Ok I was just at Target and picked up the Energizer 15 Min charger, I noticed it was 2200 mAh wehn I got home, ANd I have seen them 2500 MAh before, What is the difference, Is it the charger that is 2200 mAh or is it the batteries? Also in these chargers can I charge other brands? Some people said the Rayovac ones are btter too? I am sorrry I am all new to this, Thanks