Can't Believe It

This morning my son comes out with his toy Dirt Devil vacuum cleaner.  "I need batteries," he says and sure enough he did.  The part that I can't believe came when we tested the batteries.  (No, we don't normally use a battery tester.  We just toss and replace all the batteries.)  However, being that he is only four and loves gadgets and gizmos my husband said, "Do you want to test them to make sure that's the problem?"  Well, long story short - only two out of the four "C" batteries were dead.  The other two registered that they had a full charge.  How? I don't know, but if this is the case with many of the things that we replace the batteries in, I wonder just how many times we have thrown out perfectly good batteries?  This morning really opened our eyes and we will be checking each battery before tossing from now on.