Not really… it’s just old age setting in. Still, best not to overcharge them… they get hot when that happens. But they take overcharge better than about anything except nickel-hydrogen cells (lotsa luck finding those… most go in satellites). Nickel-hyrdogen cells are the closest thing to indestructible there is.
how about nickel-iron batteries?
you can brake those crystals apart. I used to do it, before. i used flash circuit from single use camera, and zapped each cell 3 times with high voltage impulse that was meant for neon tube of the flash.
i used to revive cells that would not take charge no more, it would fix them for a while, but after dozen or so cycles, they stop taking charge again, zapping them again fixes them again for a little while.
but it is not in any way alternative for replacing cells with good ones, just to prolong cells life a bit.
quality nicads last.
too many power tools use junk that gives the chemistry a bad name.
i have a few that are pushing 20 years.
there are 8 in moms portable radio that are from 1971.
old ge d cells with a whopping 3.2ah!
were are letting her run em till they give up.
offered her some panasonic 8ah nimh but she also wants to see how much longer they will go.
it ran a week on a charge during the power outage from ike.and again was still going after 4 days from the derecho we had 2 years ago.