What problem is the OP trying to solve? Self-discharge? inability to charge? low voltage (shorted cell)? "Wearout" for a battery usually means it's been charged and discharged as many times as it can be, and is not capable of providing an acceptable performance profile any more. All secondary or storage cells have a finite cycle life. Sometimes and for some battery technologies the cells can be reformed, but I'm not sure about current products.
If they've just had the stuffing used up, he just needs a replacement that at least meets the OEM specs, or to use up a lot of primary cells (alkalines or similar) making do without his recharging ability.