Can anyone tell me the best way to clean the contacts on both the batts AND the wall charger? I noticed a marked decrease in how long 3 of my batts lasted today, so I think it's time to clean the contacts. Do I just use rubbing alcohol and some q-tips, or should I just wipe them down. I see that I'm getting black crud in the contact areas of the batteries. I can't see if anything is building up in the charger contact, but I'd like to clean it out anyway if it's possible.