||50.5 mm × 14.5 mm × 30 mm (approx).|
This is so simple as to be unreal! Works on the Yaesu VR-500 and should work with all other models that take the same battery.
In the unlikely event that your rechargeable is of a different construction and the case is Positive (some are!), wrap a couple of turns of electricians tape around where you took the casing off to re-insulate it (check that the edge is covered too, if needs be) and, with a small piece of tin foil, wrap the base and (now insulated) case so that the foil will make contact with the Negative pole of the battery and the side contact. Then carefully fit this battery into the slot and replace the cover.
Switch on to check it is working. Then, if all is well, plug in the power lead and it will charge.