This is such a great tip I just had to share it with you. Often I will give the grandchildren new batteries for something and then later find batteries lying around. I can't tell if they are the used batteries that they didn't throw away, or extra new ones
To find out if a battery is bad or good, hold it vertically a few inches from a solid flat surface and drop it onto the surface. A good battery will not bounce and will often stay standing. A used battery will bounce several times and then fall over. Amazing, isn't it?
Here is a link to a YouTube video if you want to see a demonstration: http://www.youtube.com/watch?v=Y_m6p99l6ME