"Renata" wrote in message
...

The batteries are probably past their prime, in spite of not a whole
lot of use. They're the 18v Milwaukee, NiMh I believe, and probably
about 3 years old.


3 years is the average.

Keep in mind also that larger voltage batteries have more cells packed
inside the battery case and heat is an enemy to these cells. Because there
are many more cells in an 18 volt battery vs. a 9.6 or 12 volt battery you
have more cells insulating the inner cells during heavy use and recharging.
It is an inherent fact that the more cells a battery has and the way they
are packaged in the battery pack the shorter life span they will have when
compared to the lesser voltage ones. Basically, what you gain in longer run
times and power you loose in life expectancy with all things being equal.