Water bottles are much cheaper than batteries. For example, suppose that after a natural disaster some people are left without water and without power. It make

Water bottles are much cheaper than batteries. For example, suppose that after a natural disaster some people are left without water and without power. It makes perfect sense to load some water bottles into a truck and drive over there to help them, but it would be very impractical to load a truck with enough batteries to make even a tiny bit of difference.