Owning jumper cables is like owning a truck. When you own a truck, people seem to cozy up to you when they are moving. When you own jumper cables, you're suddenly like Batman but for dead batteries. You might as well give your friends a Jumper Cables Signal that they can point at the cloudy sky in times of crisis. With great power comes great responsibility, I guess. (And now I am mixing metaphors.)
Car batteries are full of toxic chemicals and have to be dealt with specially when they die. The green thing to do is to squeeze as much life out of them as possible and decrease the overall amount of batteries that you are going to need in your lifetime. Here are some tips for that.